REINFORCEMENT of SYNTACTIC FOAM with Sic NANOPARTICLES
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REINFORCEMENT OF SYNTACTIC FOAM WITH SiC NANOPARTICLES by Debdutta Das A Thesis submitted to The Faculty of The College of Engineering and Computer Science In Partial Fulfillment of the Requirements for the Degree of Master of Science Florida Atlantic University Boca Raton, Florida December 2009 ACKNOWLEDGEMENT I would like to thank Dr. Hassan Mahfuz for his direction, assistance and guidance in the preparation of this thesis. I also wish to thank the members of the supervisory committee, Dr. Palaniswamy Ananthakrishnan and Dr. Francisco Presuel-Moreno, for their valuable recommendations and suggestions. Financial support in the form of a research assistantship from the Office of Naval Research is gratefully acknowledged. I would like to thank my nanolab members for their valuable support. I would sincerely thank my family for their advice and support. Lastly, I would like to acknowledge a sincere appreciation of the above mentioned for the experience that is the foundation of future endeavors. iii ABSTRACT Author: Debdutta Das Title: Reinforcement of Syntactic Foam with SiC nanoparticles Institution: Florida Atlantic University Thesis Advisor: Dr. Hassan Mahfuz Degree: Master of Science Year: 2009 In this investigation, polymer precursor of syntactic foam has been reinforced with SiC nanoparticles to enhance mechanical and fracture properties. Derakane 8084 vinyl ester resin was first dispersed with 1.0 wt% of SiC particles using a sonic cavitation technique. In the next step, 30.0 wt% of microspheres (3M hollow glass borosilicate, S-series) were mechanically mixed with the nanophased vinyl ester resin, and cast into rectangular molds. A small amount of styrene was used as dilutant to facilitate mixing of microspheres. The size of microspheres and SiC nanoparticles were 20-30 μm and 30-50 nm, respectively. Tension, compression, and flexure tests were conducted following ASTM standards and a consistent improvement in strength and modulus within 20-35% range was observed. Fracture toughness parameters such as KIC and GIC were also determined using ASTM E-399. An improvement of about 11-15% was observed. iv Samples were also subjected to various environmental conditions and degradation in material properties is reported. v REINFORECEMENT OF SYNTACTIC FOAM WITH SiC NANOPARTICLES LIST OF FIGURES…………………………………………………….…………….. viii LIST OF TABLES……………………………………………………………………. xi CHAPTER 1. INTRODUCTION…………………………………………………....... 1 1.1 Literature Review…………………………………………………………………… 5 1.2 Scope of Thesis…………………………………………………………………….. 9 CHAPTER 2. MATERIALS AND SYNTHESIS…………………………………… 11 2.1 DERAKANE 8084…………………………………………………………………. 11 2.2 Glass Microballons S series…………………………………………………………11 2.3 Styrene………………………………………………………………………………13 2.4 MEKP……………………………………………………………………………… 14 2.5 Cobalt Naphtenate…………………………………………………………………. 15 2.6 Silicon Carbide…………………………………………………………………….. 16 2.7 Synthesis of syntactic foam………………………………………………………... 18 2.71 Determination of the right ratio………………………………………………… 18 2.72 Procedure……………………………………………………………………….. 19 2.8 Density of syntactic foam………………………………………………………….. 21 CHAPTER 3. MICROSTRUCTURAL AND MECHANICAL CHARECTERIZATION……………………………………………………………..23 vi 3.1 SEM Analysis…………………………………………………………………… 24 3.2 Mechanical characterization……………………………………………………….. 25 3.21 Compression Test………………………………………………………………. 25 3.22 Flexure Test…………………………………………………………………….. 27 3.23 Tension Test…………………………………………………………………….. 28 3.24 Fracture Toughness Test…………………………………………………………30 CHAPTER 4. DURABILITY OF SYNTACTIC FOAM UNDER SALT WATER ENVIRONMENT ………………………….……………………….33 4.1 Moisture absorption of syntactic foam…………………………………………… 34 4.11 Environmental Exposure………………………………………………………. 35 4.2 Compression Test………………………………………………………………… 36 CHAPTER 5. RESULTS AND DISCUSSION……………………………………..37 5.1 Compression Test ASTM C-365…………………………………………………..37 5.2 Flexure Test………………………………………………………………………...40 5.3 Tension Test……………………………………………………………………….. 43 5.4 SENB Test………………………………………………………………………… 47 5.5 Durability Test……………………………………………………………………. 50 5.51 Compression test on wet specimens…………………………………………….55 CHAPTER 6. SUMMARY…………………………………………………………. 59 REFERENCES……………………………………………………………………… 61 vii LIST OF FIGURES Figure 1: Pictographic representation of syntactic foam……………………………… 5 Figure2: SEM of syntactic foam……………………………………………………… 6 Figure3. Glass bubbles ………………………………………………………………. 12 Figure 4: SEM of S38 microspheres…………………………………………………..12 Figure 5: Molecular structure of styrene……………………………………………....14 Figure 6: Molecular alignment in MEKP……………………………………………. 15 Figure 7: Co-NAP……………………………………………………………………. 15 Figure 8: SiC crystals………………………………………………………………… 17 Figure 9: Flow Diagram……………………………………………………………… 19 Figure 10: Homogenization ………………………………………………………….. 20 Figure 11: Sonication…………………………………………………………………. 20 Figure 12: Mechanical mixing procedure ……………………………………………. 21 Figure 13: Casting in the mould………………………………………………………. 21 Figure 14: Two phased structure ……………………………………………………... 22 Figure 15: Three phased structure…………………………………………………….. 22 Figure 16: Scanning electron microscope (SEM)…………………………………….. 23 Figure 17: NEAT SPECIMEN ……………………………………………………… 24 Figure 18: NANO SPECIMEN………………………………………………………. 24 Figure 19: Orientation and size of specimen………………………………………….. 26 viii Figure 20: Dimension of flexure specimen……………………………………………. 27 Figure 21: Dimension of the tensile specimen……………………………………….... 29 Figure 22: Testing Procedure………………………………………………………….. 30 Figure 23: Dimension of the SENB specimen………………………………………… 31 Figure 24: Test Setup………………………………………………………………….. 32 Figure 25: Test Setup for compression…………………………………………………36 Figure 26: Stress –strain curve for compression test………………………………….. 38 Figure 27: Typical formation of crack during compression........................................... 39 Figure 28: Tested specimen…………………………………………………………… 40 Figure 29: Load displacement curve for flexure test………………………………….. 41 Figure 30: Tested Specimen…………………………………………………………... 42 Figure 31: Failure sequence of the syntactic foam……………………………………. 42 Figure 32: Graphical representation of Tension Test…………………………………. 44 Figure 33: Modulus of strength………………………………………………………...45 Figure 34: Tested Tensile Specimen………………………………………………….. 46 Figure 35: Load transfer on microspheres upon tensile loading……………………… 46 Figure 36: SEM picture of the fracture surface of the syntactic foam………………... 49 Figure 37: Graphical representation of SENB Test……………………………………47 Figure 38: Graphical analysis of water uptake……………………………………….. 53 Figure 39: Neat specimen in SWT……………………………………………………. 54 Figure 40: Comparison of Neat and Nano specimen in SW………………………….. 54 Figure 41: Comparison of Neat and Nano specimen in SWT………………………... 54 Figure 42: Comparison of Neat and Nano in HT…………………………………….. 55 ix Figure 42: Stress strain curves of compression test on wet specimens…….………. 57 x LIST OF TABLES Table 1: Resin Properties…………………………………………………………. 11 Table 2: Microspheres Property…………………………………………………... 13 Table 3: Dilutant Property………………………………………………………… 14 Table 4: Nanoparticles Property…………………………………………………... 18 Table 5: Foam density…………………………………………………………….. 21 Table 6: Compression test results………………………………………………… 37 Table 7: Average of compressive test results…………………………………….. 38 Table 8: Determination of flexural test results…………………………………… 41 Table 9: Average of flexural test results………………………………………….. 41 Table 10: Representative of tension test results…………………………………... 43 Table 11: Average of tension test results………………………………………….. 43 Table 12: Fracture toughness test results…………………………………………. 48 Table 13: Average of SENB test results………………………………………….. 48 Table 14: Water uptake in week 1&2…………………………………………….. 51 Table 15: Water uptake in week 3&4…………………………………………….. 51 Table 16: Demonstration of moisture retention capacity………………………… 52 Table 17: Water uptake% in foams………………………………………………. 53 Table 18: Compression Test Results for wet neat specimens……………………. 56 Table 19: Compression Test Results for wet nano specimens…………………… 56 xi Table 20: Comparison under compressive loading……………………………57 xii CHAPTER 1: INTRODUCTION The word syntactic is derived from the word “syntax” whose implied meaning is to piece together. Syntactic foams are examples of particulate composite materials. According to American Society for Testing and Materials [1], syntactic foam is defined as a ―material consisting of hollow spherical fillers in a resin matrix. As per its definitions syntactic foam consists of hollow glass spheres known as microballoon that are coagulated in a binder phase, usually in a polymeric resin system. Syntactic foam are classified as composite materials which are synthesized by filling a metal, polymer or ceramic matrix with hollow particles called microballons.The hollow particles present in syntactic foams effectively results in lowering the density ,increasing the strength, lowering the thermal expansion coefficient and in special cases it also results in radar or sonar transparency. The matrix resin can be chosen from a wide range of thermoplastic and thermosetting resins depending on the service conditions. Similarly cenospheres of polymer, ceramic or metal can be chosen. There are other parameters which can be adjusted like the volume fraction of the matrix and cenospheres in the structure. These are two significant methods for changing the density of syntactic foams which directly influences their properties. Composite material can be classified as a construction material that consists of two or more different materials;