ABSTRACT XIE, HANG. the Role of Fiber Type in Performance of Their Composites from 3D Orthogonal Woven Preforms

ABSTRACT XIE, HANG. The Role of Fiber Type in Performance of their Composites from 3D Orthogonal Woven Preforms. (Under the direction of Dr. Abdel-Fattah M. Seyam) Composite materials become more and more important in many fields such as the aerospace industry, construction and automobile industry as they can provide numerous advantages and new concepts for the replacement of traditional materials. Also, composite materials have different types and the fiber reinforced composites with improved mechanical properties are widely in use. In fiber reinforced composite materials, fibers and resin matrix are two distinct phases with separately physical and chemical properties. However, the combinations of them offer the various properties to meet different requirements. The fibers are working as the major roles in determination of the fiber reinforced composite material strength, and the matrix can provide the protection from damage, hold the fibers in the right position and transfer the load. High performance polymeric fibers such as ultra-high molecular weight polyethylene fibers, PBO fibers and liquid crystal polymer fibers have relatively high specific tensile strength and modulus when compared with other high performance fibers which lead them being considered as suitable fibers to reinforce composite with providing great mechanical properties and weight saving characteristic.

In this research, several high performance fibers: ultra-high molecular weight polyethylene with brand name Spectra®, liquid crystal polymer polyarylate fiber with brand name Vectran®, PBO fiber with brand name Zylon® and E-glass were used to form composites from 3D orthogonal preforms.

The y- and z-tows of the 3D orthogonal woven preforms were E-fiber glass. The Spectra®, Vectran® and

Zylon® fibers in tow forms were inserted in the x-direction by using 3D weaving machine (donated by

3TEX Inc.) available in the composite core facility at the NCSU College of Textiles. Resin infusion of the preforms were conducted by using the method of Vacuum Assisted Resin Transfer Molding (VARTM) with the assistance of VacMobiles® 20/2 VARTM equipment, which is also available at the composite core facility. The final composites’ performance were tested for their impact performance (Tup impact, Izod impact and Charpy impact) and tensile strength in x- and y-directions. Additionally, analytical property such as thickness, constituents’ and total fiber volume fraction and preform areal density, composite areal

density were determined to understand the role of fiber type in the performance of their composites. This was achieved by comparing the fiber and yarn tensile properties to their corresponding composites. The role of fiber in determining the impact properties of composite was also revealed by comparing the tensile energy required to break the fibers with the energy required to break their corresponding composites.

It was found out that Zylon® has the best tensile performance as single fiber with highest tensile tenacity and modulus among those high performance fibers used in this research, while the Spectra® and Vectran® exhibited little difference in the tensile modulus and tenacity of single fiber.

When considering the yarn tensile strength, the tensile modulus of Zylon® yarn is as dominating as the tensile modulus of its single filament. However, the tenacity of Zylon® yarn is not the highest but as second highest that lower than Spectra® yarn While the data from yarn tensile results indicate this, the statistical analysis shows no difference between their tenacity. The composite tensile strength testing results indicate that, in x-direction testing that composite specimens with Zylon® fibers have the outstanding tensile peak load and stress when compared with other composite specimens from Spectra® and Vectran® fibers, and even the peak load and peak stress that normalized by the preform areal density and composite areal density also indicate composites with Zylon® fibers have better performance. For tensile testing in y-direction, the testing results shows no significant difference from the statistical analysis since y- and z-yarns are from E- glass. Other mechanical testing such as Tup impact testing, Izod impact testing and Charpy impact testing were also conducted to examine energy related properties of the composite materials reinforced with each type of high performance fibers. For Tup impact, testing results indicate that composites with Zylon® fibers in x-direction have the best Dynatup impact resistance and impact strength among the high performance fibers used as x-yarns in this research.

The Role of Fiber Type in Performance of their Composites from 3D Orthogonal Woven Preforms

by Hang Xie

A dissertation submitted to the Graduate Faculty of North Carolina State University In partial fulfillment of the requirements for the Degree of Master Science

Textiles

Raleigh, North Carolina

2016

APPROVED BY:

______Dr. Yingjiao Xu Dr. Moon Suh Committee Member Committee Member

______Dr. Abdel-Fattah Mohamed Seyam Chair of Advisory Committee

BIOGRAPHY

Hang Xie was born in Hubei, China. He graduated from Polymer Science and Engineering Department in

Qingdao University of Science and Technology in 2010. After years of working, he started to pursuit a higher level education as a master student in College of Textiles, NC State University in 2013 fall semester.

ACKNOWLEDGEMENTS

I would like to express my sincere gratitude to Dr. Abdel-Fattah M. Seyam for his funding as well as his continuous encouragement and guidance throughout the period of my study. I’m grateful to Dr. Moon Suh and Dr. Yingjiao Xu for their guidance and valuable suggestions. Thanks to Teresa White, Dr. Jan Ballard and Mr. Jeffrey Krause for the convenience and guidance in their labs. Also, I would like to thank Dr. Rahul

Vallabh, Mr. Mohamad Midani (FPS PhD student) and Ms. Elizabeth-Lane Claunch (TTM PhD student) for their valuable suggestion and contribution in the 3D orthogonal weaving machine set up. Thanks to my parents for their love and support.

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TABLE OF CONTENTS

LIST OF TABLES ...... viii LIST OF FIGURES ...... x 1. Introduction ...... 1 2. Literature review ...... 4 2.1 UHMWPE fibers-Spectra® 1000 fibers ...... 5 2.1.1 Introduction ...... 5 2.1.2 Production ...... 7 2.1.3 Fiber Properties ...... 9 2.2 TLCP fiber-Vectran® HT fibers ...... 14 2.2.1 Introduction ...... 14 2.2.2 Production ...... 15 2.2.3 Fiber properties ...... 16 2.3 PBO fibers-Zylon® HM fibers ...... 20 2.3.1 Introduction ...... 20 2.3.2 Fiber production ...... 21 2.3.3 Fiber properties ...... 22 2.4 E-glass fibers ...... 27 2.4.1 Introduction ...... 27 2.4.2 Fiber production ...... 28 2.4.3 Fiber properties ...... 29 2.5 Single fiber tensile properties ...... 31 2.6 Tensile property relationship between the single fiber and yarn ...... 33 2.7 3D woven composites ...... 34 2.7.1 3D woven preforms ...... 35 2.7.2 Resin matrix ...... 38 2.7.3 3D composite mechanical properties ...... 40 3. Objective ...... 45 4. Experimental ...... 46 4.1 Single fiber and yarn tensile testing ...... 46 4.1.1 Materials ...... 46 4.1.2 Specimen preparation ...... 48

4.1.3 Tensile testing ...... 50 4.2 3D woven preform ...... 50 4.2.1 Materials ...... 50 4.2.2 3D orthogonal woven preform construction ...... 53 4.2.3 3D Woven preform thickness ...... 55 4.2.4 3D orthogonal woven preform FVFs ...... 56 4.2.5 3D woven preform areal density ...... 58 4.2.6 Composite areal density ...... 58 4.2.7 z-yarn crimp determination ...... 59 4.3 Composites formation ...... 59 4.3.1 Materials ...... 59 4.3.2 Resin infusion ...... 60 4.4 Mechanical testing ...... 62 4.4.1 Panel sampling ...... 62 4.4.2 Tensile strength testing ...... 64 4.4.3 Dynatup impact property ...... 66 4.4.4 Charpy impact property ...... 66 4.4.5 Izod Impact property ...... 68 4.5 Statistical Analysis ...... 69 5. Results and discussion ...... 70 5.1 FVFs and z-yarn crimp ...... 70 5.2 Resin infusion performance ...... 73 5.3 Cross-sections ...... 77 5.4 Single fiber tensile testing ...... 80 5.5 Yarn tensile testing ...... 86 5.6 3D orthogonal woven preform reinforced composite mechanical properties ...... 97 5.6.1 Tensile properties ...... 97 5.6.2 Composite material Dynatup impact testing ...... 128 5.6.3 Charpy Impact testing results ...... 153 5.6.4 Composite material Izod Impact testing results ...... 159 6. Conclusion and recommendation for future studies ...... 165 References ...... 168 APPENDICES ...... 174

APPENDIX A: Yarn linear density determination testing ...... 175 APPENDIX B: Measured thickness of 3D orthogonal woven preform...... 176 APPENDIX C: Composite areal density measurements...... 177 APPENDIX D: Fiber surface area ...... 178 APPENDIX E: Single fiber tensile testing results tables ...... 179 Table E.1 All specimens for Spectra® single fiber tensile testing ...... 179 Table E.2 All specimens for Vectran single fiber tensile testing ...... 180 Table E.3 All specimens for Zylon single fiber tensile testing ...... 181 Table E.4 All specimens for Fiber Glass 275 tex single fiber tensile testing ...... 182 Table E.5 All specimens for Fiber Glass 735 tex single fiber tensile testing ...... 183 Table E.6 All specimens for Fiber Glass 2400 tex single fiber tensile testing...... 184 APPENDIX F: Yarn tensile testing result tables ...... 185 Table F.1 All specimens for Spectra® yarn tensile testing ...... 185 Table F.2 All specimens for Vectran yarn tensile testing ...... 186 Table F.3 All specimens for Zylon yarn tensile testing ...... 187 Table F.4 All specimens for Fiber Glass 275 tex yarn tensile testing ...... 188 Table F.5 All specimens for Fiber Glass 735 tex yarn tensile testing ...... 189 Table F.6 All specimens for Fiber Glass 2400 tex yarn tensile testing ...... 190 APPENDIX G Orthogonal woven preforms reinforced composite tensile testing results ...... 191 Table G.1 Specimens for Spectra Panel 2, extensometer used...... 191 Table G.2 Specimens for Vectran Panel 2, extensometer used...... 192 Table G.3 Specimens for Zylon Panel 2, extensometer used...... 193 APPENDIX H Tup impact testing results tables ...... 194 Table H.1 Normalized peak force for Spectra® ...... 194 Table H.2 Normalized energy for Spectra® ...... 195 Table H.3 Normalized peak force for Vectran® ...... 196 Table H.4 Normalized energy for Vectran® ...... 197 Table H.5 Normalized peak force for Zylon® ...... 198 Table H.6 Normalized energy for Zylon® ...... 199 APPENDIX I Charpy impact testing results tables ...... 200 Table I.1 Charpy impact specimens for Spectra® in X direction ...... 200 Table I.2 Charpy impact specimens for Spectra® in Y direction ...... 201 Table I.3 Charpy impact specimens for Vectran in X direction...... 202

Table I.4 Charpy impact specimens for Vectran in Y direction...... 203 Table I.5 Charpy impact specimens for Zylon in X direction ...... 204 Table I.6 Charpy impact specimens for Zylon in Y direction ...... 205 Table I.7 Tukey multiple comparison ANOVA table for Charpy impact resistance (REL) in x- direction...... 206 Table I.8 Tukey multiple comparison ANOVA table for Charpy impact strength (RE) in x-direction...... 206 Table I.9 Tukey multiple comparison ANOVA table for Charpy impact resistance (REL) in y- direction...... 207 Table I.10 Tukey multiple comparison ANOVA table for Charpy impact strength (RE) in y- direction...... 207 APPENDIX J Izod impact testing result tables...... 208 Table J.1 Izod impact specimens for Spectra® in X-direction ...... 208 Table J.2 Izod impact specimens for Spectra® in Y-direction ...... 208 Table J.3 Izod impact specimens for Vectran in X-direction ...... 209 Table J.4 Izod impact specimens for Vectran in Y-direction ...... 209 Table J.5 Izod impact specimens for Zylon in X-direction ...... 210 Table J.6 Izod impact specimens for Zylon in Y-direction ...... 210 Table J.7 Tukey multiple comparison ANOVA table for Izod impact resistance (REL) in x-direction...... 211 Table J.8 Tukey multiple comparison ANOVA table for Izod impact strength (RE) in x-direction.211 Table J.9 Tukey multiple comparison ANOVA table for Izod impact resistance (REL) in y-direction...... 212 Table J.10 Tukey multiple comparison ANOVA table for Izod impact strength (RE) in y-direction...... 212

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LIST OF TABLES

Table 1 Strength retention of Vectran® HS fiber after chemical exposure [22] ...... 19

Table 2 Typical fiber-forming E-glass compositions [7] ...... 28

Table 3 Published yarn data...... 47

Table 4 Yarn linear density testing results...... 48

Table 5 Calculated maximum filling density for each high performance fiber ...... 53

Table 6 Comparison between the measured preform thickness and the theoretical thickness ...... 56

Table 7 Theoretical FVFs for preforms with different type of high performance fibers ...... 57

Table 8 Preforms’ areal density measurement ...... 58

Table 9 Composite specimen areal density measurement ...... 59

Table 10 Additive in resin system (a) Typical liquid resin properties of Derakane 8084, (b) Typical properties of initiator NOROX MEKP-925H ...... 60

Table 11 Typical Gel Times Using NOROX MEKP-925H and Cobalt Naphthenate-6% ...... 61

Table 12 Minimum size of the repeat unit for preforms with each high performance fibers ...... 64

Table 13 Total infusion time for each type of high performance fiber ...... 75

Table 14 Fiber surface area ...... 76

Table 15 Single fiber tensile properties comparison ...... 85

Table 16 Comparison of the high performance fibers yarn tensile properties ...... 92

Table 17 Tukey multiple comparison ANOVA table for modulus of single fiber and yarns. (a) and (b) .. 95

Table 18 Tukey multiple comparison ANOVA table for tenacity of single fiber and yarns. (a) and (b) ... 96

Table 19 Tenacity comparison...... 110

Table 20 Tukey multiple comparison ANOVA table for peak stress in x-direction. (a) and (b) ...... 117

Table 21 Tukey multiple comparison ANOVA table for peak stress in y-direction...... 117

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Table 22 Tukey multiple comparison ANOVA table for peak force normalized with composite areal density. (a) and (b)...... 144

Table 23 Tukey multiple comparison ANOVA table for energy normalized with composite areal density.

(a) and (b) ...... 145

Table 24 Summary Dynatup impact results with peak force normalized ...... 146

Table 25 Summary Dynatup impact results with energy normalized...... 146

Table 26 The Charpy Impact testing results for each type of high performance fibers in X direction and Y direction. (a) Specimens in Y direction; (b) specimens in X direction...... 155

Table 27 Tukey multiple comparison ANOVA table for Charpy impact resistance (REL) in x- and y- direction. (a) and (b) ...... 156

Table 28 Tukey multiple comparison ANOVA table for Charpy impact strength (RE) in x- and y- direction. (a) and (b) ...... 157

Table 29 Break types for Izod impact test ...... 159

Table 30 The Izod impact testing results for each type of high performance fibers in different directions.

...... 162

Table 31 Tukey multiple comparison ANOVA table for Izod impact resistance (REL) in x- and y- direction...... 163

Table 32 Tukey multiple comparison ANOVA table for Izod impact strength (RE) in x- and y-direction.

...... 164

LIST OF FIGURES

Figure 1 Chemical structures of the four high performance fibers. (a) Ultra high molecular weight polyethylene (UHMWPE), (b) Polyarylate (PAR), (c) Poly (p-phenylene-2, 6-benzobisoxazole) (PBO),

(d) glass fiber (SiO2) ...... 5

Figure 2 Gel-spinning process schematic [11] ...... 8

Figure 3 Schematic illustration of UHMWPE fiber's structural hierarchy [13] ...... 9

Figure 4 UHMWPE fiber tensile property vs. crystallinity. (a) Breaking strength vs. crystallinity; (b) initial modulus vs. crystallinity [15] ...... 10

Figure 5 Strength based on weight vs strength based on volume of various fibers. [7]...... 11

Figure 6 Abrasion and flex life of various fibers. [7] ...... 12

Figure 7 UV resistance of high performance fibers. [7] ...... 13

Figure 8 Schematic diagram of the liquid crystal polymer chain structure [22] ...... 16

Figure 9 TLCP parallel strand rope stress relaxation. Whitehill Manufacturing Corporation

WMCJETS/JETSTRAN 1-A VEC ½” Rope. [7] ...... 17

Figure 10 Tensile strength vs flexural fatigue of Vectran HS and aramids. [7] ...... 18

Figure 11 Comparison of tenacity retention of Vectran HS and Kevlar 29 in different situation. (a)

Tenacity retention after thermal exposure; (b) Comparison of tenacity of Vectran® HS and Kevlar® 29 at elevated temperatures [22] ...... 19

Figure 12 Simplified schematic of PBO polymerization. [7] ...... 21

Figure 13 PBO fiber structure model [7] ...... 22

Figure 14 Specific strength vs. specific modulus for various fibers. [7] ...... 23

Figure 15 Tensile strength dependence on gage length for cis-PBO fibers (0.02/min strain rate and twists/in.) [32] ...... 24

Figure 16 Dependence of tensile strength and modulus on twists/in for 130 denier cis-PBO fiber bundles.

(0.02/min. strain rate and 5 inch gauge) [32] ...... 25

Figure 17 Comparison of PBO cyclic behavior with polyester, aramid and HMPE in terms of applied stress [33] ...... 25

Figure 18 SEM micrograph of the untreated AS type PBO fiber [36] ...... 26

Figure 19 Schematic of direct melt process for production of continuous filament. [7] ...... 29

Figure 20 SEM images of some E-glass fiber fracture surfaces. [39]...... 30

Figure 21. Typical tensile stress-strain curves for the PBO, PPTA, PPODTA, PAR, PE and PLA high performance polymeric fibers. (a) PBO fibers, (b)PPTA fibers, (c)PPODTA fibers, (d)PAR fibers, (e)PE fibers, and (f)PLA fibers. [40] ...... 32

Figure 22 Distribution of filaments according to their TBALF (tenacity based on average load on filaments) [42] ...... 34

Figure 23 Classification of 3D fabrics based on weaving technique [45] ...... 35

Figure 24 Architecture of 3D orthogonal woven fabric with plain weave and 4 layers [44] ...... 36

Figure 25 Broken filaments passing through the guide [46] ...... 37

Figure 26 Cumulative probability distribution plots of the tensile strength of a 300 tex E-glass yarn determined after different stages of the 3D weaving process. The average tensile strength value of the yarn after each weaving stage is shown. [46] ...... 37

Figure 27 Comparison of thermoset and thermoplastic polymer structures. [48] ...... 39

Figure 28 Effect of fluid pressure on compaction in vacuum infusion. [50] ...... 39

Figure 29 Load elongation curve of different structures. [51] ...... 41

Figure 30 Bar diagram for impact properties of different structures. [51] ...... 41

Figure 31 Schematic depictions of various interactions at the fiber-matrix interface: (a) micromechanical interlocking, (b) permanent or induced dipole interactions, (c) chemical bonding, (d) chain entanglement and (e) transcrystallinity [49] ...... 42

Figure 32 Section view of the specimens after 50 J repeated impact test [54] ...... 43

Figure 33 Schematic illustrations of foreign object damage in (a) the 3D CMC without spall, (b) the 3D

CMC with spall, (d) the 2D CMC without perforation and (e) the 2D CMC with perforation and plain views of (c) the 3D CMC and (f) the 2D CMC [56] ...... 44

Figure 34 Single fiber tensile testing preparation (a) dimensional size of the cardboard frame, (b) actual cardboard frame, (c) specimen mounted between the grips in gauge length ...... 49

Figure 35 View of the 3D weaving machine ...... 51

Figure 36 3D woven fabric surface. (a) Spectra®; (b) Vectran®; (c) Zylon®...... 52

Figure 37 Structure of 3D orthogonal preform. [55]...... 54

Figure 38 Cutting plan for the mechanical testing specimens ...... 63

Figure 39 Composite Tensile property tester. (a) Tensile property tester; (b) Hydraulic power unit ...... 65

Figure 40 Tup impact property tester...... 66

Figure 41 Charpy Impact tester. (a) Instron® Ceast 9050 Impact tester; (b) Charpy impact testing table. 67

Figure 42 Izod Impact property tester. (a) tester; (b) hammer; (c) clamping table...... 68

Figure 43 Dry preform thickness compared with composite thickness ...... 71

Figure 44 Fiber volume fractions for each type of high performance fibers. (a) x-yarns; (b) y-yarns; (c) z- yarns...... 71

Figure 45 Z yarn crimp ...... 73

Figure 46 Infusion resin flow front lines and time. (a) Spectra®; (b) Vectran®; (c) Zylon®. Blue arrows indicate the resin flow direction...... 74

Figure 47 Infusion resin flow front line distance to the inlet...... 76

Figure 48 X-direction ross-sections of composites with different type of high performance fibers. (a)

Spectra®; (b) Vectran®; (c) Zylon®...... 77

Figure 49 Y-direction cross-sections of composite with different type of high performance fibers. (a)

Spectra®; (b) Vectran®; (c) Zylon®...... 79

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Figure 50 Tensile behavior curves for the high performance single fiber. (a) Spectra® fibers, (b)

Vectran® HT fibers, (c) Zylon® HM fibers, (d) fiber glass from yarn with linear density 275 tex, (e) fiber glass from yarn with linear density 735 tex, (f) fiber glass from yarn with linear density 2400 tex...... 81

Figure 51 Typical high performance fibers tensile behavior ...... 84

Figure 52 Tensile curves for the yarns of high performance fibers. (a) Spectra®, (b) Vectran®, (c)

Zylon®, (d) fiber glass with linear density 275 tex, (e) fiber glass with linear density 735 tex, (f) fiber glass with linear density 2400 tex...... 87

Figure 53 Comparison of the typical tensile behavior between the single fiber and yarn. (a) Spectra®, (b)

Vectran®, (c) Zylon®, (d) fiber glass with linear density 275 tex, (e) fiber glass with linear density 735 tex, (f) fiber glass with linear density 2400 tex...... 90

Figure 54 Typical tensile behavior of the yarns from high performance fibers ...... 91

Figure 55 Original load-strain curves...... 98

Figure 56 Modified load-strain curves ...... 100

Figure 57 Modified load-strain curves of composite with Spectra® in x-direction. (a) Load normalized by preform areal density; (b) load normalized by composite areal density...... 102

Figure 58 Modified load-strain curves of composite with Vectran® in x-direction. (a) Load normalized by preform areal density; (b) load normalized by composite areal density...... 103

Figure 59 Modified load-strain curves of composite with Zylon® in x-direction. (a) Load normalized by preform areal density; (b) load normalized by composite areal density...... 104

Figure 60 Typical load-strain comparison curves. (a) Modified curves; (b) normalized by preform areal density; (c) normalized by composite areal density...... 105

Figure 61 Tenacity-strain curves for composite tensile specimens in x- and y-direction. (a) Spectra®; (b)

Vectran®; (c) Zylon®; (d) E-glass fiber ...... 107

Figure 62 Typical tenacity-strain curves for specimens with different high performance fibers in x- direction and E-glass fibers in y-direction...... 109

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Figure 63 Tenacity comparison between the single fiber and Yarn...... 111

Figure 64 Tenacity comparison between the single fiber and corresponding composites...... 111

Figure 65 Tenacity comparison between the yarn and corresponding composites...... 112

Figure 66 Modified stress-strain curves for composite specimens with difference high performance fibers.

(a) specimens with Spectra® in x-direction; (b) specimens with Vectran® in x-direction; (c) specimens with Zylon® in x-direction; (d) specimens with E-glass fiber in y-direction...... 113

Figure 67 Average peak stress for each type of high performance fibers in x-direction (a) and y-direction

(b) ...... 116

Figure 68 Normalized stress-strain curves for specimens with Spectra® in x-direction. (a) Normalized by preform areal density; (b) normalized by composite areal density...... 119

Figure 69 Normalized stress-strain curves for specimens with Vectran® in x-direction. (a) Normalized by preform areal density; (b) normalized by composite areal density...... 120

Figure 70 Normalized stress-strain curves for specimens with Zylon® in x-direction. (a) Normalized by preform areal density; (b) normalized by composite areal density...... 121

Figure 71 Typical stress-strain comparison and normalized stress-strain curves. (a) Stress-strain curves;

(b) stress-strain curves normalized by preform areal density; (c) stress-strain curves normalized by composite areal density...... 122

Figure 72 Composite strains for composites with different type of high performance fibers. (a) x-direction for polymeric fibers; (b) E-glass fiber ...... 124

Figure 73 Break energy comparison between the single fiber and yarn...... 126

Figure 74 Break energy comparison between the single fiber and corresponding composites...... 126

Figure 75 Break energy comparison between the yarn and corresponding composites...... 127

Figure 76 Broken composite tensile specimen in Y-direction...... 128

Figure 77 Specimens after preliminary Dynatup impact tests. (a) Spectra® in X-direction; (b) Vectran® in

X-direction; (c) Zylon® in X-direction...... 129

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Figure 78 Force-displacement curves for each type of high performance fibers. (a) Spectra®; (b)

Vectran®; (c) Zylon®...... 130

Figure 79 Force-displacement curves for each type of high performance fibers normalized with composite thickness. (a) Spectra®; (b) Vectran®; (c) Zylon®...... 131

Figure 80 Force-Displacement curves of individual specimen for each type of high performance fibers normalized with 3D orthogonal preform areal density. (a) Spectra®; (b) Vectran®; (c) Zylon®...... 133

Figure 81 Force-Displacement curves of individual specimen for each type of high performance fibers normalized with composite areal density. (a) Spectra®; (b) Vectran®; (c) Zylon®...... 135

Figure 82 Energy-Displacement curves of individual specimen for each type of high performance fibers.

(a) Spectra®; (b) Vectran®; (c) Zylon®...... 137

Figure 83 Energy-Displacement curves of individual specimens for each type of high performance fibers normalized with composite thickness. (a) Spectra®; (b) Vectran®; (c) Zylon®...... 139

Figure 84 Force-Displacement curves of individual specimen for each type of high performance fibers normalized with preform areal density. (a) Spectra®; (b) Vectran®; (c) Zylon®...... 140

Figure 85 Energy-Displacement curves of individual specimens for each type of high performance fibers normalized with composite areal density. (a) Spectra®; (b) Vectran®; (c) Zylon®...... 142

Figure 86 Typical Force-Displacement curves for composite with each type of high performance fiber 147

Figure 87 Typical normalized Force-Displacement curves for composite with each type of high performance fiber. (a) Peak force normalization with thickness; (b) peak force normalization with 3D orthogonal preform areal density; (c) peak force normalization with composite areal density...... 148

Figure 88 Typical Energy-Displacement curve for composite with each type of high performance fibers

...... 150

Figure 89 Typical normalized Energy-Displacement curves for composite with each type of high performance fiber. (a) Energy normalization by thickness; (b) energy normalization by 3D orthogonal preform areal density; (c) energy normalization by composite areal density...... 151

Figure 90 Tup specimens of composite reinforced by Spectra in x-direction. (a) Top view; (b) side view.

...... 152

Figure 91 The pictures of composite specimens for Charpy Impact. (a) y-direction; (b) x-direction ...... 153

Figure 92 Specimens of composites reinforced by Vectran in x-direction for Izod impact tests. (a) x- direction; (b) y-direction...... 161

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1. Introduction

When compared to conventional materials, composite materials can offer numerous advantages and the concept of composite structures were mainly applied to create tools or weapons with improved properties in early human history [1]. High performance fibers are important constituent in producing high performance composite materials that vitally suitable materials for military technology, aerospace industry and civilian economy, as high performance composite materials can provide numerous advantages and new concepts for the replacements of traditional materials. The high performance fibers that used in composites have covered a wide range of chemical substances, including carbides and oxides which are inorganic and organic polymers. In fiber reinforced composite materials, fibers and resin matrix are two distinct phases with separately physical and chemical properties. The combinations of them offer the material improved overall properties by the components that can benefit each other while maintaining their own properties.

Generally, fiber reinforced polymer composites consist of the fibers and polymer resin that mixed and bonded on a macroscopic scale with distinct phases having recognizable interfaces between them [2]. The components of composite materials can be defined as reinforcement and matrix. The forms of reinforcement can be fibers, particles, fillers, etc. and the matrix materials can be the polymers, metals, ceramics, etc. In high performance fiber reinforced composite materials, fibers are the major load carriers while embedded and protected in matrix materials, and matrix holds the reinforcement in right position with designed shape and size. Fiber glass, polymeric fibers and carbon fibers are most commonly used high performance fibers in the fiber reinforced composite materials.

Polymers are large molecules composed of many repeated subunits that a covalently bonded in a linear form [3]. The synthesis of polyhexamethylene adipamide, commonly known as nylon 66 followed by its cousin nylon 6 made the major development in synthetic polymer fibers [4]. Since the demand of synthetic fibers keeps increasing, many polymers were synthesized over the decades and some of them are introduced as high performance fibers to satisfy the requirement in different fields. Also, efforts have been continuing on improving and developing of ultra-high performance fibers. In polymer fibers, covalent bonds in these

1 polymer molecules characterize the polymer fibers with high strength. However, synthetic polymer fibers are always exhibiting lower tensile strength than that of their theoretical potential strength, for example, the maximum modulus of the polyamide fibers only achieve 1/20 of their theoretical value [3]. Ultra-high molecular weight polyethylene (UHMWPE), isotactic polypropylene and Kevlar® are fibers that exhibit strength that is close to the theoretical values. In high performance fiber reinforced composites, high fiber tensile strength will lead to composite materials with high tensile performance.

For the matrix materials, even the fibers work as the major role in determining the strength of a fiber reinforced composite material, the selection of the matrix will characterize the composite with some important features such as the maximum service temperature, suitable process methods, durability of usage and the compressive property of the composites. There are several types of composite based on matrix materials that include the polymer matrix as applied for polymer matrix composites (PMCs), metal matrix for metal matrix composites (MMCs) and the ceramic matrix for ceramic matrix composites (CMCs) [2].

The selection of the matrix has significant influence on the interlaminar shear as well in plane shear properties of the composite materials. The interlaminar shear strength is the important factor to influence the composite structure design when the material have the bending load applied and the damage tolerance design [4]. The processing characteristics including the precursor material viscosity, the curing temperature and the curing time will determine the process approach and the defects in the final composite material.

The functions of matrix in a fiber reinforced composite are including protecting the fiber surface from mechanical degradation, keep the fiber in place to transfer the stresses between the fibers and providing a barrier to insulate the fibers from the environmental damage such as the chemicals, microbes and moisture.

Traditionally, fiber reinforced composite materials are produced as laminates that matrix material is reinforced by long fibers and to meet the mechanical requirement, the composites are designed by different thickness by stacking layers on each other and the combination of different fiber directions. Laminated composites have excellent in-plane strength but limited out-of-plane strength which lead them to have weak shear strength between the laminas. Delamination is a commonly failure in laminated composites because

2 the out-of-plane strength is only provided by the matrix material and bonding materials between the laminas.

3D fiber reinforcements are introduced to improve the out-of-plane strength of fiber reinforced composite materials. When compared with laminated composites, 3D fiber reinforced composites have advantages such as eliminate potential dimensional variation, directly manufacturing of preforms and improved delamination resistance. Typically, 3D fiber reinforcements have three sets of yarns including warp yarns, weft yarns and z-yarns in three orthogonal directions. Warp yarns and weft yarns can also be named as y- yarns and x-yarns. Three yarns in different direction provided the possibility to obtain many combination of different type of yarns. The goal of this study is to reveal the role of fiber type in determining the performance of their corresponding composite materials. To achieve the goal, composite structures from

3D orthogonal woven preforms from E-glass fibers in y-, z- directions and different high performance polymeric fibers (Spectra®, Vectran® and Zylon®) in x-direction were formed. The fiber tensile properties as well as the final composites’ properties were compared and contrasted to reveal the fiber type of role.

Additionally, Tup impact resistance, Izod impact and Charpy impact strength were examined and analyzed to compare impact resistance performance of 3D orthogonal woven composites and explain their behavior in term of fiber properties.

2. Literature review

For decades, fiber reinforced composites have been widely used in structural applications that demanding high-performance mechanical properties, they are important industrial products and have promoted the development of high performance fibers throughout the period. High performance fibers can be effectively classified by the matrix used to support them with corresponding temperature rating: polymeric matrix, which have temperature rating as high as 800 ºF, metal matrix with temperature rating range of 1500 ºF to

2500 ºF, and ceramic matrix with temperature rating range of 2000 ºF to 3000ºF. In 1991, reinforced plastics in United States had the market of approximately 2.3 billion pounds with the economy value at about $2.5 billion which indicating the high economy value with relatively low-volume [5]. Advance composites, which are defined as composites that utilize high performance fiber reinforcements, may contain amount of fibers in weight percentage as high as 50% to 70%. Also, polymeric matrix composites have the largest share of the advanced composites market, and the advanced composite market will keep expanding as their economy and industrial value have been highly recognized.

Glass fiber is the oldest high performance fiber, which is inorganic and has been manufactured since the

1930s. Nowadays, glass fibers are widely used in applications including insulation, fire resistant fabrics and reinforcement for fiberglass reinforced composites such as bathtub and boats.

In this research, the tensile testing of single fibers, yarns and final composites that reinforced by the 3D orthogonal woven preforms are determined to reveal the role of fibers in the final composites performance.

The 3D orthogonal woven preforms are woven by using different high performance fiber in different directions. The high performance fibers used in this research are Spectra®, Vectran®, Zylon® and E-fiber glass. The single fiber tensile testing was conducted to understand the tensile behaviors of different type of high performance fibers. The yarn tensile testing was conducted to examine how the tensile properties of single fiber can be represented into yarns and final 3D orthogonal preform reinforced composites. For this reason, literature review was conducted relevant to understand the fibers’ microscopic structure, production

4 method and tensile properties, the relationship between the single fiber tensile strength and the yarn tensile strength, and the tensile strength of produced composite materials.

This section provides fiber production, physical and chemical properties of E-glass, Spectra®, Vectran® and Zylon® fibers. Figure 1 shows the chemical structure of the four high performance fibers used in this research.

(a) (b)

Figure 1 Chemical structures of the four high performance fibers. (a) Ultra high molecular weight

polyethylene (UHMWPE), (b) Polyarylate (PAR), (c) Poly (p-phenylene-2, 6-benzobisoxazole) (PBO),

(d) glass fiber (SiO2)

2.1 UHMWPE fibers-Spectra® 1000 fibers

2.1.1 Introduction

Ultra-high molecular weight polyethylene (UHMWPE) fibers, which is under the trade name Spectra®,

Dyneema® and Tekmilon®, Spectra® are currently commercially manufactured with gel spinning method by Honeywell International Inc. in the USA [6]. Gel spinning produces highly oriented fibers with relatively high parallel orientation, which can be as high as 95%-99%, and high crystallinity up to 85% when compared to melting produced polyethylene which has crystallinity less than 60%. Due to the extremely

5 high viscosity of polyethylene melt, spinning UHMWPE fibers from the melting spinning is almost impossible. Additionally, the draw ratio cannot be high due to the very high degree of entanglement of the molecular chains a matter that cause relatively low crystallinity and chain orientation and as such performance will not reach the desired level [7]. And the highly oriented polyethylene(PE) fibers that are produced in gel spinning offer a combination of high stiffness and strength with low specific gravity that make these fibers are suitable for fiber reinforced composite(FRC) applications [8]. UHMWPE is synthesized by using the ethylene monomers that are bonded together to form the long linear chain. When

UHMWPE in the drawn state, it is the crystalline polymer with a wide range of applications. The initial use of UHMWPE was in the bulk form and included prosthetics for biomedical arthroplastic procedures. In late

1970s, UHMWPE fibers were commercialized by the Dutch chemical company DSM under the trade name

Dyneema®, and lead the wide range creation of high performance fabrics for usage in sails, ropes and in long-fiber reinforced composite laminates that used in ballistic and blast armors. In early characterization on UHMWPE fibers, creep response, time-temperature correspondence and mechanical properties were studied when applied in fabricating laminates, all those effort was for the aim of clarifying the potential of such composites for structural applications [9]. UHMWPE fibers have been widely used in ballistic armor and ropes because they have the properties such as the high strength, high modulus, high impact resistance, high cut and abrasion tolerance, excellent chemical resistance, low moisture absorption and low density, low dielectric constant, etc., however, they have the disadvantages that sensitive to creep under the increasing temperature or long term loading [6][10]. Long term exposure will cause PE to exhibit oxidative chain degradation, hydroperoxides are formed during oxidative degradation and finally they decompose and carbonyl compounds are formed. Also, long term exposure lead the decrease of mechanical properties.

Various methods, such as the Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), nuclear magnetic resonance spectroscopy (NMR), were used to characterize the chemical and physical structure of UHMWPE fibers [10].

2.1.2 Production

Organic monomer (CH2=CH2) is the repeat unit in ultra-high molecular weight polyethylene molecular chains, organometallic catalysts developed by Ziegler and others were used as initiators in suspension polymerization to manufacture linear molecular chains and high molecular weight [11].

UHMWPE can also be named as high performance polyethylene, which is produced by using gel spinning to get high degree of molecular chain orientation (greater than 95%) and high crystallinity (higher than

85%). The gel-spinning process includes three basic transformations: (1) polymer to gel, UHMWPE polymer was dispersed with non-volatile solvent; (2) gel to Xerogel, the solvent removed or partially removed by using a volatile solvent and increasing temperature; (3) extension and orientation drawing, in this stage the remaining solvent removed and high performance polyethylene fibers are produced with certain draw ratio named as superdrawing, the final properties of the fiber are achieved in this stage. Figure

2 shows the schematic of the gel-spinning process. Normally the attainable draw ratio increases with decrease in concentration. It is established that there is a minimum concentration for each molecular weight as concentration lower than the minimum can lead to insufficient molecular overlap which significantly reduce the final performance properties of UHMWPE fibers [7][11].

Figure 2 Gel-spinning process schematic [11]

UHMPE polymer chains have weak Van der Waals intermolecular bonds and the stress transfers through the chain overlap. Therefore, high molecular weight with high chain extension and sufficient chain overlap are needed to create sufficient intermolecular interaction which leads to the high performance properties

[11].

Figure 3 shows that UHMWPE fibers consist of macro fibrils of infinite length along the fiber direction, the macro-fibrils consist of microfibrils with smaller diameter. The micro-fibrils are composed of crystal blocks and disordered domains. The disordered domains consist of chain ends, chain entanglements, and taut tie molecules (TTM) and other imperfections, they all can be considered as the weakest spot in the microfibrils. Tensile strength in these imperfections is believed to be transferred by the TTM and entangled chains. The ratio of disordered domain length to crystal block length is thought to determine the elongation at break and the tensile modulus [12].

Figure 3 Schematic illustration of UHMWPE fiber's structural hierarchy [13]

Schaper’s study indicate that the structure of the microfibril is not uniform in density and this uniformity in density could produce domains that containing a high concentration of crystal defects. The PE crystals have the capacity to undergo solid state transformations without breakage of primary bonds, and this ability is an important factor in the performance of damage tolerance of UHMWPE fibers. Also, the analyses of

X-ray diffraction patterns from strained samples indicates that the PE crystals are covalently bonded to the surrounding rubbery matrix play an important role in the damage tolerance and impact resistance of composite materials reinforced by UHMWPE fibers [14].

2.1.3 Fiber Properties

Also, Figure 4 shows the higher crystallinity of UHMWPE fiber will give higher strength and modulus.

[15] According to previous studies, the fracture process of UHMWPE fibers is mainly controlled by many factors such as chain scission or intermolecular chain slippage, which belong to the molecular events [16].

(a) Breaking strength vs. crystallinity

(b) Initial modulus vs. crystallinity

Figure 4 UHMWPE fiber tensile property vs. crystallinity. (a) Breaking strength vs. crystallinity; (b)

initial modulus vs. crystallinity [15]

UHMWPE fibers have the volume density as low as 0.97 g/cm3 which makes these fibers have extremely high specific strength or tenacity and specific modulus as they already have very high strength and modulus.

Figure 5 shows UHMWPE fiber and other fibers comparison of strength based on weight to strength based

10 on volume. High specific strength and specific modulus also indicate UHMWPE fibers are the choice of weight saving and volume saving for fabric or composite applications [7].

Figure 5 Strength based on weight vs strength based on volume of various fibers. [7]

UHMWPE fiber’s ability of absorbing extremely high amount of energy can be utilized in product for ballistic protection, cut resistance gloves and motor helmets. The impact strength of carbon or glass fiber reinforced composites can also be improved by using these fibers [7]. Also, UHMWPE fibers have very good performance in fatigue and abrasion properties. Spectra® fibers not only have high modulus but also high flexibility and long flex life which related to its relatively low compressive yield stress, which is 0.05

GPa. Figure 6 shows the abrasion and flex life of various fibers.

Figure 6 Abrasion and flex life of various fibers. [7]

UHMWPE fibers have a very low porosity which leads these fibers have very low or no water absorption.

As UHMWPE fibers have no aromatic rings or any amid, hydroxylic or the chemical groups that can be attacked by aggressive agents. They have very good resistance and can be unaffected by lots of acids and alkalis, UHMWPE fibers can be stable for many years in normal air even they are sensitive to oxidation media. Figure 7 shows UHMWPE fibers have relatively good resistance to ultraviolet (UV) light but the resistance ability is limited when they are exposed to UV light continuously or for a long time.

Figure 7 UV resistance of high performance fibers. [7]

Despite the impressive list of properties, UHMWPE fibers have limitations in applications, for instance, their polymeric structure characterize them with chemical inertness and lack of functional groups which lead the poor bonding ability with most materials. This characteristic make it difficult to produce UHMWPE fiber reinforced composite with expected strength. In other words, the poor interfacial adhesion between the UHMWPE fibers and polymer matrix lead to obtain a composite material with weak properties, and the usage of UHMWPE fiber in composite materials are limited if no surface treatments conducted.

As the fiber surface modification is necessary, many fiber pretreatment methods are developed to improve the interfacial bonding strength, for instance, plasma treatments, chemical etching and UV-initiated graft copolymerization [17]. Oxygen-plasma treatment of UHMWPE fiber can improve the transverse properties of UHMWPE fiber/vinyl ester composites, the interfacial adhesion between the UHMWPE fiber and vinyl ester can be improved due to the introduction of micro-pits, which creates a mechanical interlocking between the fiber and resin [18].

Despite those surface modification methods, UHMWPE/Carbon hybrid fiber can also be produced to increase the bonding strength between the fiber and matrix [19]. HDPE can be used as the polymeric matrix

13 for fiber reinforced composites, and self-reinforced PE-PE composites can be produced because the chemical identity of UHMWPE and HDPE make them perfectly suitable to produce self-reinforced composite material [20].

The tensile properties of the untreated UHMWPE fibers were found to be dependent on both gauge length and crosshead speed, breaking load and tensile modulus decrease as the crosshead speed increases [12].

Another study conducted the tensile impact tests on UHMWPE fiber bundles at two strain rate and two temperatures. Experimental results indicate that the mechanical properties of UHMWPE fiber bundles can be affected by the strain rate and temperature. The increase of temperature will significantly decrease the initial Young’s modulus of the fiber bundle, the strain decrease with the increased strain rate and increase with increased temperature [21].

2.2 TLCP fiber-Vectran® HT fibers

2.2.1 Introduction

The liquid crystal polymer (LCP) fiber is wholly aromatic polyester that is produced by the polycondensation of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid. Since 1986,

Hoechst Celanese and the Kuraray Company Ltd of Japan have jointly evaluated Vectran® fiber in various applications [22]. LCP fibers belong to the category of the rigid or rod like liquid crystal polymers whose main characteristic is that the rigid rod-like chain segments form an ordered phase, and in this phase the molecule segments show unidirectional order which is stable in a certain temperature range [23].

Thermotropic Liquid crystal polymer (TLCP) fibers are used as the reinforcement in the composites when the composite materials need the characteristics of unique property and performance that can be provided by them. For instances, TLCP fiber has excellent performance in damping that make them useful and efficiently applied in the applications such as bicycle forks, hockey sticks and tennis racket handles. TLCP fibers are the fibers with high strength, low moisture absorption and superior abrasion resistance and are used to make rope, fishing nets, sheeting and many other products. TLCP fibers are also applied in non- implant medical applications such as catheters and surgical device control cables, both of the good

14 performance of withstand gamma ray radiation and very low deniers make TLCP fibers are suitable for these applications [24]. Generally, TLCP have mainly been developed in industry and their commercial applications are based on their mechanical properties as well as their thermal and solvent resistance. The literature on polyarylates is very extensive and generally focused on understanding molecular parameters and optimizing processing conditions in order to get the most profit from their unique characteristics such as low shear viscosity and low die swell [23][25].

2.2.2 Production

Vectran® fibers are thermotropic liquid crystal polymers (TLCP) which is produced from Vectra LCP polymer. The polymer is produced by using p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic in the acetylation polymerization [7]. These fibers have many characteristics such as excellent mechanical properties, strength retention over a wide range of temperatures, excellent chemical resistance and low moisture absorption as mentioned above. Unlike the UHMWPE fiber, Vectran® fiber is thermotropic and produced from melt-spun which indicate the fibers does not induce the decomposition at certain high temperature. However, the liquid crystal polymers are highly oriented in the fibers to achieve high tensile properties. The molecules of the liquid crystal polymer are rigid that they can position themselves into randomly oriented domains. The term ‘liquid crystal polymer came from the polymer’s special anisotropic behavior in the melt state. By extruding the molten liquid crystal polymer through small spinnerette holes, the molecules can be highly oriented and parallel to each other along the fiber direction that lead the produced fibers have high molecular orientation and high tensile properties. The Figure 8 shows the schematic diagram of the liquid crystal polymer chain structure before and after the melt spinning. High strength TLCP fibers are achieved by heat treating in an inert atmosphere and lubricant is used to benefit the fiber manufacturing process. The water should be removed before the final heat treatment as the residual water can affect the inert atmosphere and prevent TLCP fibers from achieving maximum physical properties.

Figure 8 Schematic diagram of the liquid crystal polymer chain structure [22]

2.2.3 Fiber properties

Properties such as high strength and modulus with low elongation are very important for most TLCP fibers in the market [7].

Creep is an important property for high performance fibers, especially in certain rope applications. Martin

Marietta Company conducted a creep tests on Vectran® braid by applying the load as 37% of the rated breaking load of the braid, and the experimental results indicated that no creep growth was observed after

180 days [22].

Whitehill manufacturing Corporation conducted the stress-relaxation test on a wire rope construction made from Vectran® fibers. A fixed load was applied to give the tension to the test sample, and the tensions were periodically recorded from the load cells at the end of each sample. The load decreases if the creep occurred, and the load will be tensioned back to the original load [22]. Figure 9 Creep tests were conducted at ambient temperature show the Vectran fibers exhibit no creep when loaded at 50% of the breaking strength.

Figure 9 TLCP parallel strand rope stress relaxation. Whitehill Manufacturing Corporation

WMCJETS/JETSTRAN 1-A VEC ½” Rope. [7]

Highly oriented fiber structures contribute the high strength and modulus to TLCP fibers. As mentioned above, TLCP fibers are rigid rod like fibers and the flex fold testing failures were generally observed from the strain localization, kink band formation or fibrillation. Kind band formation can absorb more energy to increase flex cycles and this kind band is believed to be formed from the fibril dislocations caused by buckling and break of the stiff polymer chains. Figure 10 shows the tensile strength retention of Vectran fibers after flex cycles.

Figure 10 Tensile strength vs flexural fatigue of Vectran HS and aramids. [7]

Vectran® fibers with no finishing treatment had low abrasion-resistance, however, the Vectran® fiber’s abrasion resistance can be significantly improved by applying small amount of processing lubricant. Also,

Vectran® fibers have good fatigue resistance, a fatigue resistance study was conducted by Martin Marietta to make a comparison between the Vectran® braid and Kevlar® braid and the result indicated that the strength of Vectran® braid was reduced only by 10% when compared that of Kevlar® braid, which the strength was reduced by 30% [22].

For strength retention, Vectran® fibers have different heat resistance behavior in different situations. When the Vectran® fiber was exposed to a temperature range of 25℃-250℃ for 24 hours, after the exposure, the temperature was recovered to environmental temperature. The results indicate that the Vectran fiber have better strength retention when compared with Kevlar® fiber. However, when the tensile strength was measured at elevated temperatures, the results indicate that the Vectran® fiber didn’t retain the strength as well as Kevlar® fiber. Figure 11 shows the different heat resistance behavior of Vectran® fiber.

(a) (b)

Figure 11 Comparison of tenacity retention of Vectran HS and Kevlar 29 in different situation. (a)

Tenacity retention after thermal exposure; (b) Comparison of tenacity of Vectran® HS and Kevlar® 29 at

elevated temperatures [22]

Chemical resistance is another excellent characteristic of Vectran® fiber, the Table 1 shows that the

Vectran® fiber can have a good strength retention after exposure in many selected chemicals.

Table 1 Strength retention of Vectran® HS fiber after chemical exposure [22]

Concentration Temperature Time Strength Chemical (%) (ºC) (days) retention (%) Acetone 100 20 1 95 Nitric acid 70 20 1 76 20 1 99 Hydrochloric acid (pH=1) 70 7 95 Perchloroethylene 100 20 1 92 Sodium 20 1 100 (pH=13) hydroxide 70 7 91 Sulphuric acid 10 20 1 93

All these properties mentioned above make the Vectran® fiber to be a good option in material selection in some specific applications, particularly in applications in which other fibers’ properties are not perfectly satisfied with the performance requirement.

Vectran® fibers are currently widely applied in many different areas such as high altitude balloons for ultra- long duration that requires the use of high strength fibers [26]. The airbags on Mars Pathfinder were using the Vectran® fibers, four layers of Vectran® stitched at the bladder seams [27]. In 2008, the new Zoom

Victory Spike running shoes from Nike were using the Vectran® fiber that supplied from Kuraray. These

Vectran® fibers were converted into embroidery thread that is new Flywire technology, and 116 Vectran® fiber Flywire strands were applied on each shoe to provide support and cushioning at key points such as the forefoot and heel [28]. Also, Vectran® fibers can be applied to build shielding system to protect the

International Space Station from space debris. The experiment result indicates that the deployable single bumper shielding system applied Vectran® can be produced with light weight, flexibility and less thickness which is approximately one sixteenth compared with the mesh stuffed Whipple bumper shield installed on the Japanese Experiment Module, and the areal density of the bumper made with Vectran® is half to this installed bumper [29].

2.3 PBO fibers-Zylon® HM fibers

2.3.1 Introduction

PBO, poly(p-phenylene-2,6-benzobisoxazole), fiber which is under the trade name Zylon® was commercialized by Toyobo Co. in 1998 after about 20 years of research in the United States and Japan.

PBO fibers are commonly known as high performance rigid rod isotropic crystal polymer fibers [11]. When compared to other commercially available high performance fibers, PBO fibers have outstanding tensile properties such as the tensile strength of PBO fibers is 9 times that of steel, also the specific modulus of

PBO fiber is 9.4 times that of steel. And PBO fiber reinforced composite materials have attracted much interest in the fields of research and industry [30]. However, PBO fibers have very poor resistance to the

UV light and their tensile strength will decrease in hot and humid environments. PBO fibers have great thermal stability and exhibit no softening behavior prior to thermal degradation temperature at 650°C [11]

[31].

2.3.2 Fiber production

During the PBO fiber production, monomer 4, 6-diamino-1, 3-benzenediol dihydrochloride (DABDO) and monomer terephthalic acid (TA) or its derivative are used as the polymerization precursor. Polyphosphoric acid (PPA) plays a complex role in the PBO fiber polymerization, PPA has the function of solvent, catalyst and dehydrating agent in the polymerization. PBO shows lyotropic property and displays liquid crystalline behavior, this ability is related to its concentration in solution. As a lyotropic liquid crystalline polymer,

PBO polymer has high thermal stability and degrades at the temperature before it melt. Dry-jet wet spinning technique is used to spin PBO fiber directly from PPA solution of polymerization. During the manufacturing process, fibers formed from the spinneret arrive the coagulation bath after traveling through the air-gap, then PBO fibers get post processing treatment such as washing, drying and heat-treated under tension [11]. Figure 12 shows the simplified schematic of PBO polymerization.

Figure 12 Simplified schematic of PBO polymerization. [7]

Microfibril structure includes the amorphous and disordered regions of crystalline and it is a common feature of high performance polymer fibers, some models are used to describe the fiber structure. Figure 13 shows the PBO fiber structure model, from the model, the microfibrils which consists of highly oriented

PBO fiber molecules that lay parallel to the fiber axis. There also have void between the microfibrils that also indicated by this model [7].

Figure 13 PBO fiber structure model [7]

2.3.3 Fiber properties

The reported PBO fibers can have tensile strength and modulus as high as 5.8 and 352 GPa respectively.

Also PBO fibers have good cut resistance as the energy needed to cut Zylon® fibers at an angle of 90º was

4.5 and 3.2 times greater than the energy needed to cut Kevlar® and Spectra® fibers respectively. PBO fibers are sensitive to the increasing temperature and humid environment, their tensile strength deteriorate sharply under UV exposure and visible light exposure in long time. PBO fibers have lower abrasion resistance than UHMWPE fibers and fiber’s compressive strength is as low as 0.2 to 0.3 GPa which restrict their use in composite materials. The thermal decomposition temperature in air is about 650ºC for PBO

22 fibers and they have the highest limiting oxygen index (LOI) among the polymeric fibers indicates their relatively low combustion ability [7][11].

Figure 14 shows the specific strength vs. specific modulus for various fibers and it indicate that PBO fibers relatively high specific stress and specific modulus when compared to other high performance fibers.

Figure 14 Specific strength vs. specific modulus for various fibers. [7]

Figure 15 indicates that PBO fiber tensile strength is slightly dependent on the gauge length, tensile strength decreases sharply before the gauge length exceed 3 inches, after the gauge length is high than 3 inches, the tensile strength trends to be even and decrease very little bit. Such trend, which is the characteristic of high modulus, brittle materials, can be explained by the critical flaw concept. For long gauge length fiber, there exists a higher possibility of critical flaws or defects on the fiber surfaces that can lead the fracture of the fiber. However, the modulus of PBO fiber seems to be constant for all gauge lengths that indicates the strength reduction was caused by the premature failure at lower strains [32].

Figure 15 Tensile strength dependence on gage length for cis-PBO fibers (0.02/min strain rate and

twists/in.) [32]

Certain level twisting can improve the tensile strength and modulus of PBO fibers at certain level as twist can help reduce the effect of prematurely damages. Figure 16 shows the tensile strength and modulus variation with the number of twists per inch applied to the PBO strand. The results indicated that the improved tensile strength without decreasing the modulus was achieved by 6 or 7 twists per inch for the given strand size. However, excessive twisting decreases both the tensile strength and modulus. These reductions can be explained by either the increased spiral angle which lead the fiber easily break across the axil direction, or the fiber surface damage that lead the early fracture behavior on the fibers [32].

Figure 16 Dependence of tensile strength and modulus on twists/in for 130 denier cis-PBO fiber bundles.

(0.02/min. strain rate and 5 inch gauge) [32]

In a study, fatigue tests were conducted on PBO single filaments and the results indicate that PBO fiber fracture failure involves splitting and fibrillation. The test were conducted with two level of loads that include 60% of the mean measured tensile breaking load and cyclic 0-70% of the mean measured tensile breaking load. Figure 17 shows the PBO fiber can support much higher cyclic stresses than other fibers

[21][ 33].

Figure 17 Comparison of PBO cyclic behavior with polyester, aramid and HMPE in terms of applied

stress [33]

PBO fibers have very low resistance to UV degradation damage and humidity corrosion as mentioned above. In 2009, a bullet proof vests manufacturer, First Choice Armor & Equipment Inc., was sued by the

United States for false claims of bullet proof vests made with Zylon® fiber. The Zylon® fibers have problems in manufacturing and degradation which lead the material made by them be unsafe for ballistic use [34]. The poor resistance to UV-Vis damaging limit their usage in many applications, however, PBO fibers possess the relatively high strength and modulus when compared with other commercialized high performance fibers, the fiber additional treatments are needed to make this superior fiber available for high altitude and aerospace applications, the methods including the surface modification, coating with UV blocker or absorber, gamma-ray irradiation, etc. The adding of UV blocker or absorber and surface treatment may lead the decrease of the fiber strength [30][33][35]. Also, the surface treatments are needed to improve the interfacial strength between the PBO fibers and the matrix because the interfacial adhesion between fiber and matrix in a composite system is an important factor for the stress transfer from the matrix to fiber components. The surface treatments include the chemical treatment, plasma treatment, electrolytic oxidation and coupling agents, etc. [36]. The Figure 18 shows the SEM micrograph of the untreated AS type PBO fiber with the smooth surface that has poor interfacial adhesion ability.

Figure 18 SEM micrograph of the untreated AS type PBO fiber [36]

For composite reinforcement, composite reinforced by PBO fibers are limited to be used as secondary structures and non-structural applications as fibers have poor compressive strength mentioned above. PBO fibers can provide excellent mechanical properties to secondary structures in wide fields such as athletic equipment and high-fidelity speaker cones. For non-structural applications, PBO fibers are normally in the form of woven fabrics and cables to give the benefits to the structures with improved comfort and mobility, such as the heat and flame resistant work-suit for firefighters and the protective area (knee and elbow) of motorcycle suits.

2.4 E-glass fibers

2.4.1 Introduction

The production of glass into fine filament can be dated as early as even before the technology of glass blowing [7]. Glass fibers are the isotropic material that they have the same Young’s modulus and coefficient of thermal expansion along the fiber axis and perpendicular to fiber axis. These glass fibers have relatively low density when compared with metals, however their Young’s modulus is not so high which is only moderate. Commercially available glass fibers can be produced into forms of strands, chopped strands, woven roving or woven cloth. Resins, rubbers or polymers are often used matrix that E-glass fiber can be ember into to provide durable structural composites with a wide range of application. Also, glass fibers are used in a number of applications include insulations, filtration media, reinforcement and optical fibers [7,

37]. As lots of researches have been conducted on E-glass, the properties of them have been thoroughly studied which leads the well-established knowledge that E-glass fibers are much stronger than the corresponding glass in bulk formation, however, these fibers will lose their high strength after aging and E- glass is not resistance to acid or alkalis [38].

2.4.2 Fiber production

Nowadays, more than 99% of continuous glass fibers are spun from an E-glass formulation and E-glass fiber is most frequently used because it has good chemical resistance, wide availability, good mechanical properties and relatively low cost. E-glass is an alumino-borosilicate glass with low alkali content which is calculated as Na2O (<1 wt%) [7][38]. Table 2 shows the typical range of formulations for E-glass fiber.

Table 2 Typical fiber-forming E-glass compositions [7]

Glass fiber manufacturing process has effectively two methods: (1) glass marbles preparation followed by remelt process and fiberisation stage; (2) direction melting route which the melting glass is continuously extruded through nozzles under gravity. Direct melt spinning is more predictable rather than the method of remelting preformed marbles which introducing the complexities. Figure 19 shows the schematic process of direct melt production process for glass fiber filaments [7]. The glass raw materials were mixed and transported into the melting furnace and the glass fiber filaments are produced through the nozzles by its gravity. Then the bushing filaments are formed and the fibers are immediately cooled by sprayed water, coated with sizing agent and then assembled into a strand and wound into rovings. The sizing and finishes are immediately followed by the cooling with water, aqueous sizing agent which is usually an emulsion is applied on the fiber by contacting with a rubber roller. The size or finish process is critical to glass fibers’ handle ability and compatibility with the matrix. Also, other finishing agents are used in this process such as the lubricants, surfactants, antistatic agents, etc.

Figure 19 Schematic of direct melt process for production of continuous filament. [7]

2.4.3 Fiber properties

For tensile property, E-glass fiber has the stress-strain curves that they remained linear between the stress and strain until failure which indicates the simple Hookean stress-strain curves, in other words, the tensile strength is proportional to the strain. The fiber strength critically depends on the state of the fiber surface while partly depends on the inherent structure. Figure 14 indicates that tensile performance of E-glass fibers is in the lower bracket of high performance fibers.

Usually, the surface of E-glass fibers is smooth under the scanning electron microscope. And the tensile fracture morphology for all the glass fibers tested was the classical brittle facture which indicated by the

Figure 20 [39].

Figure 20 SEM images of some E-glass fiber fracture surfaces. [39]

These brittle fracture is in correlation with the Hookean stress-strain curves which indicates that the glass fiber broken without plastic yield. When tension achieved to a certain level, the failure is usually initated from the surface flaws and the deepest crack starts to propagate radially until it exceeds the local tensile strength of the glass fiber which leads to the catastrophic failure. Breaks perpendicular to the fiber axis which is the simplest form are frequently observed.

2.5 Single fiber tensile properties

As fibers are the load carrying component in a fiber reinforced composite material, their tensile properties play an important role in decision of applications that they can be applied. High performance fibers are widely applied in modern composite materials and their tensile strength and tensile fracture behavior have been studied by many researches. The Figure 21 shows the typical stress-strain curves for many different polymeric high performance fibers.

Also, the stress-strain curves indicate that PBO fibers, Vectran® fibers have the stress almost linearly proportional to the strain until failure. The Spectra® fiber and Dyneema® fiber which are both UHMWPE fibers have the clear slope decrease as the deformation proceeds close to breaking strength, indicates a non- linear curve. According to a study, the experiment results clearly indicate that the high performance fiber

PBO (Zylon® HM) has the lowest Weibull modulus and failure strain. The difference in the stress-strain curves among high performance polymeric fibers can be explained by the difference in the crystallinity and preferential orientation of the fibril structures, and the molecular structure and molecular weights can also have the effect on the absolute tensile modulus and strength of the high performance fibers [40].

Figure 21. Typical tensile stress-strain curves for the PBO, PPTA, PPODTA, PAR, PE and PLA high performance polymeric fibers. (a) PBO fibers, (b)PPTA fibers, (c)PPODTA fibers, (d)PAR fibers, (e)PE

fibers, and (f)PLA fibers. [40]

2.6 Tensile property relationship between the single fiber and yarn

Based on the rupture strength of chemical bonds and the strength of components, the theoretical strength of any material have been never achieved, as the presence of flaws that lead to localization of stress in excess of theoretical strength [41]. As the test gauge length of the specimen increase, the strength of a material decrease due to the presence of a distribution of flaws of wide ranging magnitude, in other words, long gauge length increase the possibility of flaw or defect localized in the gauge length. Peirce proposed the

“chain weak theory” and many analysis models have been improved based on this theory. And those analysis models are widely applied to estimate the single fiber tensile strength.

Textile engineers always have been interest in the relationship between the break strength of a bundle of fiber and that of a constituent fiber. When the bundle of fibers is applied with a tensile load, the fiber with lowest strength will break first and the load is then transferred to the remaining fibers. Some researchers found from the load-elongation diagram of a multifilament yarn that the yarn breaks in stages as the filaments in a yarn can never be absolutely identical in mechanical properties. Therefore, in an extreme case, if each filament significantly differs in elongation-to-break from all the others, the obvious breaking stages of the yarn can be observed and the number of the stages should be as same as the number of the filaments in the yarn. As most of fibers or filaments’ tensile strength obey the Hooke’s law, which means filament with lower breaking load have lower elongation while the filaments with higher breaking load have higher elongation. Thus, the weaker filaments will break earlier than the strong filaments. When the filament breaks, the load on that filament is lost and there is a drop in total load on the yarn which indicates the stages of the yarn breakage. Figure 22 shows the relationship between the total breaking load and the number of filaments in the yarn. Based on Figure 22, in some extent, the increased number of filament in a yarn will not give the same load value increase to the yarn.

Figure 22 Distribution of filaments according to their TBALF (tenacity based on average load on

filaments) [42]

2.7 3D woven composites

For composite materials, low mass with combined excellent stiffness and strength is the most notably desired properties. In traditional 2D composites, they have excellent in-plane tensile strength and many different processing methods. However, due to the lack of through thickness reinforcement, traditional 2D composite materials are prone to delamination, also the production of 2D composite materials require expensive, labor intensive manufacturing procedures. 3D woven composite materials are a new type of advanced engineering material that is currently used in only a few applications [43]. Applications such as the stiffeners for the air induct duct panels on the Joint Strike Fighter, aircraft wing joints on the Beech

Starship and rocket nose cones are the most significantly important applications. 3D woven composite materials are also used in many applications such as the floor panels for trains, hard-tops for convertible cars and the deck and top-side structure for a fishing boat. The present use of 3D woven composite materials are limited by the cost of product processing which is currently higher than 2D prepreg or fabric laminates

34 for many applications. However, the future of 3D woven composite materials is promising and the potential use is very impressive and wide ranging with many different possible applications in the aerospace, marine, infrastructure, military and medical fields. The 3D woven composite materials are still not fully understood and accepted by the composites industry is another important challenge.

2.7.1 3D woven preforms

3D woven fabrics can be achieved by traditional 2D weaving loom or 3D weaving machine. The Figure 23 shows the classification of 3D woven fabrics based on weaving technique. [44]

Figure 23 Classification of 3D fabrics based on weaving technique [45]

The 3D fabrics including through thickness angle interlock and layer to layer angle interlock were developed and used in many composite applications. Mohamed and Zhang patented a weaving method to produce the 3D woven fabric that called 3D orthogonal woven fabric. In this type of 3D woven fabric, there has no interlacing between the warp yarns and weft yarns, they are and perpendicular to each other. And the z-yarns combine the warp layers and weft layers by interlacing through thickness along the warp direction over the weft yarns. The orthogonal structure in this type of 3D woven fabric reduce the crimp of warp yarns and weft yarns that benefit the maximum load carrying ability of high performance fiber

35 reinforced composites. Figure 24 shows the schematic diagram of 3D orthogonal woven preform with plain weave for 4 layers.

Figure 24 Architecture of 3D orthogonal woven fabric with plain weave and 4 layers [44]

The fiber architecture to the woven preform and weaving process have significant effect on the microstructure of a 3D woven composite material, the consolidation process have very limited effect on the

3D woven composite materials’ microstructure. During the processing of 3D woven composites, various types of microstructure defects might be produced and the defects can degrade the in-plane, out-of-plane and impact properties. Abrasion and breakage of the warp, weft and z-yarns are common type of damage incurred in 3D weaving that are difficult to avoid. This damage occurs by the bending of yarns in the weaving process and as yarns slide against the loom parts (guides, heddle eyes, reed wires). Figure 25 shows the broken filaments in a yarn that passing through a guide in a 3D weaving machine.

Figure 25 Broken filaments passing through the guide [46]

Figure 26 shows the cumulative probability distribution plots of yarn tensile strength. The yarn tensile strength reduced after each manufacturing process compared to as-received yarn due to different stresses the yarn encountered during each process [46].

Figure 26 Cumulative probability distribution plots of the tensile strength of a 300 tex E-glass yarn

determined after different stages of the 3D weaving process. The average tensile strength value of the

yarn after each weaving stage is shown. [46]

Except the abrasion and fracture happened to the yarns during the 3D weaving, the fibers in 3D woven interlacing preforms have higher distortion and crimp when compared with 2D prepreg laminates.

2.7.2 Resin matrix

As mentioned earlier, fibers are the key role in determining the stiffness and strength of a composite material, the choice of matrix materials can decide the service temperature, viable processing approaches and long term durability of fiber reinforced composites. Polymer matrix are widely applied in producing advanced high performance composites, they can be divided into two categories: thermoplastic and thermosetting.

Thermoplastic polymers have been known for a long time, recently, conventional thermoplastic polymers had flexible carbon chains that can be easily extended and rotated into different configurations. These polymers have many limitations such as low elastic modulus, low glass transition temperature (Tg) and poor solvent resistance. Recently, high performance thermoplastics have been introduced to surmount these limitations and some of them can compete with the best thermosets [47].

Unlike thermoplastic polymers, thermosetting polymers are not soften on heating and stiffen on cooling repeatedly. 3D network structure can be formed during the curing process which make the polymers are infusible and insoluble materials. 3D network structures can be named as 3D crosslinked networks which are molecular based networks depending entirely on covalent bonding and macromolecular interactions or entanglement of long polymer chains. Crosslinking network are formed during chemical reactions that driven by heat generated either by the exothermic heat of reaction or externally supplied heat which normally applied to shorten the curing time. Thermosetting polymer curing process have gelation point that the curing reactions accelerate to reduce the available volume within the molecules, the resin viscosity increased and a rubbery solid can be formed. The polymer cannot be remelted after the gelation. Figure 27 shows the comparison of thermoset and thermoplastic polymer structures [48].

Figure 27 Comparison of thermoset and thermoplastic polymer structures. [48]

Typical fiber reinforced composite fabrication processes include hand-layup, pultrusion of reinforcing strips and secondary bonding, filament winding and vacuum assisted resin transfer molding. Vacuum assisted resin transfer molding (VARTM) has been a widely used method to fabricate structural composites and composite fabrication in labs as it is cost effective. However, VARTM is conducted under low pressure which lead to a reduced fiber volume fraction with lower composite properties than that of composites produced by autoclave. Also, strict control of geometry in VARTM is not yet possible due to it is one-side tooling process [49]. Figure 28 shows the side view of VARTM process and thickness difference during the resin infusion.

Figure 28 Effect of fluid pressure on compaction in vacuum infusion. [50]

2.7.3 3D composite mechanical properties

After decades’ research and development, the specific strength and moduli of fibers and matrix materials have reached the limits, better understand on how fabric architectures affect and control the mechanical behavior of high performance fiber reinforced composites is needed. So the better fiber geometrical arrangement can be developed and utilized for specific fields as any composite properties are greatly affected by the fiber geometrical arrangement inside the matrix and the interfacial interaction between the fiber and matrix [51]. When the composites applied in structure components, filament yarns must be multi- directionally positioned to meet the criteria of construction part. For composites reinforced with 3D woven preforms, they have the ability to meet structural component load bearing criteria with minimized interlamination and improved fiber volume fraction. When compared with traditional composite laminates,

3D woven composites also have good resistance to the transverse impact, especially in aerospace, military, civil engineering and automobile industries where low speed impact is the normal form of loading [51][52].

A low speed impact experiment was conducted by Seltzer et al. and the experimental results indicate that for both carbon fiber and fiber glass applied as reinforcement, 3D woven composites had specific energy absorbed (energy normalized by areal weight) as high as twice that of 2D woven laminates [53].

As mentioned above, 3D woven preforms can be produced by using the existing 2D weaving system, Behera et al. conducted a composite mechanical properties related on 3D woven preform reinforced composites and 2D woven composites and 3D woven preforms were produced by the 2D weaving system. E-glass fiber was used in this research. Figure 29 shows the experimental results of the tensile property for these composites.

Figure 29 Load elongation curve of different structures. [51]

From Figure 29, 3D orthogonal woven composites have much better performance of tensile strength in weft wise direction when compared with the warp wise direction. However, delamination was observed on 2D woven composite during the test. Also, the low speed impact test was conducted and Figure 30 shows the results. From Figure 30, 3D structures, especially orthogonal structure, definitely show better impact resistance when compared with 2D plain woven composites and this results indicate 3D structures have more suitability for impact resistance applications. Also, due to the interlaminar toughing mechanisms includes de-bonding, fracture, pull out and the crack bridging from z-direction yarns can impede the delamination from impact area [47].

Figure 30 Bar diagram for impact properties of different structures. [51]

However, the author didn’t show the normalized tensile strength with fiber densities and the normalized impact properties with areal density. The normalized tensile strength and normalized impact property can give a much more accurate assessment of the comparisons between 3D structures and 2D structures.

Despite the fiber reinforcement geometrical arrangements have effect on the final composite mechanical properties, the interfacial interaction between the fiber and matrix also contribute to the composite mechanical performance. As mentioned above, fiber is the major load carrier and there has the load transfer theory which the load applied to the resin transfer to the fibers. To increase the interfacial interaction, surface treatment is often used on the fiber by different methods that needed in different situations. After the fiber surface treatment, interfacial interaction can be divided into 5 types which include micromechanical interlocking, permanent or induced dipole interactions, chemical bonding, chain entanglement and transcrystallinity. Figure 31 shows the schematic graphs for different types of interfacial interactions between fibers and matrix.

and (e) transcrystallinity [49]

Resin selection also have effect on the mechanical properties of the final composite materials, and usually thermoset and thermoplastic resin are used as the matrix in the composites. Force-deflection curves can give the information about the impact test and the specimen. The impact test result can be divided into three categories which include rebounding, penetration and perforation. Normally, the impact tests resulted as rebounding can be indicated by the closed force-deflection curves while the open curves indicate the impact tests resulted as penetration or perforation situation. The absorbed energy can be determined from the covered area under the force-deflection curve. Figure 32 shows the fiber glass reinforced composite by using thermoplastic resin and thermoset resin after the repeated impact test.

Figure 32 Section view of the specimens after 50 J repeated impact test [54]

From the Figure 32, thermoset composite had a local deformation and delamination in a small area which indicate the damage propagated through the thickness. Unlike the composite with thermoset resin, the damage such as the delamination and matrix deformation in thermoplastic composite was involving the entire specimen body while only fibers were observed broken in local area.

Keiji Ogi et al. (2009) conducted a high speed impact damage behavior in a 3D woven SiC/SiC composite and the impact damage was introduced by the projection of a steel ball. Previous research on the impact damage behavior of 2D CMCs was studied and compared with the impact damage behavior of 3D CMCs.

The results indicated that cone cracks were observed in both 3D woven CMCs and 2D CMCs with or without perforation. However, 2D CMCs had multiple cone cracks accompanied with delamination while

3D CMCs had no delamination observed. The perforation damage or spall fracture happened when applied impact energy exceeding the critical energy. Keiji Ogi et al. also concluded that z-yarns in the 3D CMC have the importance in improving impact resistance [56]. Figure 33 shows the schematic illustration of foreign objective damage for both 3D CMCs and 2D CMCs with or without perforation.

Figure 33 Schematic illustrations of foreign object damage in (a) the 3D CMC without spall, (b) the 3D

CMC with spall, (d) the 2D CMC without perforation and (e) the 2D CMC with perforation and plain

views of (c) the 3D CMC and (f) the 2D CMC [56]

3. Objective

In fiber reinforced composite materials, fiber is the major load carrying element in FRCs while the resin matrix protect fiber from environmental damages. Fiber glass and carbon fibers are widely applied in most related composite material researches, and the lack of comparison between different types of high performance fibers motivates the conduction of this research.

Previous work focused on the effect of fabric architecture on the mechanical properties of final composite materials, such as the weft yarn density, different weave designs, and different number of layers. The role of fiber type in determining the final composite performance has been limited to glass and carbon fiber.

Most of the research dealt with 3D composite from stack of 2D preforms. To our knowledge, the fiber type role in the performance of their composites from 3D orthogonal woven preforms has not been researched for the range (E-glass, Spectra®, Vectran® and Zylon®) of fibers used in this study. The goal of this research is to reveal the role of fiber type in the performance of their composites. To achieve the goal, several 3D orthogonal woven preforms from E-glass fibers in y- and z-direction with varying fibers in x- direction. The fibers in x-direction were Spectra®, Vectran® and Zylon®. The preforms were resin infused using vacuum assisted resin transfer molding technique (VARTM). The final composites were tested for their impact performance (Tup impact, Izod impact and Charpy impact) and tensile strength in x- and y- directions. Analytical properties such as thickness, constituents and total fiber volume fraction were also measured or calculated from exiting models. The fiber and tow tensile properties were determined to understand the role of fiber type in performance of their composites. This was achieved by comparing the fiber and yarn tensile properties to their corresponding composites. The role of fiber in determining the impact properties of composite was also revealed by comparing the tensile energy required to break the fibers with the energy required to break their corresponding composites. Details of the experimental methods used are given in the next chapter.

4. Experimental

4.1 Single fiber and yarn tensile testing

4.1.1 Materials

Four type of commercial available high performance fibers were used in this study including Spectra®

1000(UHMWPE), Vectran® HT (polyarylate fibers), Zylon® HM (PBO fibers), and glass fibers (Hybon®

2022 275 tex, Hybon® 2022 735 tex and Hybon® 2002 2400 tex). The Spectra® fibers were supplied from

Honeywell, USA; the Vectran® fibers were supplied from Kuraray Co., Japan; the Zylon® fibers were supplied from Toyobo Co., Japan; and the Hybon® series glass fibers were supplied by PPG Industries

Fiber Glass Americas.

The Table 3 shows the properties provided by the manufacturers of the four types of yarns.

Table 3 Published yarn data.

Hybon® fiber glassd Vectran® Zylon® Yarns Spectra® 1000 2400 HT HM 275 TEX 735 TEX TEX Honeywell Kuraray Toyobo Supplier International, PPG Fiber Glass Co., Ltd. Co., Ltd. Inc. Filaments 240 a 300b 996c 378d 1960d 3920d (count) Denier(g/9000m) 1300 a 1500b 1476c 2475d 6615d 21600d

Density (g/cc) 0.97 a 1.40b 1.56c 2.58 e 2.58 e 2.58 e Tenacity 5.48 or 38 e 30 e 42 e 10.9d 9.61d (gf/denier) 5.62d Modulus 1250 e 830 e 1800 e N/A N/A N/A (gf/denier) Elongation at 3.1 e 2.8 e 2.5 e 3.5 e 3.5 e 3.5 e break (%) a Honeywell International Inc. data. https://www.honeywell-spectra.com/products/fibers/ retrieved on 03/01/2016 b Kuraray Co., Ltd. data. http://www.vectranfiber.com/properties/tensile-properties/ retrieved on 03/01/2016 c Toyobo Co., Ltd. data http://www.toyobo-global.com/seihin/kc/pbo/zylon_bussei.html#sds retrieved on 03/01/2016 d PPG Fiber Glass data http://www.ppgfiberglass.com/Products/HYBON%C2%AE-Direct- Rovings.aspx retrieved on 03/01/2016 e Typical properties of synthetic yarns table by FIBERLINE To verify the linear density for each type of high performance fibers, ASTM D1907 was followed and each type of high performance yarns. Five specimens were taken from the yarn packages to determine the linear density. Each specimen’s length was determined by using a reel. Each specimen has 40 wraps of yarn on the reel and the length equals 60 yards since each wrap is 1.5 yards long. The mass of each specimen’s weight was weighted and recorded to calculate the actual linear density of each type of high performance yarns. The Table 4 shows the testing results of the high performance fibers linear density.

Table 4 Yarn linear density testing results.

Avg. specimen Calculated Manufacturer’s No. of Fiber Type weight linear density Linear density Specimens (g) CV, % (denier) (denier) Spectra® 5 8.055 0.33% 1321.36 1300 Vectran® 5 9.550 0.15% 1566.60 1500 Zylon® 5 8.913 0.04% 1462.11 1476 275 tex 5 14.752 0.26% 2419.95 2475 Fiber 735 tex 5 43.024 0.09% 7057.74 6615 Glass 2400 tex 5 131.098 0.07% 21505.58 21600

From Table 4, the measured results are very close to the linear density provided by the manufacturer. The linear density data provided by the manufacturer is concluded from higher number of measurements compared to what is reported in Table 3, the high performance yarn linear density which is provided by the manufacturer are considered. Individual data for each specimen for each specimen are given in Appendix

4.1.2 Specimen preparation

For each type of high performance fibers, the single filament specimens were randomly and carefully selected from a certain length of fiber bundle that cut from the yarn package by using a sharp razor blade.

Then the single fiber was mounted on paper frames by using epoxy glues and tapes that shown in Figure

34. The gauge length of single filament fiber specimens is 2.5 cm (1 inch) and each specimen was assigned with a number for differentiation.

For tensile yarn testing, specimens were continuously selected from the yarn package while conducting the test, the gauge length of yarn specimens is 25 cm (10 inch).

Single filament fiber specimens were prepared according to ASTM 3822 and yarn tensile strength testing specimens were prepared according to ASTM 2256. The number of single fiber specimens was 30 specimens for Spectra®, Vectran®, Zylon® single fiber, 20 specimens for fiber glass and 10 specimens for

48 filament yarns. Q Test machine manufactured by MTS was used for tensile testing. All specimens were stored in the Physical Testing Lab, College of Textile, for 24 hours conditioning before conducting the tensile testing. The tensile testing lab conditions are 70° F with 65% relative humidity.

Care was taken to keep the specimens and the yarn packages fully covered by black plastic bag to protect the materials from the UV-VIS damage since high performance fibers are known to their strength loss if subjected to UV-VIS rays.

(a) (b) (c)

Figure 34 Single fiber tensile testing preparation (a) dimensional size of the cardboard frame, (b) actual

cardboard frame, (c) specimen mounted between the grips in gauge length

4.1.3 Tensile testing

Single filament tensile testing

ASTM D3822 was followed to determine the tensile strength of single fiber filament, 2.268 kg (5 lbs) load cell was used in testing the single fiber tensile strength, with 2.5 cm (1 inch) gauge length. The grips are equipped with rubber for better pressure distribution and reduce the stress concentration and possibility of the filament slippage or breakage inside the grips. The elongation rate of 0.5 mm/min was applied and grip pressure was 4.9 k/cm2 (70 psi). The tensile strength testing was conducted on using MTS Q Test machine with constant elongation rate (CRE), which is located in the Physical Testing Lab, College of Textiles, NC

State University. Observations on specimens’ break mode were recorded during the testing and specimen waste after the tensile testing was collected for further examination post testing. The specimens broke inside the grips were noted as the breakage didn’t happen in the gauge length, and they were marked and not considered in the calculation of the average tensile strength.

Yarn tensile testing

All types of yarn fiber packages were transported to the Physical Testing Lab for conditioning at least 24 hours. Snubbing grips were used for mounting the yarn specimens and 1000 lbs load cell was selected for tensile testing on MTS Q Test machine with constant elongation rate. For each yarn specimen, the gauge length is 10 inch and the crosshead speed was 12 inch/min. The specimen was wrapped on the snubbing grips and the grip pressure was 60 psi. All the tests were conducted under the direction of ASTM 2256.

4.2 3D woven preform

4.2.1 Materials

For the 3D orthogonal woven preform, 5 different high performance fiber including Spectra®, Vectran®,

Zylon®, Hybon® 2022 E-glass filament yarn and Hybon® 2002 E-glass filament yarn were used in weaving the 3D orthogonal woven preforms. The warp yarn was Hybon® 2002 E-glass filament yarns with

50 linear density of 2400 tex and the Hybon® 2022 E-glass filament yarns with linear density of 276 tex was used as for z-yarns. The Spectra®, Vectran® and Zylon® were separately used for the weft yarns and 3D preform samples with 2 m length were manufactured by using 3D weaving machine shown in Figure 35 donated by 3TEX, Inc. and housed in the composite core facility, College of Textiles, NC State University.

Figure 35 View of the 3D weaving machine

All 3D preform samples were woven with 3 layers of warp yarns and each layer had 102 individual yarns.

Each warp yarn in a given layer was drawn in reed dent. The z-yarns had the total number of 103 yarns and drawn in straight draft into four harnesses, the reed plan was the same with warp yarns. The Z-yarns were woven in plain weave structure. Each preform width was 40 cm in reed and 43 cm wide after woven with selvage.

In total, 3 different 3D orthogonal preforms were produced with different weft yarns and pick densities.

Figure 36 shows the surface images of all 3 layers 3D orthogonal woven preforms with Spectra®, Vectran® and Zylon® woven as weft yarns. The polymeric high performance fibers such as Spectra®, Vectran® and

Zylon® and related 3D woven preforms were fully covered by black plastic bags to block the UV-VIS and protect the fibers and preforms from degradation damage.

(a)

(b)

(c)

Figure 36 3D woven fabric surface. (a) Spectra®; (b) Vectran®; (c) Zylon®.

All the 3D preforms were woven at the calculated theoretical maximum filling density by using equations

(1), (2), (3) and (4) from the model developed by Ince [44]. Table 5 shows the calculated maximum filling construction for each of the three high performance fibers.

Table 5 Calculated maximum filling density for each high performance fiber

Yarn Yarn Yarn Fiber Yarn Linear Aspect Width thickness Yarn density Total denier Yarns Density direction density Ratio (w) (t) denier g/cm3 mm mm picks/cm/layer denier/cm/layer

z 2475 2.51[44] 8.03[44] 1.211 0.151 N/A N/A Fiber x 6615 2.50[44] 7.12[44] 2.642 0.371 7.16 47380 glass y 21600 2.65 7.35[44] 3.331 0.453 2.20 47559

Spectra® 1300 0.97 7.00 1.864 0.266 9.93 12904

x Vectran® 1500 1.40 7.00 1.667 0.238 11.00 16507

Zylon® 1476 1.56 7.00 1.566 0.224 11.65 17193

4.2.2 3D orthogonal woven preform construction

This interest in this work is to construct jammed construction to obtain high fiber volume fraction and consequently high composite performance. For this reason, the maximum pick density was calculated to produce jammed structures from high performance fibers. The detail of the calculations are provided later.

In jammed structures, three yarns are touching with each other and compression produced in this structure that lead the yarn cross section close to rectangular shape for flat continuous filament yarns.

Figure 37 Structure of 3D orthogonal preform. [55]

The Figure 37 shows the structure of 3D orthogonal woven preform, also the equations from this model of

3D woven preforms in this research allow the calculation of the theoretical thickness of preforms, FVFs of fibers in different direction ( X-, Y-, Z-direction and total FVF) and maximum filling construction.

Equations (1) and (2) [44] were used to calculate the width and thickness of the rectangular shaped yarns in different directions.

휌푙푘퐴푅푘 푤푘 = √ 5 (1) 훷푘휌푣푘(9×10 )

휌푙푘 푡푘 = √ 5 (2) 훷푘휌푣푘퐴푅푘(9×10 )

푝푥 = 푤푥 + 푡푧 (3)

푝푦 = 푤푦 + 푤푧 (4)

푤푈 = 2푝푦 = 2(푤푦 + 푤푧) (5)

푙푈 = 2푝푥 = 2(푤푥 + 푡푧) (6)

Where:

K: yarn direction (x-, y- and z-direction)

wk: yarn width(cm)

tk: yarn thickness(cm)

Φk: packing factor (0.6)

ρlk: yarn linear density(tex)

ρvk: fiber volumeric density(g/cc)

ARk: aspect ratio

px: yarn spacing in x-direction

py: yarn spacing in y-direction

wU: repeat unit width

lU: repeat unit length

Equations (3) and (4) [44] were used to calculate the yarn spacing in X- and Y-direction and equations (5) and (6) were used to calculate the size of the repeat unit in 3D orthogonal woven preforms with plain weave for each type of high performance fibers. And wU is the repeat unit width in X-direction, lU is the repeat unit length in Y-direction.

4.2.3 3D Woven preform thickness

For each type of high performance fibers, three fabrics with size 425 mm width and 70 mm length were cut to measure preform thickness and constituent yarn weights using raveling technique to separate X yarns, Y yarns and Z yarns. The determination of the dry preform thickness of the 3D woven preforms, followed the

ASTM D1777 using tester in the Physical Testing Lab and the foot diameter was 28.7 mm and the applied pressure for thickness measurement were 4.14 kPa.

푡푃 = 푛푡푦 + (푛 + 1)푡푥 + 2푡푧 (7)

Equation (7) was used to calculate the thickness of 3D orthogonal preforms with plain weave for each type of high performance fibers in x-direction. And n is the number of layers.

Table 6 shows the comparison between the theoretical thickness which calculated by using equation (7) and the measured thickness of the 3D woven preforms. Additionally, the theoretical fiber volume fraction of X-

, Y- and Z-yarns were compared to the measured values. The measurement data for thickness of preforms are available in Appendix B.

Table 6 Comparison between the measured preform thickness and the theoretical thickness

3D Orthogonal Woven Preform thickness Fiber Theoretical thickness(mm) Measured Average Thickness(mm)

Spectra 2.73 3.20

Vectran 2.61 3.41

Zylon 2.56 3.20

4.2.4 3D orthogonal woven preform FVFs

Fiber volume fraction is a critical factor that affect the mechanical properties of final composite materials.

As fiber is the major load carrier and much stronger than resin in tensile property, the resin prevents fibers from external damage while transferring the load to the fibers inside the composite. And, higher fiber volume fraction will lead higher tensile strength of the composite. However, higher fiber volume fraction will make the fibers more compact and resin’s ability to penetrate through compacted fibers. In this situation, longer resin infusion time or higher pressure are needed to reduce the defects inside the final composites.

Equations (8), (9) and (10) were used to calculate the predicted FVFs for fibers in different direction of the

3D orthogonal preforms.

2(푛+1)푤푥푡푥푤푈 퐹푓푥 = (8) 푤푈푙푈푡푃

2푛푤푦푡푦푙푈 퐹푓푦 = (9) 푤푈푙푈푡푃

2(2푡푃+2푤푥)푤푧푡푧 퐹푓푧 = (10) 푤푈푙푈푡푃

Substituting equations (3), (4), (5), (6) and (7) into equations (8), (9) and (10), we get FVF equations for jammed structures with rectangular shaped yarns. Ffx is the FVF of fibers in X-direction, Ffy is the FVF of fibers in Y-direction and Ffz is the FVF of fibers in Z-direction. And n is the preform layers.

(푛+1)푤푥푡푥 퐹푓푥 = (11) (푤푥+푡푧)[푛푡푦+(푛+1)푡푥+2푡푧]

푛푤푦푡푦 퐹푓푦 = (12) (푤푦+푤푧)[푛푡푦+(푛+1)푡푥+2푡푧]

[푛푡푦+(푛+1)푡푥+2푡푧+푤푥]푤푧푡푧 퐹푓푧 = (13) (푤푥+푡푧)(푤푦+푤푧)[푛푡푦+(푛+1)푡푥+2푡푧]

Table 7 shows the calculated theoretical FVFs of fibers in X-, Y- and Z-direction for preforms with different type of high performance fibers as the filling yarns.

Table 7 Theoretical FVFs for preforms with different type of high performance fibers

Fiber type X yarn FVF (%) Y yarn FVF (%) Z yarn FVF (%) Total FVF (%)

Spectra 36.1 36.6 3.4 76.1

Vectran 33.4 38.1 3.6 75.2

Zylon 31.9 39.0 3.8 74.7

4.2.5 3D woven preform areal density

To determine the areal density of 3D orthogonal woven preforms, one specimen with 70 mm length in Y- direction were cut to measure the weight for each type of high performance fibers. Equation (14) was used to calculate the areal densities. WP is the preform specimen weight and AP is the preform specimen area.

푊 ⍴ = (14) 퐴 퐴

Table 8 shows the measured specimens’ size, weight and calculated preform areal density. The result indicates 3D orthogonal preforms with Vectran® and Zylon® have the close areal density which conform their fibers linear density and construction filling yarn density as both yarns of Vectran® and Zylon® fibers have very similar linear density and calculated maximum filling yarns construction.

Table 8 Preforms’ areal density measurement

Fabric Length in Length in preform areal Fiber type weight X-direction Y-direction density (g) (mm) (mm) (g/m2) Spectra 76.04 425 70 2556 Vectran 86.73 425 73.8 2803 Zylon 82.98 425 70 2789 4.2.6 Composite areal density

To determine the areal density of 3D orthogonal woven preform reinforced composites, composite specimens for Dynatup impact test were used to calculate the areal density for each individual specimen.

The calculated areal density was used to normalize the peak force and perforating energy of the Dynatup impact tests. The normalization of the peak force and energy provide a mean to better understand Dynatup impact resistance performance in terms of fibers types. The weight and areal for each individual Tup impact specimens were measured and equation (14) was used to calculate the areal density. Table 9 shows the

58 average areal densities for composites reinforced by difference type of high performance fibers in x- direction. The detailed measurement data is available in Appendix C.

Table 9 Composite specimen areal density measurement

Average Average specimen Average specimen Number of composite areal Fiber type weight area specimens density (g) (m2) (g/m2)

Spectra 11 15.63 0.004 3809

Vectran 10 19.80 0.005 4398

Zylon 10 18.06 0.005 3982

4.2.7 z-yarn crimp determination

The Z yarns were separated from the dry preforms and their straight lengths were measured. The length of the fabric is also measured and the difference between the yarn straight length and fabric length is calculated. The difference will be reported in percentage based on preform specimen length to indicate the z-yarn crimp. In 3D orthogonal woven composites, z-yarn has very important role in delamination resistance under the impact testing.

4.3 Composites formation

4.3.1 Materials

The resin system was the DERAKANE 8084 Epoxy Vinyl Ester Resin donated by ASHLAND Inc.. The initiator was peroxide type initiator NOROX MEKP-925H and the typical properties of the components in this resin system are given in Table 10.

Table 10 Additive in resin system (a) Typical liquid resin properties of Derakane 8084, (b) Typical

properties of initiator NOROX MEKP-925H

Property Value

Density, 25°C 1.02g/mL

Dynamic viscosity, 25°C 360 mPa·s(cP)

Kinematic viscosity 350 cSt

Styrene content 40%

Shelf life, dark, 25°C 6 months (a)

Property Value Active oxygen 9.0%, max Form Liquid Color Water white Specific gravity @ 25°C+/-4°C 1.10 (b)

4.3.2 Resin infusion

The 2 meter length preforms were cut into half meter length before the resin infusion. Each of three different half meter 3D preforms was placed over a release film on a glass table. Resin inlet spiral tube and resin outlet spiral tube were placed on each end of the 3D preform in x-direction as the x-direction was selected as resin flow direction. The final vacuum bagging as conducted by using the double sided tape and the vacuum system was examined for leakage by using the Vacuummobile® reader and the Amprobe®

TMULD-300 ultra-sonic leak detector.

The resin for infusion was prepared in the fume hood located in the Dyeing and Finishing Lab, College of

Textiles, NC State University. The resin gel time is highly sensitive to the room temperature and the curing agent amount. Table 11 shows the typical gel times of Derakane 8084 at different temperatures with

60 respectively different amount of MEKP-925H, Cobalt Naphthenate-6% and DMA. In this resin system, the

MEKP-925H is the initiator, Cobalt Naphtenate-6% is the promoter and DMA is the accelerator.

Table 11 Typical Gel Times Using NOROX MEKP-925H and Cobalt Naphthenate-6%

Temperature 15+/-5 minutes 30+/-10 minutes 60+/-15 minutes

3.0 phr MEKP 3.0 phr MEKP 2.5 phr MEKP

0.6 phr 0.4 phr 0.4 phr 18°C/65°F CoNap6% CoNap6% CoNap6%

0.3 phr DMA 0.3 phr DMA 0.1 phr DMA

2.0 phr MEKP 2.0 phr MEKP 1.5 phr MEKP

0.5 phr 0.4 phr 0.3 phr 24°C/75°F CoNap6% CoNap6% CoNap6%

0.3 phr DMA 0.2 phr DMA 0.05 phr DMA

2.0 phr MEKP 1.5 phr MEKP 1.5 phr MEKP

0.3 phr 0.3 phr 0.3 phr 30°C/85°F CoNap6% CoNap6% CoNap6%

0.2 phr DMA 0.05 phr DMA 0.025 phr DMA

To produce the final composite material reinforced by the 3D woven preforms, the infusion should be finished before the resin start turning into gel. When the resin start gelation, the resin flow rate will be slowed. The sample resin infusion time should long enough to avoid gelation and solidification of the resin before the preform fits fully saturated by the resin. To get the preforms completely wetted before the resin gelation the curing agent formula with 1% MEKP and 0.2% CoNap6% was selected to conduct the resin mixing, no accelerator and retarder was added. The initiator MEKP-925H was added lastly and the resin was transported from the fume hood to the degassing oven. The degassing continued as 20 min and the resin moved to the glass table to start the infusion. Resin flow front position was recorded to compare wetting time for each preform. The environment temperature in Dyeing Lab was 22°C and the humidity was 50%-55%. A pressure of 100 kPa was used as vacuum level for the vacuum bagging.

4.4 Mechanical testing

Methods and experimental apparatus to determine mechanical properties of composites are described in this section.

4.4.1 Panel sampling

Figure 38 Shows the composite panels sampling plan before cutting for each sample to maximize the utilization of the produced composites. According to the ASTM standard for textile composite, the size of specimen and strain gauge width should be wider than unit cell width of textile preform to get reliable test data. Also, according to the ASTM D6856, at least two unit cells in their short dimensions should be included in each composite specimen. Both of these recommendations were taken into account in the cutting plane.

Figure 38 Cutting plan for the mechanical testing specimens

Each unit cell dimension of composite specimens was also calculated to decide the minimum specimen size for composite specimens. Equations (5) and (6) were used to calculate the minimum size of the repeat unit in the preforms with different high performance fibers as filling yarns.

Table 12 shows the minimum dimension of unit cells for each type of composite used. From the table, all the specimens size in the cutting plan figure meet with the minimum requirement for the textile composite specimen. It should be noted that E-glass fibers are arranged in the y-direction and when applicable tests were performed in x- and y-direction.

Table 12 Minimum size of the repeat unit for preforms with each high performance fibers

repeat unit size Composite form Y-direction length(mm) X-direction length(mm)

Spectra® 4.03 9.08

Vectran® 3.63 9.08

Zylon® 3.43 9.08

4.4.2 Tensile strength testing

ASTM D3039 was followed to determine the tensile performance of composites in x- and y-directions.

MTS Landmark, 250 kN load cell capacity, universal testing device available at Composite Core Facility,

College of Textiles, NC State University was used to test tensile properties of composite specimens.

Specimen size for each panel has 152 mm in length and 30 mm in width for panel 1, and 170 mm in length and 27 mm in width for panel 2. Preliminary testing were conducted to find optimum gripping and gauge length to get specimen failure in the gauge length area that is minimum 5 mm away from the jaws. For specimens in y-direction, optimum failure was obtained at 55 mm gripping length and 60 mm gauge length.

Cross head speed was 1 mm/min and optimum gripping pressure was selected as 13.5 MPa to impede slippages and reduce the crushing of composite specimens in the gripping area. Laser extensometer was

64 used to measure strain accurately. Two parallel retro reflective tapes with at least 15 mm apart were allocated in the middle of specimen gauge length, the distance between two tapes is wider than the minimum unit cell dimension of the 3D orthogonal woven preform. Figure 39 shows the composite tensile tester and its hydraulic power unit.

(a)Composite tensile property tester

(b)Composite tensile property tester hydraulic power unit Figure 39 Composite Tensile property tester. (a) Tensile property tester; (b) Hydraulic power unit

4.4.3 Dynatup impact property

ASTM D3763 was followed for testing puncture property of composite specimens. Instron® drop-tower impact test machine available at Composite Core Facility, College of Textiles, NC State University was used to test puncture properties of composite specimens. The specimen size for this test was square with 66 x 66 mm.

Figure 40 shows the tester in the Composite Core Facility, College of Textiles

Figure 40 Tup impact property tester.

4.4.4 Charpy impact property

ASTM D6110 was followed for testing unnotched Charpy impact property of composite specimens.

Instron® Ceast 9050 impact tester which is available at Composite Core Facility, College of Textiles, NC

State University was used to determine the Charpy impact strength. The specimen size for this property testing is 127 mm in length and 12.7 in width. Figure 41 shows the Charpy impact tester with 22 J hammer.

(a) (b) Figure 41 Charpy Impact tester. (a) Instron® Ceast 9050 Impact tester; (b) Charpy impact testing table.

4.4.5 Izod Impact property

ASTM D256 was followed for testing unnotched Izod Impact property of composite specimens. Instron®

Ceast 9050 impact tester was used to determine the Izod Impact strength. The specimen size for this property testing is 63.5 mm in length and 12.7 in width.

Figure 42 shows the Izod impact tester in the Composite Core Facility, College of Textiles

(b)Izod impact tester hammer

(a) Izod impact property tester

Figure 42 Izod Impact property tester. (a) tester; (b) hammer; (c) clamping table.

4.5 Statistical Analysis

Tukey multiple comparison ANOVA statistical analysis were conducted to assess whether there are significant differences between properties of fibers, yarns and composites from the four high performance fibers used in this research, namely Spectra®, Vectran®, Zylon® and E-glass.

5. Results and discussion 5.1 FVFs and z-yarn crimp

The dry fabric weight of 3D woven preform with size 425 mm x 70 mm for Spectra® and Zylon®, and 425 mm x 72.8 mm for Vectran® was measured. The thickness of the dry preforms was also measured to calculate the preform specimen volume. The yarns in each direction are separated and their weight was measured for calculating the fiber volume fractions. The theoretical fiber volume fraction (FVF) is calculated by using equation (11), (12) and (13). The comparison between the measured FVFs and theoretical FVFs, and z-yarn crimp are reported below. Figure 43 shows the comparison between the measured dry preform thickness, theoretical thickness and measured composite thickness. The measured preform thickness is higher than the theoretical thickness for all types of composites. This might be caused by the assumed values of yarn aspect ratio. However, the final composites exhibited measured thickness that is lower than the theoretical dry preform thickness except the composites with Vectran® fibers, the reason is the preform with Vectran® yarns in x-direction has the highest measured z-yarn crimp as it can be seen in Figure 45. However, the difference between the theoretical thickness and measured composite thickness is insignificant. Figure 44 shows the comparison between the measured FVFs and theoretical

FVFs of x-, y-, and z-yarns. The measured FVFs is lower than the theoretical FVFs which is reasonable as the VARTM method can lead to the reduced FVF in composite. Figure 45 shows measured z-yarn crimp results and compared with theoretical z-yarn crimp. The Vectran® has the highest z-yarn crimp because composites with Vectran® fibers have the highest measured thickness of the preforms and thickness of composite as seen in Figure 43.

4.00

3.50

3.00

2.50 Theoretical Preform Thickness (mm)

2.00 Average Measured Preform Thickness (mm) 1.50 Thickness, Thickness, mm Average Measured Composite Thickness (mm) 1.00

0.50

0.00 Spectra Vectran Zylon

Figure 43 Dry preform thickness compared with composite thickness

Figure 44 Fiber volume fractions for each type of high performance fibers. (a) x-yarns; (b) y-yarns; (c) z-

yarns.

40%

35%

30%

25%

20% Measured FVF

FVF, % FVF, Theoretical FVF 15%

10%

0% Spectra Vectran Zylon

(a)

45%

40%

35%

30%

25% Measured FVF

FVF, % FVF, 20% Theoretical FVF

15%

10%

0% Spectra Vectran Zylon

(b)

2% Measured FVF

FVF, % FVF, Theoretical FVF 2%

0% Spectra Vectran Zylon

(c)

160%

140%

120%

100%

80% Measured z-yarn crimp (%) Theoretical z-yarn crimp (%)

60% Yarncrimp, %

40%

20%

0% Spectra Vectran Zylon

Figure 45 Z yarn crimp

5.2 Resin infusion performance

The preliminary infusion experiments indicate that the resin with formula of 1% MEKP and 0.2% CoNap

(6%) had the longest gelation time without using retarder agent. MEKP is short for methyl ethyl ketone peroxide and sold as a 9% active-oxygen solution of MEKP and plasticizer. It is a non-foaming initiator.

From the resin provider technical manual document, the promoter CoNap-Cobalt Naphthenate with 6% active cobalt has a recommended 0.2% for the resin used in this research. The preliminary resin infusion trial showed that the maximum infusion time before the resin turn into gel is 180 min. No retarder was used in this research. The environmental temperature was 18°-19°and the humidity was 55%-60%. Figure 46 shows the recorded resin flow front line during the infusion process, one record every 3 min up to 15 min and then the flow front line was marked every 5 minutes considering the slow resin flow rate after about 15 minutes. The distance between inlet and outlet tubes was 400 mm for all 3D orthogonal woven preforms.

Figure 46 Infusion resin flow front lines and time. (a) Spectra®; (b) Vectran®; (c) Zylon®. Blue arrows

indicate the resin flow direction.

(a)

(b)

(c)

From Table 13, infusion time for three high performance fibers are recorded and Zylon® has the longest infusion time and Vectran® has the shortest infusion time. However, preform with Spectra® fiber in X- direction has the infusion time close to that of the preform with Zylon® fibers.

Table 13 Total infusion time for each type of high performance fiber

Fiber Type Infusion Time (min)

Spectra® 160

Vectran® 90

Zylon® 180

Figure 47 shows the recorded resin flow front line distance and time during the resin infusion process. It indicates that 3D orthogonal woven preforms with Spectra® fibers and Zylon® fibers as filling yarns have almost the same flow rate during the infusion. Table 14 shows the calculated fiber surface area for preforms with different type of high performance fibers in x-direction per meter square preform. The details of calculation are available in Appendix D.

Table 14 Fiber surface area

Fiber Fiber surface area (m2/m2 preform) Spectra® 84.22

Vectran® 93.33

Zylon® 169.16

The preform with Vectran® as the filling yarns exhibited the fastest resin flow rate. From previous maximum filling density construction table, composites with Vectran fibers and Zylon® fibers have very close maximum density which is higher than that of Spectra® fibers. But Zylon® fibers have much higher fiber surface area than that of Vectran® and Spectra® fibers which can lead to longer infusion time.

Figure 47 Infusion resin flow front line distance to the inlet.

5.3 Cross-sections

Cross-section pictures of different composites with each type of high performance fibers were taken by using the electronic microscope available in the Composite Core Facility, College of Textiles, NC State

University. Figure 48 and Figure 49 show the cross-section pictures of the composite specimens in x- and y-direction. From the figures, the resin went through the Spectra® yarns very well but had poor wetting in case of Vectran® and Zylon® yarns. Fiber surface area can also contribute to this as the Zylon® fibers have the highest surface area, Spectra® fibers and Vectran® fibers have the close fiber surface area which indicate the poor wettability of Spectra® fibers to vinyl ester resin. Fiber glass were well wetted in all composite specimens, which is indication of fiber glass possessed better wetting ability than polymeric fibers.

Figure 48 X-direction ross-sections of composites with different type of high performance fibers. (a)

Spectra®; (b) Vectran®; (c) Zylon®.

(a)

(b)

(c)

(a)

(b)

Spectra®; (b) Vectran®; (c) Zylon®.

5.4 Single fiber tensile testing

For high performance polymeric fibers, the difference in the stress-strain curves shows the tensile behavior for different high performance fibers and these differences are strongly affected by the molecular structures, molecular weight, crystallinity and preferential orientation of the fibril structures. In this research, we can divide the high performance polymeric fibers into 3 different group based on the characteristics of the materials such as the crystallinity and preferential orientation of the fibril structures. For Spectra® 1000 fiber, they are polyethylene fiber with low crystallinity and highly oriented fibril structures. For Vectran®

HT fibers, they are high tenacity polyarylate fibers with high crystallinity and slightly curved fibril structures. For Zylon® HM fibers, they are high modulus PBO fibers with high crystallinity and highly oriented fibril structures.

The tensile behavior of the three e-glass fibers with different linear densities was also examined. E-glass fibers are isotropic material and they have simply Hookean stress-strain curves (stress-strain relationship is linear).

Figure 50 shows stress-strain (σ-ε) curves for the Spectra® fibers, Vectran® fibers, Zylon® fiber and fiber glass with different linear densities. Spectra® s1000 fibers, due to the highly oriented fibril structures, stress-strain curve shows almost linear behavior in the initial stage of loading which indicate the stress applied to the specimen is almost linearly proportional to the strain. After the initial stage, a clear reduction in slope with increase in the displacement and with further strain the stress leveled off until the fiber breaks, which can be attributed to the low crystallinity and disentanglement between the molecules. For the

Vectran® HT fibers, curve shows almost linear behavior in the initial stage of loading and this is due to the high crystallinity, as the loading increase, the curvature of the fibril structures changes to highly oriented structures and increase the fiber modulus. For Zylon® HM fibers, due to their high crystallinity and high oriented structures, the tensile behavior is almost linear for the entire stress-strain relationship. The fiber tensile strength and modulus is proportional to the strain as the loading increasing. E-glass fibers have the

80 linear relationship between the tensile strength and strain which is reasonable as glass have the simply

Hookean law tensile stress-strain.

Figure 50 Tensile behavior curves for the high performance single fiber. (a) Spectra® fibers, (b)

Vectran® HT fibers, (c) Zylon® HM fibers, (d) fiber glass from yarn with linear density 275 tex, (e)

fiber glass from yarn with linear density 735 tex, (f) fiber glass from yarn with linear density 2400

tex.

Tencity,gf/denier 10

0 0.00% 5.00% 10.00% 15.00% 20.00% 25.00% Strain, %

(a)

45 40 35 30 25 20

15 Tenacity,gf/denier 10 5 0 0 1 2 3 4 5 6 7 Strain, %

(b)

50 45 40 35 30 25 20

15 Tenacity,gf/denier 10 5 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Strain, %

(c)

9 8 7 6 5 4

3 Tenacity,gf/denier 2 1 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Strain, %

(d)

18 16 14 12 10 8

6 Tenacity,gf/denier 4 2 0 0 1 2 3 4 5 Strain, %

(e)

18 16 14 12 10 8

6 Tenacity,gf/denier 4 2 0 0 1 2 3 4 5 Strain, %

(f)

The tensile stress and modulus comparison for all high performance fibers are indicated in Figure 51 and

Table 15. The table shows the comparison between the testing results and published data, and manufacturer’s data. The individual testing observations for all specimens are available in Tables E1-E6,

Appendix E.

30 Spectra 25 Vectran 20 Zylon 15 Fiber glass 275 tex

Tenacity, Tenacity, gf/denier 10 Fiber glass 735 tex

5 Fiber glass 2400 tex

0 0 2 4 6 8 10 Strain, %

Figure 51 Typical high performance fibers tensile behavior

Table 15 Single fiber tensile properties comparison

Avg. Peak Avg. Break Avg. Fiber Avg. Fiber Denier Tenacity Fiber Type Load Strain Modulus (denier) (gf) (%) (gf/denier) (gf/denier)

Current research 5.42 171.38(8%) 13.49(34%) 892.92(17%) 31.62(8%) Spectra® Published[36] 5.42 198.24 6.89 1153.68 36.61 s1000 Manufacturerb 5.42 N/A N/A 775-1580 25.5-43 827.55(19%) Current research 5.0 152.72(14%) 4.92(10%) 30.54(14%) 582.77(13%)d Vectran® HT Published[36] 2.505 83.04 3.43 643.38 d 33.15

Manufacturerb 5.0 N/A N/A 600 d 25.9

Current research 1.48 52.30(12%) 2.60(11%) 1653.84(16%) 35.34(12%)

Zylon® HM Published[36] 1.48 51.35 2.41 1532.29 34.77

Manufacturera 1.48 N/A 2.5 1578.5 42.0

Current research 6.548 35.21(21%) 2.94(21%) 257.43(40%) 5.38(31%) 275 Published N/A N/A N/A N/A N/A tex Manufacturerc 6.548 N/A N/A N/A 5.48 or 5.62

Current research 3.375 34.28(30%) 3.34(27%) 346.75(24%) 10.16(30%) Fiber 735 Published N/A N/A N/A N/A N/A Glass tex Manufacturerc 3.375 N/A N/A N/A 10.9

Current research 5.51 53.66(31%) 3.21(22%) 334.78(25%) 9.74(31%) 2400 Published N/A N/A N/A N/A N/A tex Manufacturerc 5.51 N/A N/A N/A 9.61 Number between “( )” are CV, % a Toyobo data, http://www.toyobo-global.com/seihin/kc/pbo/zylon_bussei.html#sds b Textile World’s Man-Made Fiber Chart c PPG Fiber Glass http://www.ppgfiberglass.com/Products/HYBON%C2%AE-Direct-Rovings.aspx d Initial modulus.

5.5 Yarn tensile testing

The tensile behaviors of yarns are affected by various factors. The factors affect the tensile strength and tensile behavior of yarns include: (1) uncertainty in fiber statistical parameters, individual fibers are not exactly the same as they might have different diameters, strain, damages introduced during processing and handling during packaging and shipping; (2) Yarns are also tested at longer gauge length that leads to increase the possibility of increasing weak points and flaws; (3) Misaligned fibers during testing can lead to non-uniform loading; (4) Total number of fibers in the yarn could be less than expected due to filament break during processing and handling.

From Figure 52 and Figure 53, it can be noticed that the tensile behavior of yarns and tensile behavior of single fibers are very close to each other for each type of high performance fibers. For Spectra® fiber, the modulus of yarn has a stage of decreasing after the initial loading stage which is close to the Spectra® single fiber tensile behavior; for Vectran® fiber, the yarn has a modulus increasing stage after the initial loading stage which is similar to Vectran® single fiber tensile behavior; for Zylon® fiber, the tensile behavior is almost the same as the tensile behavior of Zylon® single fiber, the tensile strength is proportional to the strain; for fiber glass with different linear density, they all obey the Hookean law tensile behavior that their tensile strength is proportional to the strain.

However, Figure 53 shows there are some difference between the ultimate tensile strength and break strain for each type of high performance fibers. For Spectra®, the yarn has higher ultimate tensile strength but lower strain which indicate Spectra® has better performance in yarn form than its single filament; for

Vectran® fiber, the yarn has lower ultimate tensile strength and lower break strain and the stress-strain curves for both are almost exactly coincided with each other. This indicate that single fiber and yarn of

Vectran® have the consistent tensile behavior; for Zylon® fiber, the yarns has lower ultimate tensile strength and higher break strain and the linear curve indicates the high crystallinity of PBO fibers; for fiber glass, the yarn with 275 tex linear density has higher ultimate tensile strength but lower break strain than its single fiber, for the other two fiber glass with different linear densities, their single fibers have higher

86 ultimate tensile strength and break strain than the yarns. For the yarns with higher number of filaments, their stress-strain curves are not linear at the end of testing because it is well known that filaments are not breaking at the same time when under the tensile loading.

Figure 52 Tensile curves for the yarns of high performance fibers. (a) Spectra®, (b) Vectran®, (c)

Zylon®, (d) fiber glass with linear density 275 tex, (e) fiber glass with linear density 735 tex, (f) fiber

glass with linear density 2400 tex.

Tenacity,gf/denier 10

0 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 Strain, %

(a)

Tenacity,gf/denier 10

0 0.00 1.00 2.00 3.00 4.00 5.00 Strain, %

(b)

Tenacity,gf/denier 10

0 0 0.5 1 1.5 2 2.5 3 3.5 Strain, %

(c)

9 8 7 6 5 4

3 Tenacity,gf/denier 2 1 0 0 0.5 1 1.5 2 2.5 3 Strain, %

(d)

Tenacity,gf/denier 2

0 0 0.5 1 1.5 2 2.5 3 Strain, %

(e)

Tenacity,gf/denier 2

0 0 0.5 1 1.5 2 2.5 3 Strain, %

(f)

Single fiber Single fiber

Yarb Yarn

Tenacity, gf/denier Tenacity, gf/denier Tenacity, Strain, % Strain, %

(a) (b)

4 Single fiber Single fiber 2 Yarn Yarn 0

0 1 2 3

Tenacity, gf/denier Tenacity, gf/denier Tenacity, Strain, % Strain, %

Single fiber Single fiber

Yarn Yarn

Tenacity, gf/denier Tenacity, gf/denier Tenacity, Strain, % Strain, %

(e) (f)

Figure 53 Comparison of the typical tensile behavior between the single fiber and yarn. (a) Spectra®, (b)

Vectran®, (c) Zylon®, (d) fiber glass with linear density 275 tex, (e) fiber glass with linear density 735

tex, (f) fiber glass with linear density 2400 tex.

Spectra Vectran Zylon Fiber Glass 275 tex

Tenacity, gf/denier Tenacity, Fiber Glass 735 tex Fiber Glass 2400 tex

Strain(%)

Figure 54 Typical tensile behavior of the yarns from high performance fibers

The tensile moduli of yarns are almost the same as single fibers except the fiber glass with 275 tex linear density. The Zylon® fiber has the highest tensile modulus, from the single fiber tensile modulus comparison, the yarn tensile modulus of fiber glass with 275 linear density is the highest among the fiber glass types, however, all e-glass fibers tensile moduli are much close to each other which can be noticed from the single fiber tensile modulus chart. Table 16 shows the comparison between the measured yarn tensile strength and yarn tensile strength data published by the manufactures. Spectra® fibers and Zylon® fibers have lower tested yarn tensile strength compared with the data from the manufacturers, which could be due to the effect of UV-Vis ray the yarns were subject to from production to test. Also, the measured yarn tensile strains are higher than the value provided by the manufactures. The individual observations of the testing results for all specimens are available in Tables F1-F6, Appendix F.

Table 16 Comparison of the high performance fibers yarn tensile properties

Avg. No. of Avg. Yarn Avg. Yarn Denier Break filaments Modulus Tenacity Yarns Strain

(denier) (%) (gf/denier) (gf/denier)

In this 1096.80(4 Spectra® 1300 240 5.8(16%) 32.43(6%) research %) s1000 Publisheda 1300 240 3.1 1200 38

In this Vectran® 1500 300 4.1(8%) 811.07(5%) 28.64(4%) research HT Publisheda 1500 300 3.8 800 30.0

In this 1349.42(2 Zylon® 1476 996 3.00(~0%) 31.37(4%) research %) HM Publisheda 1476 996 2.5 1800 42

In this 275 2475 378 2.4(22%) 322.45(3%) 7.05(9%) research tex Publisheda 2475 378 3.5 200-275 6.0-7.3

In this 735 6615 1960 2.6(19%) 316.97(3%) 7.02(6%) Fiber research Glass tex Publisheda 6615 1960 3.5 200-275 6.0-7.3

In this 2400 21600 3920 2.6(19%) 259.55(1%) 5.46(5%) research tex Publisheda 21600 3920 3.5 200-275 6.0-7.3

Number between “()” are CV, % a Typical properties of synthetic yarns-FIBERLINE

Table 17 shows Tukey multiple comparison ANOVA table for modulus of single fiber and yarns, Table 18 shows Tukey multiple comparison ANOVA table for tenacity of single fiber and yarns. The modulus and tenacity were normalized by the linear density of single fiber or yarn and the p values indicate if there were significant difference between the groups in 95% confidence level. From the p values in the table, it can be seen that there is no significant modulus difference between the single fiber and yarns of fiber glass. For polymeric fibers, it can be seen that there has no significant difference between Spectra® single fiber and

Vectran® single fiber, and Zylon® single fiber has the highest modulus when compared to them. For polymeric fiber yarns, there has significant difference between the modulus of different yarns which indicates Zylon® fiber yarns have the highest modulus. However, there is significant difference between the modulus of Spectra® single fiber and yarn as well as the Zylon® single fiber and yarn. No significant difference observed between the modulus of Vectran® single fiber and yarn which indicate the tensile strength of Vectran® single fiber can be well represented in Vectran® yarn.

Table 18 shows the tenacity comparison between the fibers and yarns. And the p values indicate that there is no significant difference between the single fiber tenacities of fiber glass with linear density of 2400 tex and 735 tex, and the single fiber tenacity of glass fiber with linear density of 275 tex is significantly different from other two fiber glass. For fiber glass yarns, no significant difference in tenacity observed between each other. For tenacity comparison between single fiber and yarn, p values indicate that there is significant difference in tenacity between the single fiber and yarn of fiber glass with linear density of 2400 tex as well as fiber glass with linear density of 735 tex. No significant difference in tenacity observed between the single fiber and yarn of fiber glass with linear density 275 tex. For polymeric fibers, the p values indicate no significant difference in tenacity observed between the Spectra® and Vectran® single fiber, and Zylon® single fiber has the highest tenacity. For yarns, the p values indicate no significant difference in tenacity observed between Spectra® and Zylon® yarn, and they have higher yarn tenacity than Vectran® yarn. For the comparison between the single fiber and yarn, Zylon® is the only one that has significant difference in tenacity observed between the single fiber and yarn. Overall, Zylon® single fiber and yarn have the best

93 performance in tensile properties. However, for both modulus and tenacity, Zylon® yarn have lower performance than single fiber which might indicate the number of filament has the effect on the yarn tensile properties represented from single fiber. Also, gauge length has the effect on the fiber and yarn tensile properties, as yarns have the larger gauge length during the tensile tests and higher possibility of flaws can be found on larger gauge length which can lower the yarn tensile performance.

Table 17 Tukey multiple comparison ANOVA table for modulus of single fiber and yarns. (a) and (b)

(S and Y are short for single fiber and yarn, respectively)

TYPE modulus LSMEAN LSMEAN Number 2400texS 334.78450 1 2400texY 259.55300 2 275texS 257.43421 3 275texY 322.44600 4 735texS 342.37632 5 735texY 316.97200 6 SpectraS 892.91550 7 SpectraY 1096.80200 8 VectranS 827.54900 9 VectranY 811.06900 10 ZylonS 1653.83763 11 ZylonY 1349.42100 12 (a)

Least Squares Means for effect TYPE Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: modulus i/j 1 2 3 4 5 6 7 8 9 10 11 12 1 0.1856 0.1004 0.8278 0.8714 0.7534 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 2 0.1856 0.9705 0.3374 0.1488 0.3810 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 3 0.1004 0.9705 0.2565 0.0750 0.2986 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 4 0.8278 0.3374 0.2565 0.7275 0.9334 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 5 0.8714 0.1488 0.0750 0.7275 0.6570 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 6 0.7534 0.3810 0.2986 0.9334 0.6570 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 7 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.0004 0.1591 0.1500 <.0001 <.0001 8 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.0004 <.0001 <.0001 <.0001 0.0002 9 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.1591 <.0001 0.7714 <.0001 <.0001 10 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.1500 <.0001 0.7714 <.0001 <.0001 11 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 12 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.0002 <.0001 <.0001 <.0001 (b)

Table 18 Tukey multiple comparison ANOVA table for tenacity of single fiber and yarns. (a) and (b)

(S and Y are short for single fiber and yarn, respectively)

TYPE tenacity LSMEAN LSMEAN Number 2400texS 9.7385000 1 2400texY 5.4580000 2 275texS 5.3778947 3 275texY 7.0500000 4 735texS 9.8747368 5 735texY 7.0150000 6 SpectraS 31.6195000 7 SpectraY 32.4280000 8 VectranS 30.5425000 9 VectranY 28.6410000 10 ZylonS 35.3365789 11 ZylonY 31.3730000 12 (a)

Least Squares Means for effect TYPE Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: tenacity i/j 1 2 3 4 5 6 7 8 9 10 11 12 1 0.0002 <.0001 0.0161 0.8818 0.0148 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 2 0.0002 0.9429 0.2143 0.0001 0.2245 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 3 <.0001 0.9429 0.1358 <.0001 0.1442 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 4 0.0161 0.2143 0.1358 0.0122 0.9782 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 5 0.8818 0.0001 <.0001 0.0122 0.0112 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 6 0.0148 0.2245 0.1442 0.9782 0.0112 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 7 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.4659 0.2348 0.0078 <.0001 0.8240 8 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.4659 0.0901 0.0034 0.0047 0.4100 9 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.2348 0.0901 0.0874 <.0001 0.4539 10 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.0078 0.0034 0.0874 <.0001 0.0338 11 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.0047 <.0001 <.0001 0.0001 12 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.8240 0.4100 0.4539 0.0338 0.0001 (b)

5.6 3D orthogonal woven preform reinforced composite mechanical properties

5.6.1 Tensile properties

For each type of high performance fibers, two panels of final composite materials were cut and conditioned in the tensile testing lab at least 24 hours before starting the testing. Five specimens from the first panel and six specimens from second panel were cut and tested for each high performance fiber. The composite tensile specimens of the first panel were tested without using the laser extensometer and the laser extensometer was used with the specimens of the second panel. Specimens for each type of high performance fibers were cut to test them in two directions: x- and y-directions. Preliminary tests were performed to find out suitable gripping pressure that is enough to prevent the slippage during the testing and avoid sample crushing at the jaws. The gripping pressure 13.5 Mpa was selected for most of the specimens and the specimen length was

150 mm and width was 30 mm for the specimens of panel 1, while specimens of 170 mm in length and 27 mm in width were used for panel 2. The thickness and width were recorded for all specimens. The composite tensile data of panel 2 for each type of high performance fibers were used to analyze the tensile properties of high performance fiber reinforced composite materials. Also, the gripping pressure and gripping distance for each specimen were recorded. The individual observations of composite specimens are reported in

Tables G1-3, Appendix G.

5.6.1.1 Tensile strength

Peak load is the highest applied load during a composite tensile test. In current research, the peak load for all specimens were recorded and normalized by the preform areal density and composite areal density to compare the reinforcement performance of each type of high performance fibers. The tenacity of composite was calculated with the peak load of composite tensile tests and the calculated theoretical fiber denier for corresponding specimen. The strain was obtained from the laser extensometer measurement. The load- strain and tenacity-strain curves were modified by using the trend line of original curves to give better

97 comparison between different specimens since the raw data was not smooth. Figure 55 shows the original load-strain curves.

Figure 55 Original load-strain curves.

Composite with Spectra® in x-direction 40000 35000 30000 1 25000 2 20000 3 Load,N 15000 4 10000 5 5000 6 0 0 1 2 3 4 5 Laser strain, %

(a)

Composite with Vectran® in x-direction 45000 40000 35000 30000 1 25000 2

20000 3 Load,N 15000 4 10000 5 5000 6 0 0 0.5 1 1.5 2 2.5 3 Strain, %

(b)

Composite with Zylon® in x-direction 60000

50000

40000 1 2 30000

3 Load,N 20000 4

10000 5 6 0 0.0 0.5 1.0 1.5 2.0 2.5 Strain, %

(c)

1 Composite with E-glass fiber in y-direction 2 40000 3 4 35000 5 30000 6 7 25000 8 20000 9

Load,N 10 15000 11 10000 12 13 5000 14 0 15 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 16 Strain, % 17

(d) Figure 56 shows the modified curves by using the trend line of each curves for composite specimens with difference high performance fibers and Figures 57-59 show the normalized load-strain curves that normalized by the preform areal density and composite areal density.

Figure 56 Modified load-strain curves

Composite with Spectra® in x-direction 40000 35000 30000 1 25000 2 20000 3 Load,N 15000 4 10000 5 5000 6 0 0 1 2 3 4 5 Strain, %

(a)

Composite with Vectran® in x-direction 45000 40000 35000 30000 1 25000 2

20000 3 Load,N 15000 4 10000 5 5000 6 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Strain, %

(b)

100

Composite with Zylon® in x-direction 60000

50000

40000 1 2 30000

3 Load,N 20000 4

10000 5 6 0 0.0 0.5 1.0 1.5 2.0 2.5 Strain, %

(c)

1 Composite with E-glass fiber in y-direction 2 3 50000 4 45000 5 40000 6 35000 7 30000 8 25000 9

Load,N 20000 10 15000 11 10000 12 5000 13 0 14 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 15 Strain, % 16 17

(d)

101

12 1 10 2 8 3 6

4 Load,N/(g/m2) 4 5

2 6

0 0 1 2 3 4 5 Strain, %

(a)

10 9 8 7 1 6 2 5 3 4 4 Load,N/(g/m2) 3 5 2 6 1 0 0 1 2 3 4 5 Strain, %

(b) Figure 57 Modified load-strain curves of composite with Spectra® in x-direction. (a) Load normalized by

preform areal density; (b) load normalized by composite areal density.

102

10 2 8 3

6 4 Load,N/(g/m2) 5 4 6 2

0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Strain, %

(a)

10 9 8 7 6 2 5 3 4 4

Load,N/(g/m2) 3 5 2 6 1 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Strain, %

(b) Figure 58 Modified load-strain curves of composite with Vectran® in x-direction. (a) Load normalized by

preform areal density; (b) load normalized by composite areal density.

103

1 15 2 3 10

4 Load,N/(g/m2) 5 5 6

0 0.0 0.5 1.0 1.5 2.0 2.5 Strain, %

(a)

12 1 10 2 8 3 6

4 Load,N/(g/m2) 4 5

2 6

0 0.0 0.5 1.0 1.5 2.0 2.5 Strain, %

(b) Figure 59 Modified load-strain curves of composite with Zylon® in x-direction. (a) Load normalized by

preform areal density; (b) load normalized by composite areal density.

Figure 60 shows the typical load-strain comparison curves and normalized curves and it indicates that composites with Zylon® in x-direction have the highest load either normalized by the preform areal density or composite areal density. Also, the composite specimens have the similar loading response behavior that indicated by that of single fiber.

104

Figure 60 Typical load-strain comparison curves. (a) Modified curves; (b) normalized by preform areal

density; (c) normalized by composite areal density.

60000

50000

40000

Spectra 30000

Vectran Load,N 20000 Zylon E-glass 2400 tex 10000

0 0 1 2 3 4 Strain, %

(a)

20 18 16 14 12 10 Spectra 8 Vectran

Load,N/(g/m2) 6 Zylon 4 2 0 0 1 2 3 4 Strain, %

(b)

105

8 Spectra 6 Vectran

Load,N/(g/m2) 4 Zylon

0 0 1 2 3 4 Strain, %

(c) Figure 61 shows the tenacity-strain curves for composite tensile specimens in x- and y-direction. Based on the single fiber and yarn tenacity-strain curves mentioned before, the tenacity-strain curves of composite tensile specimens with Spectra® and Vectran® fibers were modified by using the polynomial trend line.

While other such as composites tensile specimens with Zylon® fibers in x-direction and E-glass fibers in y-direction, their tenacity-strain curves were modified by using the linear trend line.

106

Figure 61 Tenacity-strain curves for composite tensile specimens in x- and y-direction. (a) Spectra®; (b)

Vectran®; (c) Zylon®; (d) E-glass fiber

20 1 2 15 3

10 4 Tenacity,gf/denier 5 5 6

0 0 1 2 3 4 5 Strain, %

(a)

1 15 2 3 10 4

Tenacity,gf/denier 5 5 6

0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Strain, %

(b)

107

25 1 20 2

15 3 4

Tenacity,gf/denier 10 5 5 6

0 0.0 0.5 1.0 1.5 2.0 2.5 Strain, %

(c)

12.00

10.00

8.00

6.00

4.00 Tenacity. gf/denier

2.00

0.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Strain, %

(d)

Figure 62 shows the typical tenacity-strain curves for composite tensile specimens with Spectra®,

Vectran® and Zylon® fibers in x-direction and E-glass fibers in y-direction. From Figure 62, composite tensile specimens with Zylon® fibers in their x-direction have the highest tenacity which is in agreement with the results of single fiber tensile tenacity results.

108

Spectra 15 Vectran

10 Zylon Tenacity,gf/denier E-glass 2400 tex 5

0 0 1 2 3 4 Strain, %

Figure 62 Typical tenacity-strain curves for specimens with different high performance fibers in x-

direction and E-glass fibers in y-direction.

Table 19 shows the tenacity comparison table for each type of high performance fibers in different forms.

For polymeric fibers, the tenacity results have the same indication which is Zylon® fibers have the highest tenacity in different forms when compared with other high performance fibers. From these results, Spectra® yarns have the higher tenacity than its other forms. For other fibers, their tenacities are sequentially reduced in different forms from single fiber to composite.

109

Table 19 Tenacity comparison.

Average Tenacity Type gf/denier Spectra 31.62 Vectran 30.54 Zylon 35.34 Single Fiber glass 275 tex 5.38 Fiber glass 735 tex 9.87 Fiber glass 2400 tex 9.74 Spectra 32.43 Vectran 28.64 Zylon 31.37 Yarn Fiber glass 275 tex 7.05 Fiber glass 735 tex 7.02 Fiber glass 2400 tex 5.46 x-direction Spectra 23.58 x-direction Vectran 21.34 Composite x-direction Zylon 27.68 Fiber glass 2400 tex 8.05

Figures 63-65 show the tenacity comparison between the different forms of high performance fibers. Figure

63 shows that Spectra® and e-glass fiber of 275 tex have higher tenacity than their single fibers. And

Spectra yarn has the highest yarn tenacity than other high performance fibers, but the tenacity difference between Spectra and Zylon yarn is not significant which indicated by previous Tukey multiple comparison.

However, Figure 64 and Figure 65 show the tenacity values of e-glass fibers of 2400 tex are closest to 45 degree straight line which indicate that its single fiber tensile tenacity can well represent the tensile tenacity of their composites.

110

30 Spectra 25 Vectran 20 Zylon 15 Fiber glass 275tex

10 Fiber glass 735tex YarnTenacity, gf/denier 5 Fiber glass 2400tex

0 0 5 10 15 20 25 30 35 40 Single Fiber Tenacity, gf/denier

Figure 63 Tenacity comparison between the single fiber and Yarn.

25 Spectra 20 Vectran 15 Zylon 10 Fiber glass 2400tex

Composite Composite Tenacity,gf/denier 5

0 0 5 10 15 20 25 30 35 40 Single Fiber Tenacity, gf/denier

Figure 64 Tenacity comparison between the single fiber and corresponding composites.

111

20 Spectra

15 Vectran Zylon 10 Fiber glass 2400tex

Composite Composite Tenacity,gf/denier 5

0 0 5 10 15 20 25 30 35 Yarn Tenacity, gf/denier

Figure 65 Tenacity comparison between the yarn and corresponding composites.

112

5.6.1.2 Peak Stress

Figure 66 shows the stress-strain curves for composite specimens with different type of high performance fibers and the curves were modified to indicate better stress behavior than original curves. Figure 66 indicates that, for composite specimens with different type of high performance fibers in x-direction stress response behavior is similar to the tensile tenacity behavior of their single fiber. The individual specimens of composite with Spectra® fibers and Vectran® in x-direction have almost same trend.

Figure 66 Modified stress-strain curves for composite specimens with difference high performance fibers.

(a) specimens with Spectra® in x-direction; (b) specimens with Vectran® in x-direction; (c) specimens

with Zylon® in x-direction; (d) specimens with E-glass fiber in y-direction.

600

500

400 1 2 300 3

Stress, Stress, Mpa 200 4 5 100 6

0 0 1 2 3 4 5 Strain, %

(a)

113

600

500

400 1 2 300 3

Stress, Stress, Mpa 200 4 5 100 6

0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Strain, %

(b)

1000 900 800 700 1 600 2 500 3 400 Stress, Stress, Mpa 4 300 5 200 6 100 0 0.0 0.5 1.0 1.5 2.0 2.5 Strain, %

(c)

114

600.00 1 2 3 500.00 4 5 400.00 6 7 300.00 8 9 Stress, Stress, Mpa 200.00 10 11 100.00 12 13 0.00 14 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 15 Strain, % 16 17

(d)

Figure 67 shows the peak stress for composite tensile test specimens with different type of high performance fibers. It can be seen that composite tensile specimens with Zylon® fibers in x-direction have highest tensile stress than other high performance fibers. The composite tensile specimens with Spectra® fibers and

Vectran® fibers have almost the same peak stress, however, from the filling yarn densities and fiber volume, composite tensile specimens with Spectra® fibers have weight saving advantage than tensile specimens with Vectran® fibers even they have the close tensile stress performance (see the preform areal density and composite areal density is available in section 4.2.5 and 4.2.6.)

For y-direction, as the specimens have the same high performance fiber, which is fiber glass in y-direction, the specimens have almost the same tensile stress performance according to the Figure 67.

115

900.00

800.00

700.00

600.00

500.00

400.00

Peak Stress, Peak Stress, Mpa 300.00

200.00

100.00

0.00 Spectra Vectran Zylon Fiber glass, Ince

(a)

900.00

800.00

700.00

600.00

500.00

400.00

Peak Stress, Peak Stress, Mpa 300.00

200.00

100.00

0.00 Spectra Vectran Zylon Fiber glass, Ince

(b)

Figure 67 Average peak stress for each type of high performance fibers in x-direction (a) and y-direction

(b)

116

Table 20 shows the Tukey multiple comparison ANOVA table for peak stress in x-direction. From the p values, there no significant difference in stress between composites reinforced with Spectra® and Vectran® in x-direction. Composites reinforced with Zylon® fibers have the highest peak stress in x-direction.

Table 20 Tukey multiple comparison ANOVA table for peak stress in x-direction. (a) and (b)

type xstress LSMEAN LSMEAN Number Spectra 458.256462 1 Vectran 475.675683 2 Zylon 789.605120 3 (a)

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: xstress i/j 1 2 3 1 0.5117 <.0001 2 0.5117 <.0001 3 <.0001 <.0001 (b) Table 21 shows the comparison ANOVA table for peak stress in y-direction, this comparison is between the peak stress in y-direction in this research and the peak stress in y-direction taken from [44]. It should be noted that data reported in the table is for 3 layers. The p value indicate that no significant difference observed between the peak stresses in y-direction of both experiments.

Table 21 Tukey multiple comparison ANOVA table for peak stress in y-direction.

H0:LSMean1=LSMean2 type ystress LSMEAN Pr > |t| Current 413.527444 0.6448 [44] 425.770000

117

For better understanding of tensile stress performance of specimens with difference type of high performance fibers, the stress-strain curves were normalized by the preform areal density and composite areal density which can give more detailed composite tensile performance such as the specific stress related to the weight and weight saving consideration. Figures 68-70 show the normalized stress-strain curves for difference specimens.

118

0.25

0.20

1 0.15 2 3 0.10 4

Stress, Stress, Mpa/(g/m2) 5 0.05 6

0.00 0 1 2 3 4 5 Strain, %

(a)

0.16

0.14

0.12 1 0.10 2 0.08 3 0.06 4

Stress, Stress, Mpa/(g/m2) 0.04 5

0.02 6

0.00 0 1 2 3 4 5 Strain, %

(b) Figure 68 Normalized stress-strain curves for specimens with Spectra® in x-direction. (a) Normalized by

preform areal density; (b) normalized by composite areal density.

119

0.2 0.18 0.16 0.14 0.12 2 0.1 3 0.08 4

0.06 5 Stress, Stress, Mpa/(g/m2) 0.04 6 0.02 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Strain, %

(a)

0.14

0.12

0.1 2 0.08 3 0.06 4

0.04 5 Stress, Stress, Mpa/(g/m2) 6 0.02

0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Strain, %

(b)

Figure 69 Normalized stress-strain curves for specimens with Vectran® in x-direction. (a) Normalized by

preform areal density; (b) normalized by composite areal density.

120

0.35

0.3

0.25 1 0.2 2

0.15 3 4 0.1 Stress, Stress, Mpa/(g/m2) 5 0.05 6

0 0.0 0.5 1.0 1.5 2.0 2.5 Strain, %

(a)

0.25

0.2

1 0.15 2 3 0.1 4

Stress, Stress, Mpa/(g/m2) 5 0.05 6

0 0.0 0.5 1.0 1.5 2.0 2.5 Strain, %

(b)

Figure 70 Normalized stress-strain curves for specimens with Zylon® in x-direction. (a) Normalized by

preform areal density; (b) normalized by composite areal density.

Figure 71 shows the typical stress-strain curves for the comparison between the typical stress-strain curves normalized by the preform areal density and composite areal density. From Figure 71, composite specimens with Zylon® fibers in their x-direction have the outstanding normalized tensile stress performance which is complying with the single fiber tenacity and composite tenacity results.

121

Figure 71 Typical stress-strain comparison and normalized stress-strain curves. (a) Stress-strain curves;

(b) stress-strain curves normalized by preform areal density; (c) stress-strain curves normalized by

composite areal density.

900 800 700 600

500 Spectra 400 Vectran

Stress, Stress, Mpa 300 Zylon 200 E-glass 2400 tex 100 0 0 1 2 3 4 Strain, %

(a)

0.35

0.30

0.25

0.20 Spectra 0.15 Vectran

0.10 Zylon Stress, Stress, Mpa/(g/m2)

0.05

0.00 0 1 2 3 4 Strain, %

(b)

122

0.25

0.20

0.15 Spectra 0.10 Vectran

Zylon Stress, Stress, Mpa/(g/m2) 0.05

0.00 0 1 2 3 4 Strain, %

The tensile strain of the composite materials was measured with extensometer. Figure 72 shows the strain comparison between the strain results in x-direction for polymeric fibers and y-direction for e-glass fibers of 2400 tex. Figure 72(a) shows that composite materials have different strains as three different high performance fibers were used in x-direction and composite specimens have different tensile strain to reflect their single fiber or yarn strains. For y-direction, the composite materials have very similar strain which is expected since the fibers in the y-direction are only one type of fiber glass as indicated in the experimental section. However, as the composite strain were measured with laser extensometer and no extensometer was used to measure the tensile strains of single fiber and yarn which can lead to differences between the strains of high performance fibers in different forms. It is apparent from the results that fiber slippage from clamps took place during single fiber testing and the significant variation (see error bar) support this fact.

123

18.00

16.00

14.00

12.00

10.00 composite

8.00 single fiber Strain,% Yarn 6.00

4.00

2.00

0.00 Spectra Vectran Zylon

(a)

4.50

4.00

3.50

3.00

2.50

2.00 Strain,% 1.50

1.00

0.50

0.00 Composite Single fiber Yarn

(b)

Figure 72 Composite strains for composites with different type of high performance fibers. (a) x-direction

for polymeric fibers; (b) E-glass fiber

124

5.6.1.4 Tensile break energy

From the Load-Extension tensile curves, the break energy for each type of fibers, yarns and composites can be calculated and normalized by the fiber linear density and gauge length. Figure 73 shows the relationship between the normalized yarn break energy and normalized single fiber break energy for each type of high performance fibers. It indicates that Spectra® fiber has the highest single fiber tensile break energy and highest yarn tensile break energy, however, the single fiber break energy is extremely higher than the yarn break energy and this is due to the high tensile break strain of Spectra® single fiber. For other 5 high performance fibers, the single fiber break energy and yarn break energy are close. Figure 74 shows the relationship between the normalized composite tensile break energy in x-direction and normalized single fiber tensile break energy. The composite specimens with Spectra® fiber in x-direction have the highest normalized tensile break energy while the composite break energy and single fiber energy of other type of high performance fibers are very close to the 45° line.

Figure 75 shows the relationship between the normalized composite tensile break energy and normalized yarn tensile break energy of high performance fibers. The figure indicates that for each type of the high performance fibers, the composite break energy are close to the corresponding yarns’ break energy. From both Figure 74 and Figure 75 the composites with Vectran®, Zylon® fiber reinforced in x-direction and E- glass fiber in y-direction, the break energy is highly correlated with the corresponding fiber or yarn break energy. These correlations are very useful when designing composite parts with required performance specifications.

125

3.5

3.0

2.5 Spectra 2.0 Vectran

1.5 Zylon Fiber glass 275tex 1.0 Fiber glass 735tex

YarnBreak Energy,J/denier 0.5 Fiber glass 2400tex

0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Single Fiber Break Energy, J/denier

Figure 73 Break energy comparison between the single fiber and yarn.

3.5

3.0

2.5

2.0 Spectra

1.5 Vectran Zylon 1.0 Fiber glass 2400tex

0.5 Composite Composite Energy, Break J/denier 0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Single Fiber Break Energy, J/denier

Figure 74 Break energy comparison between the single fiber and corresponding composites.

126

1.50

1.25

1.00

Spectra 0.75 Vectran

0.50 Zylon Fiber glass 2400tex

0.25 Composite Composite Energy, Break J/denier 0.00 0.00 0.25 0.50 0.75 1.00 1.25 1.50 Yarn Break Energy, J/denier

Figure 75 Break energy comparison between the yarn and corresponding composites.

127

Figure 76 shows the broken specimen in Y-direction. However, for the specimens with different type of high performance fiber in this research, the tensile specimens were suffering the same damage in clamping area, which indicated by the red circle, for both X- and Y-directions. Possible reasons include: 1) void existing inside the composite, 2) composites had poor curing after the infusion procedure and 3) the three high performance polymer fibers have relatively low compressive strength, fiber glass are isotropic material while other high performance polymeric fibers have poor transverse compression resistance.

Figure 76 Broken composite tensile specimen in Y-direction.

5.6.2 Composite material Dynatup impact testing

The Tup impact testing is conducted to follow the ASTM D3763. The specimens’ size was 66 mm by 66 mm to meet the ASTM and testing machine holder size. The preliminary tests indicate that the striker with total weight 4.92 kg is not capable to penetrate the specimens with Spectra® and Zylon®, while the specimen with Vectran® was totally penetrated. Figure 77 shows the specimens after the preliminary tests.

Additional 5 kg weight was added to be able to penetrate all the specimens.

128

(a) (b) (c)

Figure 77 Specimens after preliminary Dynatup impact tests. (a) Spectra® in X-direction; (b) Vectran® in

X-direction; (c) Zylon® in X-direction.

The Force-Displacement curves of individual specimens for each type of high performance fibers are presented in the Figure 78. In order to compare the penetrating force and energy between different types of fibers, the force was normalized by each specimen’s thickness, average preform areal density and composite areal density. The normalization using areal densities was done since previous research indicated that the

3D woven composite panel thickness and areal density is decreasing from the inlet to outlet, and the composite panel’s fiber volume fraction is increasing from the inlet to the outlet [44]. The individual observations and other details of the testing results for all specimens are reported in Table H1-6, Appendix

The composite areal density was determined by measuring the Tup impact specimens’ areal density and average 3D orthogonal preform areal density was calculated as indicated in section 4.2.5.

129

Figure 78 Force-displacement curves for each type of high performance fibers. (a) Spectra®; (b)

Vectran®; (c) Zylon®.

(a)

(b)

130

(c)

Figure 79 Force-displacement curves for each type of high performance fibers normalized with composite

thickness. (a) Spectra®; (b) Vectran®; (c) Zylon®.

(a)

131

(b)

(c)

132

Figures 79-81 show the Force-Displacement curves of individual specimens for each type of high performance fibers, the force was normalized by the thickness of specimens, average 3D orthogonal preform areal density and composite areal density, respectively. When compared to specimens with

Spectra® and Vectran®, specimens with Zylon® have the relative high normalized forces in the three cases which indicate specimens with Zylon® can provide better puncture impact resistance. Vectran® specimens exhibited the lowest resistance to puncture impact. From the fiber strength results, the rank of fibers from highest to lowest is Zylon®, Spectra®, and Vectran®. This is the same rank as the single fiber strength results.

Figure 80 Force-Displacement curves of individual specimen for each type of high performance fibers

normalized with 3D orthogonal preform areal density. (a) Spectra®; (b) Vectran®; (c) Zylon®.

(a)

133

(b)

(c)

134

Figure 81 Force-Displacement curves of individual specimen for each type of high performance fibers

normalized with composite areal density. (a) Spectra®; (b) Vectran®; (c) Zylon®.

(a)

(b)

135

(c)

136

Figure 82 shows the energy needed to perforate specimens in Tup impact mode, and specimens with

Zylon® as the filling yarns in x-direction have relative high penetrating energy when compared with other two types of composite specimens. To nullify the effect in variation of the composite structures, the results of Figure 82 were normalized by thickness, preform areal density and composite areal density as seen in

Figures 83-85, respectively. The results indicate specimens with Zylon® have excellent high perforating energy of Tup impact test that lead to the conclusion that composites with Zylon® fibers in x-direction improved puncture impact resistance of their composites compared to those made from Spectra® and

Vectran®. Composites from Vectran® fibers in x-direction exhibited the lowest penetrating energy. Again, the normalized puncture resistance energy of the three types of composites reflect the fiber properties.

Figure 82 Energy-Displacement curves of individual specimen for each type of high performance fibers.

(a) Spectra®; (b) Vectran®; (c) Zylon®.

(a)

137

(b)

(c)

138

Figure 83 Energy-Displacement curves of individual specimens for each type of high performance fibers

normalized with composite thickness. (a) Spectra®; (b) Vectran®; (c) Zylon®.

(a)

(b)

139

normalized with preform areal density. (a) Spectra®; (b) Vectran®; (c) Zylon®.

(a)

140

(b)

(c)

141

Figure 85 Energy-Displacement curves of individual specimens for each type of high performance fibers

normalized with composite areal density. (a) Spectra®; (b) Vectran®; (c) Zylon®.

(a)

(b)

142

(c)

143

Table 22 shows that p values of Tukey multiple comparison for peak force (normalized by composite areal density) between the composites reinforced with difference type of high performance fibers in x-direction.

The composite reinforced with Zylon® fibers has the highest normalized peak force and the composite with

Vectran® fibers have the lowest normalized peak force.

Table 22 Tukey multiple comparison ANOVA table for peak force normalized with composite areal

density. (a) and (b).

Type Peakforce LSMEAN LSMEAN Number Spectra 1.91520222 1 Vectran 1.71273257 2 Zylon 2.43795231 3 (a)

Least Squares Means for effect Type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: Peakforce i/j 1 2 3 1 0.0268 <.0001 2 0.0268 <.0001 3 <.0001 <.0001 (b)

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Table 23 shows the multiple comparison ANOVA table for perforation energy normalized with composite areal density. The p values indicate significant difference observed between the energy normalized by the composite areal densities. Composites with Zylon fibers in x-direction have the highest perforating energy and composites with Vectran fiber have the lowest perforating energy.

Table 23 Tukey multiple comparison ANOVA table for energy normalized with composite areal density.

(a) and (b)

Type energy LSMEAN LSMEAN Number Spectra 0.01269557 1 Vectran 0.01075956 2 Zylon 0.01761135 3 (a)

Least Squares Means for effect Type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: energy i/j 1 2 3 1 <.0001 <.0001 2 <.0001 <.0001 3 <.0001 <.0001

(b)

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The graphs in the Figure 86 depict typical puncture force-displacement relationship for each type of high performance fibers. It is clear from the figure that the composite materials from Zylon fibers in x-direction show the highest peak puncture force which indicated by the Tukey comparison table. Table 24 and Table

25 show the summary of the normalized peak force and energy including number of specimens tested for each fiber type, the peak force are normalized by the composite thickness, preform areal densities and composite areal densities.

Table 24 Summary Dynatup impact results with peak force normalized

Normalized Peak Force Peak Thickness Type No. of Force Preform Composite Specimens Thickness areal areal density density mm N N/mm N/(g/m2) N/(g/m2) Spectra 11 2.687 7291.948 2711.86 2.853 1.915 Vectran 10 2.854 7534.77 2640.92 2.725 1.713 Zylon 10 2.372 9691.70 4096.43 3.475 2.438

Table 25 Summary Dynatup impact results with energy normalized.

Normalized Energy

Thickness Energy Type No. of Preform Composite Specimens Thickness areal areal density density mm J J/mm J/(g/m2) J/(g/m2) Spectra 11 2.687 48.292 18.12 0.0189 0.0127 Vectran 10 2.854 47.32 16.59 0.017 0.011 Zylon 10 2.372 70.08 29.64 0.025 0.018

Figure 87 shows typical force-displacement curves normalized by the composite thickness, 3D orthogonal woven preform areal density and composite areal density for each type of high performance fibers. The

146 composite material with Spectra® fibers as the x-direction have highest displacement and from the single fiber tensile testing results, the yarn tensile testing results, both of the tensile testing results indicate that the

Spectra® fibers have the highest strain. Also, the figure indicates composite specimens with Zylon® in x- direction have the highest peak force when compared with specimens from the other two fibers. The details of the individual specimens’ results for each type of high performance fibers are available in Appendix H.

Figure 86 Typical Force-Displacement curves for composite with each type of high performance fiber

147

Figure 87 Typical normalized Force-Displacement curves for composite with each type of high performance fiber. (a) Peak force normalization with thickness; (b) peak force normalization with 3D

orthogonal preform areal density; (c) peak force normalization with composite areal density.

(a)

(b)

148

(c)

Figure 88 shows typical Energy-Displacement curves for composite from each type of high performance fibers and Figure 89 shows typical curves of energy-displacement relationships normalized by the specimens’ thickness, 3D orthogonal preform areal density and composite specimen areal density. Both figures indicate that specimens with Zylon® show the highest perforating energy. The results of peak puncture resistance force, normalized puncture force, energy and normalized energy are consistent and reflect fiber tensile properties. Zylon® exhibited the highest value followed by Spectra®, then Vectran®.

149

Figure 88 Typical Energy-Displacement curve for composite with each type of high performance fibers

(a)

150

(b)

(c)

Figure 89 Typical normalized Energy-Displacement curves for composite with each type of high performance fiber. (a) Energy normalization by thickness; (b) energy normalization by 3D orthogonal

preform areal density; (c) energy normalization by composite areal density.

151

Figure 90 shows the specimens reinforced by Spectra in x-direction after the Tup impact and they indicate that the impact damage was located in a small area on the specimen and unlike the laminated composites mentioned in literature review section, no delamination was observed which is contributed to the z-yarns in through thickness direction. This was observed for Tup impact specimens.

(a)

(b)

Figure 90 Tup specimens of composite reinforced by Spectra in x-direction. (a) Top view; (b) side view.

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5.6.3 Charpy Impact testing results

The specimens were conditioned in the tester location at least 24 hours before testing in the testing room that is conditioned with temperature of 22°C and the relative humidity of 55%. According to the ASTM standards, the specimen size should be 12.7 mm in width and 63.5 mm in length. However, the diamond blade cutter available is a manual cutter and it is difficult to control cutting the specimens in such small width dimensions. For this research, the width of each specimen was measured and recorded. Two break types were observed and recorded in this testing. No specific break types are provided by the ASTM standard. The observed break types are Non-break and Partial break for the composite materials studied as defined in the Izod impact test section (table 29). Figure 91 shows the specimens before and after the Charpy

Impact testing for x- and y-directions that indicate the two broken types for all specimens in x- and y- direction. The details of individual specimen for each type of high performance fibers are available in

Tables I1-6, Appendix I.

Figure 91 The pictures of composite specimens for Charpy Impact. (a) y-direction; (b) x-direction

(a)

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(b) Table 26 shows the details of the Charpy Impact testing results. From the results, the composite materials with Vectran® as the x-direction yarns have the highest impact resistance (REL) which is the energy normalized by the specimen thickness and highest impact strength (RE) which is the energy normalized by the specimen cross-section area.

Equation (15) and (16) below were used to calculate the REL and RE values for Charpy impact test.

Equation (17) was used to calculate the energy absolved percent.

퐸 푅퐸퐿 = (15) 푡

퐸 푅퐸 = (16) 푡·푤 Where E is energy, t is specimen’s thickness and w is the specimen’s width.

퐸 푃퐸 = (17) 퐸ℎ

Where PE is the absolved energy percent, E is the result energy and Eh is the total hammer energy.

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Table 26 The Charpy Impact testing results for each type of high performance fibers in X direction and Y

direction. (a) Specimens in Y direction; (b) specimens in X direction.

Avg. Avg. Avg. Avg. Avg. Absolved Fiber Thickness Width Result REL RE Energy (mm) (mm) Energy(J) (J/m) (KJ/m2) Percent (%) Y Direction Spectra® 2.851 13.655 7.582 2686.265 197.592 35.091 Vectran® 2.947 13.790 11.524 3925.609 286.252 53.340

Zylon® 2.606 13.634 9.586 3717.503 272.345 44.368

(a)

Avg. Avg. Avg. Avg. Absolved Result Avg. RE Energy Fiber Thickness Width REL Energy(J (kJ/m2) Percent (mm) (mm) ) (J/m) (%) X Direction Spectra® 2.593 13.318 6.409 2469.218 185.257 29.664

Vectran® 2.851 13.373 10.393 3699.044 276.521 48.106

Zylon® 2.390 13.572 7.252 3009.150 221.853 33.566

(b)

From the tested specimens, the specimens in x-direction for all high performance fibers have the Non-break type, which indicate that the fibers in x-direction are not broken during the testing. The specimens in y- direction have the partial break type as the fiber glass were mostly broken in the testing, however, the fibers in x-direction have the ability to stop the tested specimens break apart as the fibers in x-direction were not broken. From the test results, specimens in y-direction have higher impact resistance when compared with their counterpart specimens in x-direction. And composite specimens with Vectran® fibers in x-direction have the highest Charpy impact resistance when compared with composite specimens with other two high performance fibers; Spectra® and Zylon®. When testing the specimens in x-direction, if the resin is the only material failed during the testing, then the impact resistance results for each type of high performance should be close to each other, however, the testing result is not indicating this and specimens with Vectran® fibers in x-direction have relatively higher impact resistance than other two high performance fibers.

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Table 27 shows the Tukey multiple comparison ANOVA table for Charpy impact resistance in x- and y- direction. The p values indicate composite reinforced by Vectran® fibers in x-direction have the highest

Charpy impact resistance, and no significant difference observed in Charpy impact resistance between the composites reinforced by Spectra and Zylon® fibers. For y-direction, no significant difference observed between the Charpy impact resistance of composites reinforced by Vectran and Zylon® fibers, and composite reinforced by Spectra® fibers have the lowest Charpy impact resistance. And composites reinforced by Vectran fibers have the best Charpy impact test performance in both x- and y-direction.

Table 27 Tukey multiple comparison ANOVA table for Charpy impact resistance (REL) in x- and y-

direction. (a) and (b)

type REL LSMEAN LSMEAN Number SpectraX 2469.21849 1 SpectraY 2686.26463 2 VectranX 3699.04408 3 VectranY 3925.60911 4 ZylonX 3009.15021 5 ZylonY 3717.50329 6 (a)

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: REL i/j 1 2 3 4 5 6 1 0.4796 0.0004 <.0001 0.1003 0.0005 2 0.4796 0.0024 0.0003 0.3182 0.0030 3 0.0004 0.0024 0.4607 0.0385 0.9541 4 <.0001 0.0003 0.4607 0.0075 0.5178 5 0.1003 0.3182 0.0385 0.0075 0.0417 6 0.0005 0.0030 0.9541 0.5178 0.0417 (b)

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Table 28 shows the multiple comparison ANOVA table for Charpy impact strength in x- and y-direction.

The p values indicate composite reinforced by Vectran fibers have the highest Charpy impact strength in x-direction. And no significant difference observed between the impact strength of composite reinforced by Vectran and Zylon fibers in y-direction, which fiber glass is the major load carrier in y-direction.

Additional Tukey multiple comparison analyses were conducted to separate the test direction results. Tables

I.7-I.10, Appendix I show the results. In general, the results are same as combining the x- and y-direction in the analyses. The exception is that the Zylon Charpy impact resistance in x-direction (REL and RE) is significantly higher than the Spectra fibers. This reflect the difference in fiber and yarn strength of both fibers.

Table 28 Tukey multiple comparison ANOVA table for Charpy impact strength (RE) in x- and y-

direction. (a) and (b)

type RE LSMEAN LSMEAN Number SpectraX 185.256747 1 SpectraY 197.595939 2 VectranX 276.521175 3 VectranY 286.251877 4 ZylonX 221.853080 5 ZylonY 272.345103 6 (a)

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Table 28 Continued

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: RE i/j 1 2 3 4 5 6 1 0.5943 0.0004 0.0001 0.1389 0.0011 2 0.5943 0.0018 0.0006 0.3212 0.0043 3 0.0004 0.0018 0.6742 0.0307 0.8632 4 0.0001 0.0006 0.6742 0.0122 0.5673 5 0.1389 0.3212 0.0307 0.0122 0.0539 6 0.0011 0.0043 0.8632 0.5673 0.0539

(b)

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5.6.4 Composite material Izod Impact testing results

Specimens were conditioned in the tester location for at least 24 hours at room temperature of 22°C and humidity of 55%. According to the ASTM standard, the specimen size should be 12.7 mm width and 127 mm length, which is difficult to cut the specimens with exact width by using the cutter available as indicated above. The specimens of panel 2 were used to analyze the Izod impact strength for composites reinforced of difference type of high performance fibers and the width and thickness dimensions for each specimen were recorded. Table 29 indicates the break types for Izod impact testing according to ASTM D256.

Table 29 Break types for Izod impact test

Break Type List

C Complete Break – A break where the specimen separate into two or more pieces

Hinge Break – An incomplete break, such that one part of the specimen cannot support itself H above the horizontal when the other part is held vertically (less than 90° included angle)

Partial Break – An incomplete break that does not meet the definition for a hinge break but P has fractured at least 90% of the distance between the vertex of the notch and the opposite side

Non-Break – An incomplete break where the fracture extends less than 90% of the distance NB between the vertex of the notch and the opposite side

In this research, two types of break were observed and they are Hinge break (H) and Non-break (NB). The specimens in x-direction give NB type break and those in y-direction showed H type break. Figure 92 shows the specimens after the impact testing and two types of specimen breakage were observed for all composite specimens. For each type of high performance fibers, specimens in y-direction have the H break type and the reason is the fibers in y-yarns are almost all broken during the impact testing and the fibers in x-yarn and x-direction provide support to stop the specimen break into two separate parts. The NB type break can

159 be observed in all specimens in x-direction, the reason for this phenomenon is the Izod impact hammer is not breaking the fibers in x-direction, which can provide the strength to prevent the specimens break into separate parts even though the resin was broken. Additional testing was conducted by using highest energy hammer available to find out whether the composite specimen break into separate parts. It was found that these two types of break are still observed in relative directions. The fibers or yarns in x-direction were not broken, while the cured resin was completely damaged and the glass fibers yarns in y-direction provide the impact strength to the composite specimens in y-direction. Table 30 summarizes the Izod impact testing results for each type of high performance fibers in x- and y-direction. The details of individual specimen for each type of high performance fibers are available in Tables J1-6, Appendix J.

160

(a)

(b) Figure 92 Specimens of composites reinforced by Vectran in x-direction for Izod impact tests. (a) x-

direction; (b) y-direction.

161

Table 30 The Izod impact testing results for each type of high performance fibers in different directions.

Avg. Avg. Average Average Average Filling Fiber Thickness Width Result REL RE Direction (mm) (mm) Energy(J) (J/m) (J/m2)

Spectra® 2.689 12.832 8.550 3142.590 245.222 x- Vectran® 2.849 13.732 11.361 3985.244 289.877 Direction Zylon® 2.468 13.238 10.016 4046.446 306.670

Spectra® 2.707 12.893 9.365 3447.651 269.237 y- Vectran® 2.905 13.550 10.497 3604.679 265.423 Direction Zylon® 2.451 13.980 9.772 3950.623 282.529

From Table 30, for both x- and y-direction specimens, Zylon® has the highest average impact resistance

(REL) and the highest average impact strength (RE). When comparing the specimens between the x- and y-direction, the specimens in x-direction have higher impact resistance and impact strength than that of specimens in y-direction except the Spectra® which indicates that unlike Charpy impact test, specimens in x-direction tend to have higher Izod impact resistance than their counterpart specimens in x-direction for specimens with Vectran® fibers and Zylon® fibers. This also indicate that Vectran® fibers and Zylon® fibers tend to provide Izod impact strength to the composite specimens in x-direction.

The impact resistance (REL) and impact strength (RE) were calculated by using equations (16) and (17).

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Table 31 shows the Tukey multiple comparison ANOVA table for Izod impact resistance in x- and y- direction. The p values indicate no significant difference observed between the Izod impact resistance of composites reinforced of each type of high performance fiber in x-direction as well as the result in y- direction at 95% confidence level.

Table 31 Tukey multiple comparison ANOVA table for Izod impact resistance (REL) in x- and y-

direction.

type REL LSMEAN LSMEAN Number SpectraX 3142.66667 1 SpectraY 3447.65143 2 VectranX 3985.24434 3 VectranY 3604.67914 4 ZylonX 4046.44626 5 ZylonY 3950.62277 6 (a)

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: REL i/j 1 2 3 4 5 6 1 0.5035 0.0712 0.3132 0.0539 0.0829 2 0.5035 0.2420 0.7298 0.1938 0.2730 3 0.0712 0.2420 0.4049 0.8928 0.9392 4 0.3132 0.7298 0.4049 0.3346 0.4485 5 0.0539 0.1938 0.8928 0.3346 0.8330 6 0.0829 0.2730 0.9392 0.4485 0.8330 (b)

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Table 32 shows the Tukey multiple comparison ANOVA table for Izod impact strength in x- and y- direction. The p values indicate no significant between the results in both x- and y-direction.

Table 32 Tukey multiple comparison ANOVA table for Izod impact strength (RE) in x- and y-direction.

type RE LSMEAN LSMEAN Number SpectraX 245.333333 1 SpectraY 269.236958 2 VectranX 289.876815 3 VectranY 265.422804 4 ZylonX 306.669827 5 ZylonY 282.529466 6 (a)

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: RE i/j 1 2 3 4 5 6 1 0.4832 0.1958 0.5552 0.0784 0.2780 2 0.4832 0.5444 0.9105 0.2750 0.6957 3 0.1958 0.5444 0.4732 0.6215 0.8287 4 0.5552 0.9105 0.4732 0.2300 0.6151 5 0.0784 0.2750 0.6215 0.2300 0.4789 6 0.2780 0.6957 0.8287 0.6151 0.4789 (b)

Additional Tukey multiple comparison analyses were conducted to separate the test direction results. Tables

J.7-J.10, Appendix j show the results. In general, the results are same as combining the x- and y-direction in the analyses. The exception is that the Zylon Izod impact resistance in x-direction (REL) is significantly higher than the Spectra and Vectran fibers. Additionally, the Zylon impact strength (RE) is significantly higher than Spectra. This reflect the differences in fiber and yarn strength of the three fibers.

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6. Conclusion and recommendation for future studies

The single filament tensile properties of four high performance fibers were tested and their yarn tensile properties were also tested to help in understanding how the single filament tensile strength represented when they were aligned into yarns. The yarns were woven into 3D orthogonal preforms to reinforce

Vinylester resin to produce high performance fiber reinforced composite materials. The mechanical properties of the high performance fiber reinforced composite materials were examined to find out how the single fiber of different high performance fibers and their yarns provide the performance to the composite materials in terms of tensile properties and impact properties (Tup, Izod and Charpy). The high performance fibers (Spectra®, Vectran® and Zylon®) were used as the filling yarns in x-direction. The fiber glass was used as y-yarns and z-yarns. The mechanical properties of the composite materials were tested in both x- direction and y-direction to assess the composites’ properties in terms of four high performance fibers, namely Spectra®, Vectran® and Zylon® and E-glass.

The single fiber tensile testing and yarn tensile testing indicate that Zylon® single fiber has the highest tensile strength when compared to other three, Zylon® fibers have relatively high tenacity and modulus when compared with other three high performance fibers. The difference in tensile properties of the four fibers highly related to the difference in their morphology, which was explained in details in the literature review chapter and results of single fiber tensile testing sections.

The yarn tensile testing indicates that yarn tensile tenacity of the high performance fibers is not as high as the calculated tensile tenacity using the single filament tensile tenacity. However, from the testing results, the yarns with relatively high filament counts tend to have lower tensile tenacity corresponding to their theoretical tensile tenacity. Higher number of filaments leads to longer fiber length in the tested portion of the yarn that leads to the possibility of having weak links and flaws.

It is well established that the fiber is the major load carrier in fiber reinforced composite materials. Tensile property testing has proved that the specimens reinforced with Zylon® fibers have the highest normalized

165 tensile stress and tensile tenacity in x-direction but still lower than that of calculated composite tensile strength using the single filament tensile strength and yarn tensile strength. This could be attributed to fibers damaged during handling, weaving process, exposure to UV-Vis and more importantly poor bonding between the fiber and resin. In this research, as the 3D woven preforms have the maximum construction in x-direction, fibers close to or on the edges of the specimens can be damaged during the cutting and have the limited ability to provide the tensile strength to the specimens. The high performance polymer fibers in this research have relatively poor transvers compressive strength which mentioned in the literature review, for this reason, these polymer fibers were easily damaged during the composite tensile testing as a result of high clamp pressure. The damaged x-fibers that close to the 3D orthogonal woven composite surface (both sides are x-fibers) also believed to be another reason that composite tensile specimens in x-direction were broken close or under the jaws which caused by the stress concentration around the jaw edge, as the clamping part will be compressed and have smaller thickness than the gauge length part. For specimens in y-direction, when considering the fiber in x-direction gives no contribution to the tensile strength in y- direction, the tensile stress in y-direction for all specimens was almost the same since the fibers in y- direction and z-direction for all composites were glass fibers of the same count and linear density.

The impact testing includes Dynatup, Izod and Charpy impact testing. From the impact testing results, composites specimens with Zylon® fibers in x-direction have relatively better Tup impact resistance and

Izod impact resistance. However, composites specimens with Vectran® fibers have the best performance in the Charpy impact testing and the disadvantage of their performance in Izod impact test is not significant when compared to the specimens with Zylon® fibers. As the composite specimens have better Charpy impact resistance in y-direction and better Izod impact resistance in x-direction except specimens with

Spectra® fibers, two reasons might contribute to this situation: 1) specimens were fixed by the clamp during

Izod impact tests while specimens were not clamped in Charpy tests; 2) specimen length in Charpy impact tests is much longer than that of specimens in Izod impact tests and polymer fibers are flexible.

166

From all the testing, composite with each high performance fiber has its own advantages and disadvantages such as the creep behavior of Spectra® fiber at low speed of loading will stop the composite break catastrophically but limited usage in high temperature applications as Spectra® fibers have relatively low decomposition temperature when compared with the other two high performance fibers as the x-yarns.

Zylon® fiber reinforced 3D orthogonal woven composites have better tensile strength and impact resistance in Izod impact tests and composites with Vectran® fibers have the relatively better impact resistance in both x- and y-direction in Charpy impact tests.

In this research as received high performance fibers were used without any treatment. It is suggested that research be conducted to modify the fiber surface to improve bonding between fibers and resin matrix.

Improvement in wettability of fibers is another feature that needs to be considered to allow the resin flow within and between tows. Optimization between bonding, wetting and fiber volume fraction is an important route to improve the composites tenacity to utilize the full strength of the fibers.

167

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173

APPENDICES

174

APPENDIX A: Yarn linear density determination testing

Fiber Spectra Vectran Zylon Fiber Glass Yarn linear density by manufacturer 1300 1500 1476 2475 6615 21600 (denier) Wraps 60 60 60 60 60 60 Specimen Length 54.864 54.864 54.864 54.864 54.864 54.864 (m) 8.029 9.533 8.910 14.760 42.990 130.098

Measured 8.064 9.553 8.912 14.750 43.020 131.250 Weight 8.087 9.535 8.911 14.690 42.990 131.080 (g) 8.025 9.562 8.920 14.790 43.080 131.110 8.070 9.563 8.914 14.770 43.040 131.070 Mean Weight 8.055 9.549 8.913 14.752 43.024 131.098 (g) Std. Dev. 0.027 0.014 0.004 0.038 0.038 0.098 CV, % 0.33% 0.15% 0.04% 0.26% 0.09% 0.07% Measured linear density 1321.36 1566.47 1462.17 2419.95 7057.74 21505.58 (denier)

175

APPENDIX B: Measured thickness of 3D orthogonal woven preform.

Fiber Spectra Vectran Zylon 3.26 3.38 3.12 3.24 3.44 3.20 Preform Thickness 3.12 3.40 3.26 Measurement (mm) 3.16 3.36 3.16 3.22 3.48 3.24 Average Measured Preform Thickness 3.20 3.41 3.20 (mm) Theoretical Preform 2.73 2.61 2.56 Thickness (mm)

176

APPENDIX C: Composite areal density measurements.

Average Areal Specimen Weight Area areal Fiber density No. (g) (m2) density (g/m2) (g/m2) 1 13.590 0.003613 3761 2 14.820 0.003775 3926 3 13.620 0.003775 3608 4 12.670 0.003482 3639 5 13.010 0.003487 3731 Spectra 1 16.960 0.004617 3673 3809 2 16.390 0.004495 3646 3 18.920 0.004477 4226 4 18.330 0.004437 4132 5 17.010 0.004437 3834 6 16.600 0.004456 3725 1 19.340 0.004642 4167 2 19.130 0.004493 4257 3 19.870 0.004485 4430 4 19.710 0.00448 4399 1 19.470 0.004479 4347 Vectran 4398 2 18.980 0.004415 4299 3 20.630 0.004401 4688 4 21.390 0.004627 4622 5 19.810 0.00452 4383 6 19.660 0.004481 4387 1 18.480 0.004581 4034 2 19.520 0.004605 4239 3 17.790 0.004595 3872 4 18.040 0.004692 3845 1 17.710 0.004602 3849 Zylon 3982 2 17.830 0.004399 4053 3 19.600 0.004588 4272 4 18.130 0.004504 4026 5 16.550 0.004322 3829 6 16.930 0.004453 3802

177

APPENDIX D: Fiber surface area

Vectran®

Spectra®

Zylon® Fiber

Filaments

No. of

996 300 240

0.164659 0.555556 0.601852

Fiber

g/km

Tex

Density

g/cm

Fiber Fiber

1.56 0.97

1.4

Diameter

0.001160 0.002250 0.002813

Fiber Fiber

picks/layer/cm

Density

11.648 11.004

9.926

Yarn

Number

layers

of of

4 4 4

Filaments/m

Numberof

4640649 1320521

952935

Total Total

Fiber Surface Fiber

Area

169

93 84

fabrics

178

APPENDIX E: Single fiber tensile testing results tables

Table E.1 All specimens for Spectra® single fiber tensile testing

Elong %Strn Peak Fiber Fiber Break Spcmn Denier @ @ Load Modulus Tenacity Energy Break Break No. Denier gf mm % gf/denier gf/denier J/denier 1 5.42 166.05 4.45 17.51 918.32 30.64 4.591 2 5.42 191.39 3.16 12.42 831.68 35.31 3.230 3 5.42 172.45 5.19 20.42 847.63 31.82 5.291 4 5.42 171.40 5.33 20.99 772.58 31.62 5.489 5 5.42 167.17 3.06 12.05 838.25 30.84 2.950 6 5.42 169.93 2.11 8.32 870.88 31.35 1.845 7 5.42 203.82 3.96 15.60 1121.07 37.61 4.896 8 5.42 168.76 4.74 18.64 937.56 31.14 4.975 9 5.42 163.29 3.63 14.29 868.83 30.13 3.565 10 5.42 169.26 4.45 17.54 916.69 31.23 4.620 11 5.42 167.69 2.70 10.62 699.74 30.94 2.351 12 5.42 173.86 2.11 8.32 884.78 32.08 1.893 13 5.42 169.03 3.04 11.97 1009.58 31.19 2.982 14 5.42 170.64 2.01 7.91 1048.52 31.48 1.791 15 5.42 174.73 2.49 9.82 979.94 32.24 2.430 16 5.42 138.87 1.47 5.78 612.74 25.62 0.849 17 5.42 171.11 3.63 14.29 1053.60 31.57 3.789 18 5.42 154.22 2.82 11.09 530.35 28.45 2.274 19 5.42 196.16 4.35 17.13 1208.94 36.19 5.178 20 5.42 167.69 3.81 15.02 906.63 30.94 3.782 Mean 171.38 3.43 13.49 892.92 31.62 3.438 Std. Dev. 13.76 1.11 4.36 161.93 2.54 1.386 CV, % 8% 32% 32% 18% 8% 40%

179

Table E.2 All specimens for Vectran single fiber tensile testing

Peak Elong @ %Strn @ Fiber Initial Fiber Spcmn Denier Break Load Break Break Modulus modulus Tenacity Energy No. Denier gf mm % gf/denier gf/denier gf/denier J/denier 1 5.00 146.44 1.28 5.06 883.37 576.01 29.29 0.719 2 5.00 139.82 1.26 4.97 671.76 516.15 27.96 0.686 3 5.00 143.45 1.23 4.86 663.89 540.41 28.69 0.715 4 5.00 172.21 1.48 5.82 1136.03 553.99 34.44 0.979 5 5.00 154.21 1.33 5.22 939.49 600.51 30.84 0.804 6 5.00 155.06 1.24 4.87 724.09 559.9 31.01 0.757 7 5.00 144.19 1.31 5.17 1152.4 484.32 28.84 0.756 8 5.00 176.89 1.23 4.84 828.5 713.37 35.38 0.826 9 5.00 145.12 1.24 4.87 972.55 555.41 29.02 0.722 10 5.00 132.97 1.03 4.04 724.53 605.72 26.59 0.576 11 5.00 157.19 1.41 5.54 844.12 546.36 31.44 0.898 12 5.00 159.69 1.26 4.97 743.76 586.27 31.94 0.791 13 5.00 95.28 0.9 3.54 655.72 496.07 19.06 0.311 14 5.00 149.17 1.23 4.86 651.46 600.19 29.83 0.717 15 5.00 166.56 1.2 4.71 795.21 557.72 33.31 0.747 16 5.00 193.36 1.33 5.25 848 765.25 38.67 1.033 17 5.00 150.5 1.22 4.8 738.73 530.82 30.1 0.678 18 5.00 142.86 1.32 5.19 661.95 550.33 28.57 0.774 19 5.00 144.27 1.31 5.14 995.95 589.77 28.85 0.761 20 5.00 185.11 1.2 4.71 919.47 726.73 37.02 0.849 Mean 152.72 1.25 4.92 827.55 582.77 30.54 0.755 Std. Dev. 20.81301 0.121978 0.481317 154.0924 73.834 4.162148 0.147 CV, % 14% 10% 10% 19% 13% 14% 20%

180

Table E.3 All specimens for Zylon single fiber tensile testing

Elong @ %Strn @ Fiber Fiber Spcmn Denier Peak Load Break Break Break Modulus Tenacity Energy No. Denier gf mm % gf/denier gf/denier J/denier 1 1.48 56.57 0.7 2.77 1819.46 38.22 0.577 2 1.48 49.81 0.69 2.71 1304.65 33.65 0.473 3 1.48 41.6 0.52 2.05 1403.49 28.11 0.290 4 1.48 50.96 0.56 2.19 2353.07 34.43 0.391 5 1.48 54.62 0.74 2.93 1333.34 36.9 0.571 6 1.48 50.52 0.76 2.99 1276.88 34.13 0.547 7 1.48 50.29 0.58 2.26 1865.17 33.98 0.404 Zylon 8 1.48 47.42 0.57 2.24 1672.68 32.04 0.373 Group 1 9 1.48 65.12 0.74 2.91 1490.6 44 0.670 10 1.48 53.85 0.74 2.9 1433.51 36.39 0.595 11 1.48 51.75 0.68 2.69 1325.65 34.97 0.475 12 1.48 45.91 0.57 2.26 1441.24 31.02 0.360 13 1.48 57.38 0.71 2.78 1903.53 38.77 0.586 14 1.48 53.84 0.68 2.66 1491.74 36.38 0.505 15 1.48 51.5 0.61 2.41 1631.01 34.8 0.428 16 1.48 51.41 0.64 2.53 2440.32 34.74 0.474 17 1.48 45.69 0.65 2.55 1408.38 30.87 0.410 18 1.48 56.54 0.74 2.9 1544.75 38.2 0.583 19 1.48 56.49 0.75 2.95 1635.13 38.17 0.594 20 1.48 51.75 0.69 2.7 1465.27 34.97 0.489 1 1.48 40.89 0.54 2.13 1546.21 27.63 0.301 2 1.48 54.35 0.7 2.75 1405.23 36.73 0.524 3 1.48 51.51 0.62 2.45 1668.34 34.8 0.446 4 1.48 60.54 0.75 2.94 2022.73 40.9 0.644 5 1.48 58.03 0.71 2.8 1765.09 39.21 0.585 6 1.48 36.51 0.58 2.3 1696.44 24.67 0.295 7 1.48 58.99 0.7 2.74 1939.6 39.86 0.576 8 1.48 54.87 0.77 3.03 1791.72 37.07 0.596 9 1.48 62.29 0.75 2.95 1567.6 42.09 0.663 Zylon 10 1.48 51.57 0.67 2.64 1690.59 34.85 0.487 Group 2 11 1.48 59.51 0.71 2.81 1905.63 40.21 0.607 13 1.48 52.5 0.55 2.17 1776.08 35.47 0.400 14 1.48 46.64 0.56 2.2 1647.82 31.52 0.362 16 1.48 53.45 0.7 2.76 1774.08 36.12 0.542 17 1.48 52.89 0.63 2.48 1706.85 35.74 0.465 18 1.48 51.97 0.62 2.43 1517.86 35.12 0.458 19 1.48 45.32 0.54 2.14 1661.41 30.62 0.341 20 1.48 52.44 0.71 2.78 1522.68 35.44 0.522 Mean 52.30 0.66 2.60 1653.84 35.34 0.490 Std. Dev. 5.848 0.0749 0.293 259.91 3.951 0.115 CV, % 11% 11% 11% 16% 11% 23%

181

Table E.4 All specimens for Fiber Glass 275 tex single fiber tensile testing

Elong %Strn Peak Fiber Fiber Break Spcmn Denier @ @ Load Modulus Tenacity Energy Break Break No. Denier gf mm % gf/denier gf/denier J/denier 1 6.548 32.66 0.76 3.01 192.22 4.99 0.078 3 6.548 34.95 1.06 4.19 142.01 5.34 0.117 4 6.548 50.41 0.86 3.38 309.62 7.70 0.136 5 6.548 50.16 0.91 3.58 257.20 7.66 0.145 6 6.548 51.65 0.78 3.07 359.60 7.89 0.128 Fiber 7 6.548 28.60 0.62 2.44 188.61 4.37 0.056 Glass 8 6.548 31.45 0.49 1.91 415.28 4.80 0.074 275 tex 9 6.548 27.24 0.93 3.67 447.01 4.16 0.084 10 6.548 51.10 0.84 3.30 359.10 7.80 0.135 11 6.548 26.01 0.62 2.43 240.23 3.97 0.050 12 6.548 28.16 0.71 2.79 161.15 4.30 0.062 13 6.548 45.45 0.65 2.55 278.73 6.94 0.123 14 6.548 50.13 0.56 2.19 412.71 7.66 0.091 15 6.548 34.77 0.57 2.24 289.81 5.31 0.094 16 6.548 28.86 0.74 2.90 185.35 4.41 0.067 17 6.548 19.80 0.64 2.51 134.40 3.02 0.039 18 6.548 27.41 0.93 3.68 159.33 4.19 0.081 19 6.548 18.99 0.61 2.39 226.97 2.90 0.037 20 6.548 31.23 0.92 3.62 131.92 4.77 0.092 Mean 35.21 0.75 2.94 257.43 5.38 0.089 Std. Dev. 11.02 0.16 0.63 102.33 1.68 0.034 CV, % 31% 21% 21% 40% 31% 38%

182

Table E.5 All specimens for Fiber Glass 735 tex single fiber tensile testing

Peak Elong @ %Strn Fiber Fiber Spcmn Denier Break Load Break @ Break Modulus Tenacity Energy No. Denier gf mm % gf/denier gf/denier J/denier 2 3.375 38.36 0.82 3.22 511 11.37 0.192 3 3.375 20.07 0.5 1.98 308.94 5.95 0.060 4 3.375 16.26 0.52 2.03 263.68 4.82 0.050 5 3.375 20.81 0.51 1.99 334.22 6.17 0.063 6 3.375 31.5 0.98 3.85 270.35 9.33 0.188 Fiber 7 3.375 42.94 0.86 3.37 409.41 12.72 0.223 Glass 8 3.375 35.12 1.02 4.03 289.75 10.4 0.220 735 tex 9 3.375 29.33 0.8 3.17 307.51 8.69 0.143 10 3.375 46.71 0.86 3.4 443.03 13.84 0.244 11 3.375 24.43 0.65 2.56 314.55 7.24 0.096 12 3.375 16.91 0.31 1.21 435.9 5.01 0.031 13 3.375 41.88 1.06 4.18 329.21 12.41 0.270 14 3.375 33.02 1.15 4.53 239.06 9.78 0.233 15 3.375 46.31 0.88 3.46 438.74 13.72 0.247 16 3.375 55.46 0.98 3.87 476.95 16.43 0.331 17 3.375 33.31 1 3.96 277.19 9.87 0.204 18 3.375 36.94 1.11 4.38 283.64 10.95 0.253 19 3.375 24.5 0.82 3.23 235.47 7.26 0.122 20 3.375 39.35 0.97 3.81 336.55 11.66 0.232 Mean 33.33 0.832 3.275 342.3763 9.88 0.179 Std. Dev. 10.931 0.233 0.924 83.848 3.238 0.086 CV, % 33% 28% 28% 24% 33% 48%

183

Table E.6 All specimens for Fiber Glass 2400 tex single fiber tensile testing

Peak Elong @ %Strn @ Fiber Fiber Spcmn Denier Break Load Break Break Modulus Tenacity Energy No. Denier gf mm % gf/denier gf/denier J/denier 1 5.51 53.62 0.73 2.87 380.86 9.73 0.146 2 5.51 33.1 0.35 1.38 448.38 6.01 0.042 3 5.51 42.08 0.8 3.15 261.77 7.64 0.125 4 5.51 48.8 0.64 2.52 377.96 8.86 0.115 5 5.51 36.16 0.73 2.88 238.5 6.56 0.097 Fiber 6 5.51 60.95 0.82 3.23 370.17 11.06 0.185 Glass 7 5.51 49.77 0.82 3.22 301.15 9.03 0.151 2400 tex 8 5.51 36.54 0.86 3.39 210.96 6.63 0.117 9 5.51 42.33 0.77 3.02 274.37 7.68 0.120 10 5.51 93.44 1.02 4.02 477.36 16.96 0.361 11 5.51 82.43 0.87 3.43 479.74 14.96 0.267 12 5.51 59.14 0.67 2.65 431.47 10.73 0.147 13 5.51 72.98 0.95 3.75 390.93 13.24 0.259 14 5.51 44.42 0.67 2.66 318.5 8.06 0.110 15 5.51 40.45 0.82 3.22 247.55 7.34 0.123 16 5.51 54.62 0.87 3.42 314.49 9.91 0.175 17 5.51 62.24 1.01 3.97 314.96 11.3 0.233 18 5.51 45.43 0.71 2.81 314.54 8.25 0.119 19 5.51 41.93 1.03 4.06 208.07 7.61 0.161 20 5.51 72.79 1.16 4.56 333.96 13.21 0.316 Mean 53.661 0.815 3.2105 334.7845 9.7385 0.168 Std. Dev. 16.38 0.176 0.691 83.30 2.972 0.080 CV, % 31% 22% 22% 25% 31% 47%

184

APPENDIX F: Yarn tensile testing result tables

Table F.1 All specimens for Spectra® yarn tensile testing

Break Break Peak Break Strai Modulus Tenacity Energy Specimen load Elongation Denier n (J/denier No. (gf/denier) (gf/denier) ) (gf) (mm) (%)

1 1300 37820.8 14.3 5.64 1016.15 29.09 1.048

2 1300 42106 14.3 5.64 1067.58 32.39 1.138

3 1300 45509.4 21.4 8.44 1093.13 35.01 2.028

Spectra 4 1300 41771.4 12.3 4.84 1122.06 32.13 0.943

s1000 5 1300 44430.3 15.8 6.24 1176.24 34.18 1.386

6 1300 42378 14.8 6.04 1083.11 32.60 1.204

7 1300 40507.9 13.3 5.24 1083.15 31.16 1.008

8 1300 44553.9 16.4 6.44 1124.9 34.27 1.389

9 1300 39044.4 13.3 5.24 1081.7 30.03 0.986

10 1300 43445.6 13.8 5.44 1120 33.42 1.106

Mean 42156.7 14.97 5.92 1096.80 32.43 1.223

Std. Dev. 2477.07 2.56 1.01 42.49 1.91 0.322

CV(%) 6% 17% 17% 4% 6% 26%

185

Table F.2 All specimens for Vectran yarn tensile testing

Peak Break Break Fiber Fiber Break Specimen Denier load Elongation Strain Modulus Tenacity Energy No. (gf) (mm) (%) (gf/denier) (gf/denier) (J/denier)

1 1500 43000.1 11.3 4.44 787.40 28.67 0.607

2 1500 39285.2 10.3 4.24 776.41 26.19 0.524

3 1500 44058.8 10.8 4.24 836.27 29.37 0.563

4 1500 43603.4 11.3 4.44 744.03 29.07 0.604 Vectran

HT 5 1500 43489.5 10.8 4.24 798.88 28.99 0.573

6 1500 41977 11.3 4.44 807.58 27.98 0.580

7 1500 41945.9 10.8 4.24 844.09 27.96 0.543

8 1500 44330.8 11.3 4.44 843.55 29.55 0.607

9 1500 44346.4 11.8 4.64 785.18 29.56 0.658

10 1500 43598.2 10.8 4.24 887.30 29.07 0.567 Mean 42963.53 11.05 4.36 811.07 28.64 0.582

Std. Dev. 1549.57 0.42 0.14 41.74 1.03 0.038

CV(%) 4% 4% 3% 5% 4% 7%

186

Table F.3 All specimens for Zylon yarn tensile testing

Break Peak Break Break Fiber Fiber Energy Specimen Denier load Elongation Strain Modulus Tenacity (J/denier (gf) (mm) (%) (gf/denier) (gf/denier) )

1 1476 45645.8 6.7 2.64 1357.96 30.93 0.423

2 1476 45732.3 7.2 2.84 1352.17 30.98 0.471

3 1476 42799.8 6.7 2.84 1373.8 29.00 0.468

Zylon 4 1476 45318.8 7.2 2.84 1359.15 30.70 0.475

HM 5 1476 45315.7 6.7 2.64 1342.24 30.70 0.417

6 1476 50120.6 8.2 3.24 1359.53 33.96 0.618

7 1476 46349.4 7.2 2.84 1351.64 31.40 0.479

8 1476 48847.4 7.7 3.04 1343.7 33.09 0.540

9 1476 46829 6.7 2.64 1357.74 31.73 0.429

10 1476 46116.7 7.2 2.84 1296.28 31.24 0.468

Mean 46307.55 7.15 2.84 1349.42 31.37 0.479

Std. Dev. 2009.28 0.50 0.19 20.69 1.36 0.060

CV(%) 4% 7% 7% 2% 4% 13%

187

Table F.4 All specimens for Fiber Glass 275 tex yarn tensile testing

Break Break Peak Break Fiber Fiber Elongatio Energy load Strain Modulus Tenacity Specimen Denier n (J/denier)

(gf) (%) (gf/denier) (gf/denier) (mm)

1 2475 14238.6 5.2 2.44 310.66 5.75 0.0793

2 2475 15724.6 5.7 2.44 311.65 6.35 0.0830

3 2475 17866.3 6.2 2.44 320.8 7.22 0.0876 Fiber 4 2475 17204.8 6.2 2.44 337.88 6.95 0.0896 Glass 5 2475 17471.4 6.2 2.44 322.75 7.06 0.0862 275 tex 6 2475 18753.8 6.7 2.64 324.69 7.58 0.0994

7 2475 16795.6 5.7 2.43 336.45 6.79 0.0888

8 2475 19128.6 6.7 2.63 322.86 7.73 0.0982

9 2475 18739 6.7 2.84 310 7.57 0.1039

10 2475 18571.1 6.7 2.64 326.72 7.5 0.1039 Mean 17449.38 6.2 2.54 322.45 7.05 0.0920

Std. Dev. 1541.58 0.53 0.14 9.84 0.62 0.0087

CV(%) 9% 9% 6% 3% 9% 9%

188

Table F.5 All specimens for Fiber Glass 735 tex yarn tensile testing

Peak Break Break Fiber Fiber Break Energy Specimen Denier load Elongation Strain Modulus Tenacity (J/denier) (gf) (mm) (%) (gf/denier) (gf/denier)

1 6615 44663.3 6.2 2.84 322.37 6.75 0.1034

2 6615 48940.9 7.2 2.84 301.77 7.4 0.1033

3 6615 44363.3 6.7 2.64 306.54 6.71 0.0904

Fiber 4 6615 48580.9 6.7 2.84 310.94 7.34 0.1051

Glass 5 6615 49717.1 6.7 2.84 325.21 7.52 0.1034

735 6 6615 43525.9 6.2 2.84 314.46 6.58 0.1003 tex 7 6615 43308.8 6.2 2.63 328.34 6.55 0.0921

8 6615 49433.2 6.7 2.84 330.47 7.47 0.1043

9 6615 48721.7 6.7 2.64 321.29 7.37 0.0950

10 6615 42759.1 6.2 2.84 308.33 6.46 0.0952

Mean 46401.42 6.55 2.78 316.97 7.02 0.0993

Std. Dev. 2887.57 0.34 0.10 9.91 0.44 0.0056

CV(%) 6% 5% 4% 3% 6% 6%

189

Table F.6 All specimens for Fiber Glass 2400 tex yarn tensile testing

Break Break Fiber Fiber Break Peak load Energy Specimen Denier Elongation Strain Modulus Tenacity (J/denier) (gf) (mm) (%) (gf/denier) (gf/denier)

1 21600 120846.3 6.7 3.04 259.45 5.59 0.0857

2 21600 127199.2 6.7 3.04 257.8 5.89 0.0932

3 21600 111627.2 6.2 3.04 262.39 5.17 0.0874

Fiber 4 21600 108256.4 6.2 2.84 256.42 5.01 0.0782

Glass 5 21600 114239.5 6.7 3.04 257.85 5.29 0.0860

2400 6 21600 111908 5.7 2.64 267.76 5.18 0.0744 tex 7 21600 128005.9 7.2 3.04 261.24 5.93 0.0966

8 21600 116640.9 6.2 2.84 259.42 5.4 0.0858

9 21600 120844.2 6.7 2.84 258.55 5.59 0.0832

10 21600 119421.2 6.7 2.84 254.65 5.53 0.0840

Mean 117898.88 6.5 2.92 259.55 5.46 0.0855

Std. Dev. 6257.02 0.4 0.14 3.45 0.29 0.0064

CV(%) 5% 6% 5% 1% 5% 8%

190

APPENDIX G Orthogonal woven preforms reinforced composite tensile testing results

Table G.1 Specimens for Spectra Panel 2, extensometer used.

Peak Peak Tenacity Break Specimen Direction Thickness Width Strain Load Stress Energy ID (mm) (mm) (N) (Mpa) (%) gf/denier J/denier 1 x 2.84 28.12 30126.18 377.06 3.15 21.16 0.938 2 x 2.76 27.87 35161.91 456.62 3.94 24.92 1.268 3 x 2.65 28.21 34860.27 466.72 3.13 24.42 1.155 4 x 2.58 27.57 33611.99 472.96 3.65 24.09 1.176 5 x 2.52 26.87 34874.34 514.42 4.06 25.64 1.351 6 x 2.33 27.76 29844.47 461.76 3.51 21.24 1.028 Spectra Average 2.61 27.73 33079.86 458.26 3.57 23.6 1.153 Panel 2 Std. Dev. 0.18 0.48 2457.64 44.83 0.39 1.92 0.152 CV. % 7% 2% 7% 10% 11% 8% 13%

1 y 2.95 28.36 30609.20 366.15 4.31 7.71 0.216 2 y 2.82 28.24 35125.22 440.80 2.61 8.89 0.263 3 y 2.79 28.33 32694.80 413.54 2.84 8.25 0.227 4 y 2.87 27.34 30064.46 383.33 2.44 7.86 0.192 6 y 2.48 28.28 28558.11 407.36 2.38 7.22 0.191 Average 2.78 28.11 31410.36 402.24 2.92 7.99 0.218 Std. Dev. 0.18 0.47 2900.36 23.62 0.21 0.626027 0.034 CV. % 6% 2% 9% 6% 7% 8% 16%

191

Table G.2 Specimens for Vectran Panel 2, extensometer used.

Peak Peak Tenacity Break Specimen Direction Thickness Width Strain Load Stress Energy ID (mm) (mm) (N) (Mpa) (%) (gf/denier) (J/denier) 1 x 3.00 27.31 38405.83 469.13 2.39 21.72 0.651 2 x 3.02 28.30 35537.43 415.71 2.29 19.40 0.565 3 x 2.91 28.37 40262.25 487.28 2.67 21.92 0.753 4 x 2.85 27.65 40334.83 511.79 2.74 22.53 0.747 5 x 2.80 27.86 38935.92 499.43 2.47 21.58 0.709 6 x 2.87 28.73 38826.30 470.71 2.25 20.87 0.684 Vectran Average 2.91 28.04 38717.09 475.68 2.47 21.34 0.685 Panel 2 Std. Dev. 0.09 0.52 1747.66 33.66 0.20 1.091 0.070 CV. % 3% 2% 5% 7% 8% 5% 10%

Peak Peak Tenacity Break Specimen Direction Thickness Width Strain Load Stress Energy ID (mm) (mm) (N) (Mpa) (%) (gf/denier) (J/denier) 1 y 3.06 27.11 32904.87 396.65 2.72 8.67 0.227 2 y 3.00 27.56 31842.40 385.09 2.97 8.26 0.216 3 y 3.04 27.53 31755.63 378.94 3.97 8.24 0.219 4 y 2.90 27.33 32432.43 408.60 3.18 8.48 0.218 5 y 2.85 27.86 32297.09 407.52 1.94 8.29 0.221 6 y 2.72 27.56 32293.29 430.84 0.83 8.38 0.220 Average 2.93 27.49 32254.29 401.27 2.60 8.39 0.220 Std. Dev. 0.13 0.25 418.73 18.70 1.09 0.166875 0.004 CV. % 4% 1% 1% 5% 42% 2% 2%

192

Table G.3 Specimens for Zylon Panel 2, extensometer used.

Peak Peak Tenacity Break Specimen Direction Thickness Width Strain Load Stress Energy ID (mm) (mm) (N) (Mpa) (%) (gf/denier) (J/denier) 1 x 2.57 27.96 54544.11 758.47 2.27 28.93 1.091 2 x 2.53 27.41 49294.14 711.11 1.74 26.67 1.443 3 x 2.40 27.99 51370.52 763.52 1.86 27.22 0.794 4 x 2.29 27.53 52317.84 831.23 1.91 28.17 0.900 5 x 2.20 26.73 50150.03 853.10 1.58 27.82 0.803 6 x 2.25 28.24 51999.58 820.20 1.57 27.30 0.640 Average 2.37 27.64 51612.70 789.61 1.82 27.68 0.945 Zylon Std. Dev. 0.15 0.54 1833.78 53.87 0.26 0.800 0.285 Panel CV. % 7% 2% 4% 7% 14% 30% 2 3%

Peak Peak Tenacity Energy Specimen Direction Thickness Width Strain Load Stress ID (mm) (mm) (N) (Mpa) (%) (gf/denier) (J/denier) 1 y 2.65 26.66 31660.78 449.07 3.01 8.49 0.221 2 y 2.65 28.04 30702.16 412.61 3.79 7.83 0.204 3 y 2.60 27.97 32518.30 447.21 2.71 8.31 0.226 4 y 2.50 27.34 29562.58 432.39 3.04 7.73 0.189 5 y 2.30 26.65 26598.16 434.69 1.63 7.13 0.177 6 y 2.28 25.66 25505.03 435.18 0.72 7.10 0.169 Average 2.50 27.05 29424.50 435.19 2.48 7.77 0.198 Std. Dev. 0.17 0.91 2813.34 13.08 1.11 0.577 0.023 CV. % 7% 3% 10% 3% 45% 7% 12%

193

APPENDIX H Tup impact testing results tables

Table H.1 Normalized peak force for Spectra®

Normalized Peak Force Peak Total Specimen Thickness Force Displacement Preform Composite Thickness areal areal density density No. mm N mm N/mm N/(g/m2) N/(g/m2) 1 2.490 6843.74 23.451 2748.49 2.678 1.820 2 2.680 6079.63 22.999 2268.52 2.379 1.549 3 2.300 5771.17 19.521 2509.20 2.258 1.600 4 2.390 6517.36 22.476 2726.93 2.550 1.791 Spectra 5 2.310 6502.00 23.137 2814.72 2.544 1.743 1 2.791 8246.54 21.548 2954.69 3.226 2.245 2 2.798 8188.94 19.334 2926.71 3.204 2.246 3 3.113 8275.98 17.681 2658.52 3.238 1.959 4 3.015 7862.56 20.485 2607.81 3.076 1.903 5 2.834 8039.19 19.339 2836.69 3.145 2.097 6 2.838 7884.32 18.555 2778.13 3.085 2.116 Mean 2.687 7291.948 20.775 2711.86 2.853 1.915 Std. Dev. 0.278 955.321 2.037 197.115 0.374 0.241 CV,% 10% 13% 10% 7% 13% 13%

194

Table H.2 Normalized energy for Spectra®

Normalized Energy Total Specimen Thickness Energy Displacement Preform Composite Thickness areal areal density density No. mm J mm J/mm J/(g/m2) J/(g/m2) 1 2.490 47.26 23.451 18.98 0.0185 0.0126 2 2.680 45.63 22.999 17.03 0.0179 0.0116 3 2.300 39.48 19.521 17.17 0.0154 0.0109 Spectra 4 2.390 49.85 22.476 20.86 0.0195 0.0137 5 2.310 54.13 23.137 23.43 0.0212 0.0145 1 2.791 50.13 21.548 17.96 0.0196 0.0136 2 2.798 46.10 19.334 16.48 0.0180 0.0126 3 3.113 50.95 17.681 16.37 0.0199 0.0121 4 3.015 49.23 20.485 16.33 0.0193 0.0119 5 2.834 49.65 19.339 17.52 0.0194 0.0130 6 2.838 48.79 18.555 17.19 0.0191 0.0131 Mean 2.687 48.292 20.775 18.12 0.0189 0.0127 Std. Dev. 0.278 3.747 2.037 2.209 0.001 0.001 CV,% 10% 8% 10% 12% 8% 8%

195

Table H.3 Normalized peak force for Vectran®

Normalized Peak Force Peak Total Specimen Thickness Force Displacement Preform Composite Thickness areal areal density density No. mm N mm N/mm N/(g/m2) N/(g/m2) 1 2.630 6770.79 24.479 2574.44 2.449 1.625 2 2.710 6472.57 24.256 2388.40 2.341 1.520 3 2.970 6967.89 22.583 2346.09 2.520 1.573 Vectran 4 2.840 6638.96 21.181 2337.66 2.401 1.509 1 2.791 8246.54 21.548 2954.69 2.982 1.897 2 2.798 8188.94 19.334 2926.71 2.962 1.905 3 3.113 8275.98 17.681 2658.52 2.993 1.766 4 3.015 7862.56 20.485 2607.81 2.844 1.701 5 2.834 8039.19 19.339 2836.69 2.907 1.834 6 2.838 7884.32 18.555 2778.13 2.851 1.797 Mean 2.854 7534.77 20.944 2640.92 2.725 1.713 Std. Dev. 0.143 730.585 2.317 232.322 0.264 0.150 CV,% 5% 10% 11% 9% 10% 9%

196

Table H.4 Normalized energy for Vectran®

Normalized Energy Total Specimen Thickness Energy Displacement Preform Composite Thickness areal areal density density No. mm J mm J/mm J/(g/m2) J/(g/m2) 1 2.630 44.616 24.479 16.96 0.0161 0.0107 2 2.710 43.925 24.256 16.21 0.0159 0.0103 3 2.970 46.830 22.583 15.77 0.0169 0.0106 Vectran 4 2.840 42.993 21.181 15.14 0.0155 0.0098 1 2.791 50.125 21.548 17.96 0.0181 0.0115 2 2.798 46.104 19.334 16.48 0.0167 0.0107 3 3.113 50.948 17.681 16.37 0.0184 0.0109 4 3.015 49.233 20.485 16.33 0.0178 0.0107 5 2.834 49.654 19.339 17.52 0.0180 0.0113 6 2.838 48.789 18.555 17.19 0.0176 0.0111 Mean 2.854 47.32 20.944 16.59 0.017 0.011 Std. Dev. 0.143 2.820 2.317 0.837 0.001 0.001 CV,% 5% 6% 11% 5% 6% 5%

197

Table H.5 Normalized peak force for Zylon®

Normalized Peak Force Peak Total Specimen Thickness Preform Composite Force Displacement Thickness areal areal density density No. mm N mm N/mm N/(g/m2) N/(g/m2) 1 2.490 8991.45 21.574 3611.02 3.224 2.229 2 2.320 9182.16 21.357 3957.83 3.292 2.166 3 2.230 8722.67 21.731 3911.51 3.128 2.253 4 2.420 9326.79 22.781 3854.05 3.344 2.426 Zylon 1 2.333 10293.13 19.752 4411.97 3.691 2.675 2 2.349 9669.81 19.504 4116.56 3.467 2.386 3 2.719 10410.88 20.981 3828.94 3.733 2.437 4 2.369 10037.15 21.029 4236.87 3.599 2.493 5 2.278 10382.73 22.222 4557.83 3.723 2.712 6 2.211 9900.20 21.383 4477.70 3.550 2.604 Mean 2.372 9691.70 21.231 4096.43 3.475 2.438 Std. Dev. 0.148 609.363 1.004 315.749 0.218 0.187 CV,% 6% 6% 5% 8% 6% 8%

198

Table H.6 Normalized energy for Zylon®

Normalized Energy Total Specimen Thickness Energy Preform Composite Displacement Thickness areal areal density density No. mm J mm J/mm J/(g/m2) J/(g/m2) 1 2.490 65.601 21.574 26.35 0.0235 0.0163 2 2.320 75.409 21.357 32.50 0.0270 0.0178 3 2.230 61.591 21.731 27.62 0.0221 0.0159 4 2.420 65.153 22.781 26.92 0.0234 0.0169 Zylon 1 2.333 71.015 19.752 30.44 0.0255 0.0185 2 2.349 73.528 19.504 31.30 0.0264 0.0181 3 2.719 70.525 20.981 25.94 0.0253 0.0165 4 2.369 75.1 21.029 31.70 0.0269 0.0187 5 2.278 74.367 22.222 32.65 0.0267 0.0194 6 2.211 68.558 21.383 31.01 0.0246 0.0180 Mean 2.372 70.08 21.231 29.64 0.025 0.018 Std. Dev. 0.148 4.757 1.004 2.641 0.002 0.001 CV,% 6% 7% 5% 9% 7% 7%

199

APPENDIX I Charpy impact testing results tables

Table I.1 Charpy impact specimens for Spectra® in X direction

Spectra Panel 2, x-direction Absolved Result Impact Specimen Thickness Width REL RE Energy Energy Speed Percent No. (mm) (mm) (J) (m/s) (J/m) (KJ/m2) (%) 1 2.746 13.34 7.12 3.554 2594 194 32.97 2 2.584 13.26 6.84 3.763 2649 200 31.67 3 2.538 12.80 5.02 3.554 1976 154 23.21 4 2.412 13.68 6.15 3.554 2552 187 28.49 5 2.613 13.73 6.47 3.554 2477 180 29.95 6 2.666 13.10 6.85 3.554 2569 196 31.70 Mean 2.593 13.32 6.41 3.589 2469 185 29.66 Std. Dev 0.114 0.352 0.76 0.085 248 17 3.526 CV, % 4% 3% 12% 2% 10% 9% 12%

200

Table I.2 Charpy impact specimens for Spectra® in Y direction

Spectra Panel 2, y-direction Absolved Result Impact Specimen Thickness Width REL RE Energy Energy Speed Percent No. (mm) (mm) (J) (m/s) (J/m) (KJ/m2) (%) 1 3.325 13.94 5.974 3.763 1797 129 27.65 2 3.014 13.85 7.743 3.763 2569 185 35.84 3 2.959 12.74 9.629 3.554 3254 255 44.57 4 2.757 14.05 8.081 3.554 2931 209 37.40 5 2.659 13.88 7.407 3.763 2786 201 34.28 6 2.393 13.47 6.655 3.763 2781 206 30.80 Mean 2.851 13.655 7.582 3.693 2686 198 35.09 Std. Dev 0.322 0.489 1.260 0.108 491 41 5.834 CV, % 11% 4% 17% 3% 18% 21% 17%

201

Table I.3 Charpy impact specimens for Vectran in X direction

Vectran Panel 2, x-direction Absolved Result Impact Specimen Thickness Width REL RE Energy Energy Speed Percent No. (mm) (mm) (J) (m/s) (J/m) (KJ/m2) (%) 1 2.942 13.54 10.962 3.554 3726 275 50.74 2 2.844 12.84 10.771 3.763 3787 295 49.85 3 2.829 13.10 9.044 3.763 3197 244 41.86 4 2.538 13.73 10.104 3.763 3981 290 46.77 5 2.790 13.37 10.054 3.763 3604 270 46.53 6 2.930 13.66 11.425 3.554 3899 285 52.88 Mean 2.812 13.37 10.393 3.693 3699 277 48.11 Std. Dev 0.147 0.345 0.843 0.108 279 18 3.900 CV, % 5% 3% 8% 3% 8% 7% 8%

202

Table I.4 Charpy impact specimens for Vectran in Y direction

Vectran Panel 2, y-direction Absolved Result Impact Specimen Thickness Width REL RE Energy Energy Speed Percent No. (mm) (mm) (J) (m/s) (J/m) (KJ/m2) (%) 1 2.985 14.08 12.962 3.554 4342 308 60.00 2 3.078 12.78 11.595 3.554 3767 295 53.67 3 3.081 14.81 8.241 3.554 2675 181 38.14 4 2.901 12.61 11.695 3.763 4032 320 54.13 5 2.935 14.25 13.176 3.554 4489 315 60.99 6 2.701 14.21 11.475 3.554 4248 299 53.11 Mean 2.947 13.79 11.524 3.589 3926 286 53.34 Std. Dev 0.141 0.886 1.767 0.085 663 53 8.18 CV, % 5% 6% 15% 2% 17% 18% 15%

203

Table I.5 Charpy impact specimens for Zylon in X direction

Zylon Panel 2, x-direction Absolved Result Impact Specimen Thickness Width REL RE Energy Energy Speed Percent No. (mm) (mm) (J) (m/s) (J/m) (KJ/m2) (%) 1 2.613 13.28 9.569 3.554 3662 276 44.29 2 2.442 13.65 6.868 3.554 2812 206 31.79 3 2.407 13.89 8.541 3.763 3548 255 39.53 4 2.277 13.21 5.917 3.763 2599 197 27.39 5 2.213 13.83 5.365 3.763 2424 175 24.83 Mean 2.390 13.57 7.252 3.679 3009 222 33.57 Std. Dev 0.156 0.312 1.769 0.114 563 42 8.19 CV, % 7% 2% 24% 3% 19% 19% 24%

204

Table I.6 Charpy impact specimens for Zylon in Y direction

Zylon Panel 2, y-direction Absolved Result Impact Specimen Thickness Width REL RE Energy Energy Speed Percent No. (mm) (mm) (J) (m/s) (J/m) (KJ/m2) (%) 1 2.862 13.19 7.652 3.554 2674 203 35.42 2 2.709 14.00 9.123 3.554 3368 241 42.22 3 2.434 14.08 11.273 3.763 4631 329 52.18 4 2.507 13.71 9.173 3.763 3659 267 42.46 5 2.516 13.19 10.709 3.554 4256 323 49.57 Mean 2.601 13.63 9.586 3.638 3717 272 43.37 Std. Dev 0.176 0.428 1.434 0.114 765 54 6.64 CV, % 7% 3% 15% 3% 21% 21% 15%

205

Table I.7 Tukey multiple comparison ANOVA table for Charpy impact resistance (REL) in x-direction.

type REL LSMEAN LSMEAN Number xSpectra 2469.21849 1 xVectran 3699.04408 2 xZylon 3009.15021 3

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: REL i/j 1 2 3 1 <.0001 0.0320 2 <.0001 0.0088 3 0.0320 0.0088

Table I.8 Tukey multiple comparison ANOVA table for Charpy impact strength (RE) in x-direction.

type RE LSMEAN LSMEAN Number xSpectra 185.256747 1 xVectran 276.521175 2 xZylon 221.853080 3

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: RE i/j 1 2 3 1 <.0001 0.0418 2 <.0001 0.0048 3 0.0418 0.0048

206

Table I.9 Tukey multiple comparison ANOVA table for Charpy impact resistance (REL) in y-direction.

type REL LSMEAN LSMEAN Number ySpectra 2686.26463 1 yVectran 3925.60911 2 yZylon 3717.50329 3

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: REL i/j 1 2 3 1 0.0048 0.0187 2 0.0048 0.6000 3 0.0187 0.6000

Table I.10 Tukey multiple comparison ANOVA table for Charpy impact strength (RE) in y-direction.

type RE LSMEAN LSMEAN Number ySpectra 197.595939 1 yVectran 286.251877 2 yZylon 272.345103 3

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: RE i/j 1 2 3 1 0.0075 0.0250 2 0.0075 0.6478 3 0.0250 0.6478

207

APPENDIX J Izod impact testing result tables

Table J.1 Izod impact specimens for Spectra® in X-direction

Absolved Specimen Thickness Width Result Impact REL RE Break Energy Energy Speed Percent No. (mm) (mm) (J/m) (KJ/m2) Type (J) (m/s) (%) 1 2.919 12.94 11.14 3.763 3818 295 50.64 NB 2 2.798 12.5 11.18 3.763 3996 320 50.80 NB 3 2.756 11.62 8.39 3.763 3045 262 38.14 NB 4 2.68 13.6 8.77 3.554 3272 241 39.86 NB 5 2.528 14.06 7.57 3.554 2996 213 34.42 NB 6 2.454 12.27 4.24 3.554 1729 141 19.28 NB Avg. 2.689 12.832 8.55 3.659 3143 245 38.85 Std. Dev. 0.173 0.895 2.58 0.114 804 64 11.71 CV, % 6% 7% 30% 3% 26% 26% 30%

Table J.2 Izod impact specimens for Spectra® in Y-direction

Absolved Specimen Thickness Width Result Impact REL RE Break Energy Energy Speed Percent No. (mm) (mm) (J/m) (KJ/m2) Type (J) (m/s) (%) 1 2.863 12.91 8.29 3.763 2896 224 37.68 H 2 2.794 12.83 11.95 3.763 4278 333 54.31 H 3 2.617 12.14 9.92 3.763 3791 312 45.08 H 4 2.691 13.77 7.60 3.763 2826 205 34.55 H 5 2.748 12.58 12.41 3.763 4515 359 56.39 H 6 2.527 13.13 6.02 3.763 2381 181 27.34 H Avg. 2.707 12.893 9.37 3.763 3448 269 42.56 Std. Dev. 0.122 0.547 2.52 0.000 869 75 11.45 CV, % 5% 4% 27% 0% 25% 28% 27%

208

Table J.3 Izod impact specimens for Vectran in X-direction

Absolved Specimen Thickness Width Result Impact REL RE Break Energy Energy Speed Percent No. (mm) (mm) (J/m) (KJ/m2) Type (J) (m/s) (%) 1 3.097 13.95 12.09 3.763 3905 280 54.96 NB 2 3.006 14.24 13.27 3.763 4415 310 60.31 NB 3 2.919 13.37 11.06 3.763 3790 283 50.27 NB 4 2.575 13.95 9.97 3.763 3872 278 45.31 NB 5 2.727 14.42 12.03 3.763 4413 306 54.68 NB 6 2.768 12.46 9.73 3.554 3517 282 44.24 NB Avg. 2.849 13.732 11.36 3.728 3985 290 51.63 Std. Dev. 0.194 0.718 1.36 0.085 359 14 6.20 CV, % 7% 5% 12% 2% 9% 5% 12%

Table J.4 Izod impact specimens for Vectran in Y-direction

Absolved Specimen Thickness Width Result Impact REL RE Break Energy Energy Speed Percent No. (mm) (mm) (J/m) (KJ/m2) Type (J) (m/s) (%) 1 3.124 13.47 12.66 3.554 4053 301 57.54 H 2 2.922 14.18 13.55 3.763 4637 327 61.57 H 3 2.87 12.36 7.75 3.554 2702 219 35.24 H 4 2.886 14.04 8.28 3.763 2869 204 37.63 H 5 2.828 14.73 11.03 3.554 3901 265 50.13 H 6 2.799 12.52 9.70 3.554 3467 277 44.10 H Avg. 2.905 13.55 10.50 3.624 3605 265 47.70 Std. Dev. 0.116 0.950 2.34 0.108 739 47 10.63 CV, % 4% 7% 22% 3% 20% 18% 22%

209

Table J.5 Izod impact specimens for Zylon in X-direction

Absolved Specimen Thickness Width Result Impact REL RE Break Energy Energy Speed Percent No. (mm) (mm) (J/m) (KJ/m2) Type (J) (m/s) (%) 1 2.605 12.56 10.11 3.763 3879 309 45.92 NB 2 2.619 13.41 11.21 3.763 4279 319 50.92 NB 3 2.526 12.74 12.40 3.554 4908 385 56.34 NB 4 2.317 13.58 7.09 3.763 3062 225 32.24 NB 5 2.426 13.81 9.39 3.554 3869 280 42.65 NB 6 2.314 13.33 9.91 3.763 4282 321 45.03 NB Avg. 2.468 13.24 10.02 3.693 4046 307 45.52 Std. Dev. 0.137 0.488 1.79 0.108 614 53 8.14 CV, % 6% 4% 18% 3% 15% 17% 18%

Table J.6 Izod impact specimens for Zylon in Y-direction

Absolved Specimen Thickness Width Result Impact REL RE Break Energy Energy Speed Percent No. (mm) (mm) (J/m) (KJ/m2) Type (J) (m/s) (%) 1 2.699 14.41 15.85 3.554 5874 408 72.04 H 2 2.385 14.84 8.58 3.554 3596 242 38.97 H 3 2.577 14.37 8.12 3.554 3150 219 36.89 H 4 2.44 12.45 8.17 3.763 3348 269 37.12 H 5 2.374 13.81 10.99 3.763 4629 335 49.94 H 6 2.229 14.00 6.93 3.763 3107 222 31.47 H Avg. 2.451 13.98 9.77 3.659 3951 283 44.41 Std. Dev. 0.166 0.830 3.26 0.114 1095 75 14.84 CV, % 7% 6% 33% 3% 28% 26% 33%

210

Table J.7 Tukey multiple comparison ANOVA table for Izod impact resistance (REL) in x-direction.

type REL LSMEAN LSMEAN Number xSpectra 3142.59027 1 xVectran 3985.24434 2 xZylon 4046.44626 3

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: REL i/j 1 2 3 1 0.0325 0.0232 2 0.0325 0.8664 3 0.0232 0.8664

Table J.8 Tukey multiple comparison ANOVA table for Izod impact strength (RE) in x-direction.

type RE LSMEAN LSMEAN Number xSpectra 245.222346 1 xVectran 289.876815 2 xZylon 306.669827 3

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: RE i/j 1 2 3 1 0.1308 0.0439 2 0.1308 0.5567 3 0.0439 0.5567

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Table J.9 Tukey multiple comparison ANOVA table for Izod impact resistance (REL) in y-direction.

type REL LSMEAN LSMEAN Number ySpectra 3447.65143 1 yVectran 3604.67914 2 yZylon 3950.62277 3

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: REL i/j 1 2 3 1 0.7699 0.3551 2 0.7699 0.5216 3 0.3551 0.5216

Table J.10 Tukey multiple comparison ANOVA table for Izod impact strength (RE) in y-direction.

type RE LSMEAN LSMEAN Number ySpectra 269.236958 1 yVectran 265.422804 2 yZylon 282.529466 3

Least Squares Means for effect type Pr > |t| for H0: LSMean(i)=LSMean(j) Dependent Variable: RE i/j 1 2 3 1 0.9225 0.7350 2 0.9225 0.6635 3 0.7350 0.6635

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