Based Composite Vulcanized Fiber

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Direction-dependent mechanical characterization of cellulose-based composite vulcanized ﬁber

Article in Materials Testing · October 2016 DOI: 10.3139/120.110929

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Ronja Scholz Jenni Engels Technische Universität Dortmund Interdisciplinary Centre for Advanced Materials Simulation

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The user has requested enhancement of the downloaded file. MECHANICAL TESTING 813 Direction-dependent mechanical characterization of cellulose- based composite vulcanized fiber

Ronja Scholz, Roman-Marius Vulcanized fiber is a macromolecular cellulose-based composite material Mittendorf, Dortmund, Jenni Kristin manufactured using the parchmentizing process. The cellulose is pro- Engels, Alexander Hartmaier, duced from the chemical digestion of plant-based raw materials (wood, Bochum, Bernd Künne and Frank cotton) or textile waste. Chemical additives used during manufacturing Walther, Dortmund, Germany are completely removed. After the process, vulcanized fiber possesses improved properties concerning mechanical strength and abrasion as Article Information well as corrosion resistance in comparison to its raw materials. Concern- Correspondence Address ing its economic life cycle assessment, low density, electrical insulating MSc Ronja Scholz Institute for Design and Materials Testing (IKW) capability and balanced properties, vulcanized fiber has a potential, up Department of Materials Test Engineering (WPT) to now unused, as a light and renewable structural material for applica- TU Dortmund University Baroper Str. 303 tions in automotive or civil engineering industries. Research activities D 44227 Dortmund, Germany concerning the mechanical properties are insufficient and existing E-mail: [email protected] standards are out-of-date. In this work, for the first time a direction-de- Keywords pendent characterization of the process-related anisotropic mechanical Resource efficiency, lightweight construction, cellulose basis, vulcanized fiber, anisotropy, properties of the material is realized with the aim to formulate an ade- material model quate material model for numerical simulations in the next step.

Increasing social consciousness about envi- was firstly developed in the mid-19th cen- tion, the degradation of cellulose has to be ronment, finite nature of fossil fuels and gen- tury. It is made of absorbent and unsized limited in time. Another important param- eral waste recycling as well as increasing po- special papers which are joined by a merg- eter is the temperature of the parchmentiz- litical requests for resource-efficient produc- ing process into a homogenous material by ing solution, usually, it is in the range of 30 tion processes and alternative resource-saving adding a parchmentizing solution. Predom- to 65 °C. After bonding, the parchmentiz- material concepts are important tasks of the inantly, a zinc chloride solution (ZnCl2) is ing solution is leached out in a multistage 21st century. Vulcanized fiber as one of the used for parchmentizing. Another alterna- process by using osmotic forces. Finally, oldest plastics based on renewable resources tive is sulfuric acid (H2SO4). The parchmen- vulcanized fiber is dried and smoothed. The has proven to be an appropriate substitute. tizing solution acts as a catalyst. During the thickness of the resulting product is de- The aim of the authors is the reactivation of process the crystalline structure of cellu- fined by the amount of single paper layers the industrial interest in vulcanized fiber as lose 1 is converted into cellulose 2 which is which are added at the beginning of the an alternative resource-saving material con- an irreversible and pure physical process. continuous manufacturing process [1]. Fig- cept for industrial applications. Therefore At the microscopic level, swelling and ure 1 shows the modification of cellulose comprehensive scientific studies are re- shortening of cellulose fibers can be identi- caused by parchmentizing during the man- quired. In the present study, tensile and com- fied. The fiber length is reduced by round ufacturing process, and it was analyzed us- pression tests were performed to investigate about a quarter. Simultaneous to the struc- ing a scanning electron microscopy (SEM). mechanical properties of vulcanized fiber tural conversion, a hydrolytic degradation Until 1930, vulcanized fiber had been which can be used to estimate the perfor- of cellulose starts. Cellulose chains are split used in many fields of application because of mance capability and for numerical simula- and low-molecular structures are formed. its good material properties. As lightweight tions of its deformation behavior. These structures are essential for a repo- construction material (ρ = 1.10 to 1.45 g·cm- lymerization process which is necessary to 3), it is high abrasion-resistant, physiologi- Material relink single cellulose fibers and to link cally harmless, electrically insulating, spark single paper layers to one homogeneous extinguishing and resistant to sustained Vulcanized fiber material is fully based on material called vulcanized fiber. To avoid a temperatures of 120 to 160 °C. Further, vul- the renewable raw material cellulose and loss of mechanical strength by saccharifica- canized fiber offers versatile processing pos-

58 (2016) 10 © Carl Hanser Verlag, München Materials Testing

a) b) For investigations in x-, y- and xy-directions, specimen geometry type 1 B is used (see Figure 2). For a better understanding, Figure 3 shows a schematic of the specimen locations in vulcanized fiber sheets, horizontal (x, y, xy) and perpendicular (z) in relation to the manufacturing direction and fiber orientation, respectively, for tensile tests. For tests in z-direction, a suitable specimen geometry has to be chosen because of Figure 1: SEM micrographs of cellulose fibers, a) raw paper, b) vulcanized fiber limited vulcanized fiber sheet thickness available on the market with a maximum of sibilities, for example, by milling, drilling, cations, i. e., fiber orientations according to 16 mm. To increase the segment for sam- forming, bending, stamping and varnishing. manufacturing direction, are performed. pling, several sheets of finished and homo- With upcoming petrochemical plastics, it Hygroscopicity. Further, hygroscopic geneous vulcanized fiber were adhesively has been replaced from the market. Today properties have to be considered for cellu- bonded. This results in at least two glued only a few particular applications exist and lose products like vulcanized fiber. This im- areas within the total specimen length L. there is a big lack of knowledge about the plies a moisture content which depends on Four possible geometries according to DIN characteristics of the material [2, 3]. the climatic conditions of the environment. EN ISO 20753 were investigated in pre- Anisotropy. For scientific research, it Moisture content increases with increasing tests to prove their functionality. Thereby, has to be taken into account that vulcan- relative humidity as well as decreasing tem- three designs were not considered because ized fiber is anisotropic. Cellulose fibers in perature and has a significant impact on ma- of occurring failure in the glued areas. Fi- paper layers are preferably orientated in terial properties and dimension stability of nally, three homogeneous vulcanized fiber manufacturing direction due to the produc- vulcanized fiber. Previous tests showed that sheets were layered above each other, one

tion process [4-6]. This longitudinal direc- high material moisture has a detrimental ef- with L2 = 15 mm in the center and two with tion of cellulose fibers in vulcanized fiber fect on mechanical strength properties, like L1 = 8 mm at each top, and milled to a final sheets is defined as x-direction, while the ultimate tensile strength UTS and Young’s specimen thickness of t = 4 mm. This ar- cross direction, perpendicular to x-direc- modulus E. On the other hand, it has a ben- rangement proved to be practical because tion, is termed as y-direction. In addition, eficial effect on the flexibility [7, 8]. adhesive joints are not located in the gauge

due to parchmentizing and merging of sin- Thus an important prerequisite for the length of the specimen L0 = 8 mm and frac- gle paper layers, different material proper- capabilities and results interpretation of ture could be initiated in pure material (L2), ties are expected perpendicular to the xy- vulcanized fiber is an exactly defined test as shown in Figure 4. plane. This z-direction specifies the layer climate. For the following studies, a testing For performing compression tests, structure properties. condition of room temperature RT and rela- DIN 7738 references to DIN EN ISO 604 for Focus of research is the analysis of tive humidity φ = 40-50 % was ensured. The polymers. By applying this standard, the quasi-static material properties of vulcan- tests were performed with homogeneous thickness of the specimen would be ized fiber in x-, y-, xy-(diagonal-) and z-di- vulcanized fiber material (brand name t ≤ 1 mm which is technically difficult to rections. For this reason, tensile and com- “Hornex”) provided by Ernst Krueger, realize and unfunctional. So, a cube geom- pression tests with different specimen lo- Geldern. etry with side lengths of L = 10 mm was chosen. Compression tests concerning x-, a) b) Experimental procedure y- and z-directions were performed with conditions comparable to tensile tests [9]. The anisotropic mechanical properties of Figure 5 shows the load directions accord- vulcanized fiber have to be tested sepa- ing to the manufacturing direction and rately according to DIN 7738 standard fiber orientation, respectively. from 1959, which references to DIN EN ISO All tests were performed using a univer- 527, defining the determination of tensile sal testing machine (Shimadzu AG-X, . -3 -1 properties of plastics. For tests perpendicu- Fmax = 100 kN) with a strain rate ε = 10 s . lar to the layered structure, i. e., in z-direc- To avoid surface impairment, a video exten- tion, there is no valid standard available. someter (Shimadzu TRViewX) was applied

Figure 3: Schematic of Figure 2: Specimen geometry according to specimen locations for DIN EN ISO 527 for tensile tests in x-, y- and tensile tests xy-directions, a) technical drawing (data in mm, manufacturing tolerances according to ISO 2768-m), b) test setup

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a) Hooke’s law cannot be used to determine observed. In the fracture pattern in Fig- Young’s modulus E. Following DIN EN ISO ure 8c (z2), there seem to be areas which 527, for comparability, the tensile modulus are bonded stronger than others. This -4 -3 b) ET between ε1 = 5∙10 and ε2 = 2.5∙10 was proves the assumption of scattering in z- determined for all directions (see Ta- direction as a consequence of an inconsist- Figure 4: Specimen geometry for tensile tests ble 1a). Therefore, significant differences ent bonding process. in z-direction, a) technical drawing in E according to specimen location, with Under compressive stress, the load flat- (data in mm, manufacturing tolerances T minimum values of 2,000 ± 400 MPa for tens the specimen in z-direction in com- according to ISO 2768-m), b) test setup specimens in z-direction and maximum parison to initial condition (see Figure 9a). values of 6,300 ± 340 MPa in x-direction, In contrast to this mainly ductile material for contact-free measurement of material can be evaluated. The scatter in results for deformation, a mainly brittle material be- strain as response to applied load. For sta- the z-direction is greater compared to havior is detected for tests in x- and y-direc- tistical validation, five specimens were other directions which can be justified by tions (see Figure 9b). tested for each direction [9, 10]. inconsistent bonding between raw-paper The previous results of mechanical and layers in the parchmentizing process. Be- microscopic investigations prove higher

Results and discussion sides, the compressive moduli EC between strength of vulcanized fiber compared to 2,250 ± 400 MPa in z-direction and synthetic plastics, although it is not effec- The ultimate tensile strength UTS of vul- 5,860 ± 340 MPa in x-direction are given tively fiber-reinforced. Cellulose fibers are canized fiber varies with the specimen lo- for vulcanized fiber, as can be seen in Ta- only oriented predominantly in manufac- cation according to manufacturing direc- ble 1a. Furthermore, for comparison is- turing direction what affects the mechani- tion. Tensile stress (σT) – total strain (εt) sues, the properties of common plastics cal properties considerably. Additionally, curves are plotted in Figure 6. The mate- (see Table 1b) and woods (see Table 1c) the application temperature of vulcanized rial shows a maximum tensile strength in under tensile loading are quoted. fiber is much higher (120-160 °C compared x-direction UTSx = 90 MPa because of lon- Anisotropic behavior of vulcanized fiber to 70-90 °C), as shown in Table 1b. Com- gitudinal fibers bear complete load. Y- and is also observable in compression tests, see pared to wood (see Table 1c), vulcanized xy-directions show lower values in the compressive stress (σC) – total strain (εt) fiber reaches similar ultimate tensile range of 60 MPa, since lateral loads (com- curves in Figure 7. Ultimate compressive strengths in fiber (x-) direction, half of pared to manufacturing direction) load the strength UCS and total strain εt are greater Young’s modulus and two- to three-time the vulcanized fiber matrix, which is softer compared to values obtained in tensile density. Greater total strain values under than longitudinal fibers. Concerning these tests. Z-direction leads to UCSz = 350 MPa [5] could be a crucial benefit of vulcanized -2 three horizontal specimen locations, a pro- at Epsilont = 11.3·10 , wehereas x- and y- fiber for the production of complex geome- nounced elastic material behavior up to a directions show a maximum compressive tries. stress level of at least 40 MPa and follow- strength in the range of 225-230 MPa at ing plastic deformation until maximum to- failure strains of 18.0·10-2 to 20.0·10-2. Af- -2 -2 tal strains of εt = 9.8·10 to 10.8·10 for ter an almost linear elastic loading in x- -2 x- and y-directions as well as εt = 14.2·10 and y-directions, there is a yield in the for the xy-direction can be observed. A range of 80-90 MPa with a plateau until yield strength of about 50 MPa only ap- 8·10-2 followed by strain hardening. pears for specimens in xy-direction. Z- Microscopic investigations were carried specimens located perpendicular to manu- out using an optical microscope (Keyence facturing direction show a rubber-like de- VHX (500F)). The fracture patterns vary in formation behavior according to DIN EN dependence of the specimen locations. For ISO 527 but with much smaller deforma- tensile-loaded x-direction, cellulose fibers tions of about 0.4·10-2 compared to hori- are arranged longitudinally and emerge at zontal specimens. Further, strength values the position of fracture (see Figure 8a). For of the layered structure are in a consider- specimens in y-direction, the fibers are Figure 6: Stress-strain curves for tensile tests in able lower range of UTSz = 8 MPa. Parch- much more disordered at the fracture posi- mentizing results in different binding tion (see Figure 8b) which results in 30 % x-, y-, xy- and z-directions mechanisms which seem to be stronger lower strength values. In z-direction, per- horizontal to manufacturing direction. pendicular to paper layers bonded in parch- Concerning the deformation behavior in mentizing process, a delamination of paper z-direction, no ideal elastic zone exists, so layers within vulcanized fiber sheet can be

a) b) c)

Figure 7: Stress-strain curves for compression Figure 5: Schematic of stress directions in compression tests, a) x-direction, b) y-direction, c) z-direction tests in x-, y- and z-directions

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a) With the help of an even extended ex- Tensile Compression perimental basis, it may be possible to con- Vulcanized fiber sider the influence of temperature and rel- x xy y z x y z ative humidity on the maximum applicable UTS resp. UCS 83 ± 2.5 59 ± 1.0 58 ± 3.0 7.5 ± 2.2 230 ± 23 220 ± 18 350 ± 8 (MPa) tensile and compression stresses in the developed material model. Further experi- ET resp. EC 6,300 ± 4,400 ± 4,600 ± 2,000 ± 5,860 ± 4,470 ± 2,250 ± (MPa) 340 100 140 400 340 235 30 mental investigations are planned to deter- ρ mine biaxial load conditions. In addition to 1.45 (g∙cm-3) the biaxial tension and compression load T appl. 120-160 case, shear stress will be characterized as (°C) well. A cooperation of experimental and numerical work will lead to a comprehen- b) c) sive understanding of vulcanized fiber. Plastics PA6 PE-LD ABS POM Wood Softwood (spruce) Hardwood (oak) UTS UTS 50 - 80 9 50 64 90 90 Acknowledgement (MPa) (MPa) E 1,500 - E 200 2,400 3,000 13,000 11,000 (MPa) 3,000 (MPa) The authors gratefully acknowledge the ρ ρ support by Dr. Manfred Joseph, Ernst 1.14 0.92 1.05 1.41 0.65 0.43 (g∙cm-3) (g∙cm-3) Krüger GmbH & Co. KG, Geldern, Germany, T T by providing the investigated materials. appl. 90 70 80 90 ignit. 270 280 (°C) (°C) References Table 1: Ultimate tensile strength UTS, ultimate compression strength UCS, Young’s modulus E, density ρ, application temperature T and ignition temperature T of a) vulcanized fiber [9, 10], b) common appl. ignit. 1 G. M. Swallowe: Mechanical Properties and plastics [11], c) wood [12] Testing of Polymers: An A-Z Reference, Springer, The Netherlands (2013) 2 T. Taylor: Improvement in the Treatment of Pa- Conclusions and outlook tests show a maximum compressive strength per and Paper-Pulp, U. S. Patent 114, 880 in z-direction. These results are a basis to (1871) The anisotropic behavior of vulcanized understand the deformation behavior of 3 W. F. Brown: Vulcanized Fibre – An Old Mate- fiber was comprehensively investigated in vulcanized fiber with respect to direction- rial with a New Relevancy, NVF Company, direction-dependent tensile and compres- dependent loads. Yorklyn, Delaware, USA (1999) 4 B. Penning, F. Walther: Microstructure-orien- sion tests, whereas anisotropy is more sig- As vulcanized fiber is characterized by tated evaluation of the fatigue behavior of nificant under tensile loads. Tensile tests in different deformation behavior concerning technical vulcanized fiber out of cellulose fib- z-direction, perpendicular to manufactur- the specimen location depending on the ers, H.-J. Christ: Materials Testing 2013 – Im- ing direction, lead to 8- to 11-times lower manufacturing direction, a broad experi- provements in Materials Testing for Research tensile strengths and 22- to 31-times lower mental database is required to simulate the and Practice, Stahleisen Verlag, Germany total strains in comparison to x-, y-, and xy- reaction of the material in relation to ap- (2013), pp. 169-174 (in German) directions, but they enable the evaluation plied mechanical loads. A first approach 5 S. Myslicki, M. Ortlieb, G. Frieling, F. Walther: High-precision deformation and damage devel- of the quality of parchmentizing process. will try to describe the elastic behavior opment assessment of composite materials by Inconsistent bonding of layers through the with a simple orthotropic, but linear rela- high-speed camera, high-frequency impulse parchmentizing process was observed in tion. Moreover, plasticity will be described and digital image correlation techniques, microscopic investigations of the fracture by a Drucker-Prager model which is able to Materials Testing 57 (2015), No. 11-12, pattern. Results obtained in compression consider tension/compression anisotropy. pp. 933-941 DOI:10.3139/120.110813 6 R. Mittendorf, B. Penning, B. Kuenne, F. a1) b1) c1) Walther: Property und joining technology orientated qualification of the ”new“ resource-efficient fiber-lightweight material vulcanized fiber, Materials in Manufacturing (2013), No. 4, pp. 10-11 (in German) 7 C. Fiedler Bremer, R. Scholz, S. Myslicki, P. Starke, C., Boller, F. Walther, M. Krause: NDT-based characterization of timber and

a2) b2) c2) a) b)

Figure 9: Fracture patterns in compressions tests, a) initial condition (i. c.) and z-direction, Figure 8: Fracture patterns in tensile tests, a) x-direction, b) y-direction, c) z-direction b) x- and y-directions

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vulcanized fiber for civil infrastructure, Proc. Bochum, Germany and Director at the Interdiscipli- has been Professor in the Department of Machine of the International Symposium Non-Destruc- nary Center for Advanced Materials Simulation Elements (ME) at TU Dortmund University, Ger- tive Testing in Civil Engineering NDT-CE, (ICAMS). Before this appointment, he was Profes- many. Besides, he is an author of specialist litera- Berlin, Germany (2015), pp. 1-11 sor of Materials Science at Friedrich Alexander ture in the field of design. 8 D. Dumke, B. Penning, B. Kuenne, F. Walther: University Erlangen-Nuremberg, Germany from Prof. Dr.-Ing. Frank Walther, born in 1970, Influence of deformation speed and moisture 2005 to 2008. Prior to this position, he headed the studied Mechanical Engineering, majoring in content on the quasi-static deformation behav- group “Nanostructured Materials” in the Depart- Materials Science and Engineering at TU Kaiser- ior of technical vulcanized fiber, Materials Test- ment “Theory of Mesoscopic Phenomena” of Prof. slautern University, Germany, from 1992 to 1997. ing 55 (2013), No. 4, pp. 276-284 (in German) Huajian Gao at the Max Planck Institute for Metals There, he finished his PhD on the fatigue assess- DOI:10.3139/120.110435 Research in Stuttgart, Germany. This is the same ment of highly-loaded railway wheel steels at the 9 G. Tully: Mechanical Characterization of institute where he worked on his PhD thesis with Institute of Materials Science and Engineering Vulcanized Fiber Material, Bachelor Thesis, In- the topic “Modeling the brittle-to-ductile transition (WKK) in 2002. From 2002 to 2008, he headed the stitute for Design and Materials Testing (IKW), in tungsten single crystals”, which was finalized in research group Fatigue Behavior at WKK and fin- TU Dortmund University, Germany (2015) (in 1999. The thesis has been awarded the Otto Hahn ished his postdoctoral qualification (habilitation) German) Medal of the Max Planck Society. In between his in Materials Science and Engineering in 2007. Af- 10 J. Berges: Investigation of the quasi-static stays at the Max Planck Institute in Stuttgart, he terwards, he joined Schaeffler AG in Herzogenau- properties of the cellulose-based composite spent three years in industrial research in respon- rach, Germany, and took responsibility for Public material vulcanized fiber in z-direction, sible functions as project leader and group leader. Private Partnership within Corporate Develop- Summary of Scientific Project Work, Institute His academic career started at the University of ment. Since 2010, he has been Professor for Mate- for Design and Materials Testing (IKW), Kaiserslautern, Germany, where he obtained his rials Test Engineering (WPT) at TU Dortmund Uni- TU Dortmund University, Germany (2015) Physics Diploma in 1995 (equivalent to MSc). versity, Germany. His research portfolio includes (in German) The focus of his research lies on the investigation determination of process-structure-property rela- 11 S. Lampman: Characterization and Failure of deformation and fracture mechanisms of mul- tionships, investigation of fatigue behavior form Analysis of Plastics, ASM International, tiphase materials, mainly with scale-bridging mod- the LCF to VHCF range under temperature and Materials Park, Ohio, USA (2003) eling and experimental methods. Besides his aca- corrosion environments, application of physical 12 S. J. Record: Mechanical Properties of Wood, demic activities, he is Vice Chairman of the Ger- measurement techniques and condition monitor- J. Wiley & Sons, New York, USA (1914) man Materials Society (Deutsche Gesellschaft für ing systems as well as damage accumulation and Materialkunde) in which he had organized the pro- (remaining) lifetime calculation approaches with Bibliography gram for young scientists from 2010 to 2014. regard to mechanism-oriented modeling of materi- Prof. Dr.-Ing. Bernd Künne, born in 1956, stud- als behavior. Besides, he is engaged in various DOI 10.3139/120.110929 ied Mechanical Engineering at Paderborn Univer- committees, e. g., as member of the Board of Ger- Materials Testing sity, Germany. There he finished his PhD on the man Materials Society (DGM) and member of the 58 (2016) 10, pages 813-817 switching characteristic of friction clutches at the Scientific Association of Materials Engineering © Carl Hanser Verlag GmbH & Co. KG Laboratory for Design Theory in 1984. In 1990, he (WAW). He has published more than 140 reviewed ISSN 0025-5300 was appointed Professor of Design Theory and CAD papers and conference proceedings and maintains at University Emden/Leer, Germany. In 1993, he close scientific contact with institutions and indus- The authors of this contribution finished his postdoctoral lecture qualification (ha- tries in the materials science and engineering field bilitation) in cost-conscious design. Since 1993, he worldwide. MSc. Ronja Scholz, born in 1987, studied Sales En- gineering and Product Management with specialization in Materials Engineering at Ruhr-University Abstract Bochum, Germany. After her master thesis, she has been working as a scientific assistant at the Insti- Richtungsabhängige Materialcharakterisierung von cellulosebasierter tute for Design and Materials Testing (IKW), De- partment of Materials Test Engineering (WPT), at Vulkanfiber. Vulkanfiber ist ein abgewandeltes makromolekulares Natur- TU Dortmund University, Germany. produkt, welches durch Pergamentierung von Spezialpapieren auf Basis Her research focus is on fatigue and fracture of re- von Holz- oder Baumwollcellulose hergestellt wird. Der Rohstoff ist Cellu- source-efficient composite materials. Dr.-Ing. Roman-Marius Mittendorf, born in lose, deren Gewinnung über einen chemischen Aufschluss pflanzlicher 1987, studied Mechanical Engineering at TU Dort- Rohstoffe oder durch Recycling von Textilabfällen realisiert wird. Die hier- mund University, Germany. Since 2012, he has been working as a scientific assistant at the Insti- für verwendeten chemischen Zusätze werden wieder vollständig aus dem tute for Design and Materials Testing (IKW), De- Material entfernt. Nach diesem Prozess zeichnet sich Vulkanfiber durch partment of Mechanical Engineering (ME), TU verbesserte Eigenschaften hinsichtlich mechanischer Festigkeit sowie Ab- Dortmund University. His research focus is on ex- amining and designing products made of renewa- rieb- und Korrosionsbeständigkeit im Vergleich zu den verwendeten Roh- ble raw materials. stoffen aus. Hinsichtlich der günstigen Ökobilanz, geringen Materialdichte, MSc. Jenni Kristin Engels, born in 1987, studied Mechanical Engineering with specialization in Mi- elektrischen Isolierfähigkeit und ausgewogenen mechanischen Materialei- cro-Engineering and Materials Science and Engi- genschaften, ergibt sich für Vulkanfiber ein bisher ungenutztes Potenzial neering at Ruhr-University Bochum, Germany. She is currently working as a doctoral candidate at the als leichter und nachwachsender Konstruktionswerkstoff für den Einsatz in Chair of Micromechanical and Macroscopic Mode- der Automobil- und Bauindustrie. Die mechanischen Kennwerte sind for- ling (MMM) at ICAMS, Ruhr-University Bochum. schungsseitig bislang unzureichend beschrieben und bestehende Richtli- Her research focuses on the experimental and numerical characterization of tempered martensite nien veraltet. In dieser Arbeit wird erstmals eine richtungsabhängige Cha- and vulcanized fiber. rakterisierung der prozessbedingt anisotropen mechanischen Eigenschaf- Prof. Dr. Alexander Hartmaier is currently Pro- fessor of Materials Science (Chair in Micromechan- ten von Vulkanfiber vorgenommen. Die experimentell ermittelten Daten ical and Macroscopic Modeling) at Ruhr-University sollen die Generierung eines numerischen Werkstoffmodells ermöglichen.

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