PSI - Issue 17

Michał Kwietniewski et al. / Procedia Structural Integrity 17 (2019) 58–63 Michał Kwietniewski / Structural Integrity Procedia 00 (2019) 000 – 000

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5 Summary The results of the analyses showed that the increasing value of the Young's modulus of the warp causes problem in the free bending of the HAY. The effect of this is the minimalize of the auxetic effect, which caused that the model tends to positive value of Poisson ratio. For the applied material values of the core (TPEE elastomer) and the wrap (Kevlar), the limit of the Young's modulus of the matrix material is about 5 GPa. Above this value, the model becomes non-auxetic. However, one should also remember about the used generalizations and simplifications adopted for analyses. The accurate determination of Poisson's ratio is possible only after simulations involving higher number of auxetic threads in the matrix. The use of a material model with a linear characteristic allowed modifying the material behaviour by one parameter (the Young's modulus in this case). It also caused limitations. It was not possible to obtain larger strain when stretching, due to problems with convergence. In such cases, it is required to use dedicated material models that are based on constitutive models for rubber materials. Although isotropic materials with linear characteristics were used for the analysis, a non-linear response was obtained. Even with small deformations, a change in cross-section caused a deviation from linearity. Considering the model consisting of materials with different stiffness values, as in the discussed analyses, the Arbitrary Lagrange-Euler method can be used to investigate the course of the characteristic over the entire stretching range. Acknowledgements The research was conducted as a part of young scientists and PhD students development project RMN No. 955/2018 titled “ Experimental and numerical studies of energy consumption of composite structures reinforced by auxetic fabrics" sponsored by Military University of Technology. Alderson K., Alderson A., Smart G., Simkins V., Davies P., 2002. Auxetic polypropylene fibres: part 1 – manufacture and characterization, Plast Rubber Compos 31, 8, 344 – 349. Hook P., 2011. Uses of auxetic fibres, US Patent Number 8002879 B2. Kevlar Aramid Fiber, Technical Giude. L. S. T. Corporation, 2002. LS-dyna keyword user's manual volume II LS- dyna r8.0,” (LSTC). L. S. T. Corporation, 2002. LS-dyna keyword user's manual volume I LS- dyna r8.0,” (LSTC). Piechna, A., 2011. Siatka obliczeniowa w numerycznej mechanice płynów. Proj ektowanie i konstrukcje inżynierskie, 6, 45. Sloan, M. R., Wright, J. R., Evans, K. E., 2011. The helical auxetic yarn – A novel structure for composites and textiles; geometry, manufacture and mechanical properties. Mechanics of Materials, 476-486. Zhang, Y., Wu, W., Wu, R., Luo, Q., Wang, Z., 2014. The flame retarding mechanism of the novolac as char agent with the fire retardant containing phosphorous-nitrogen in thermoplastic poly(ether ester) elastomer system. Polymer Degradation and Stability, 105, 166-177. Zhong, Z., Li, M., Zhang, L., Zhang, X., Zhu, S., Wu, W., 2015. Adding the combination of CNTs and MoS2 into halogen-free flame retarding TPEE with enhanced the anti-dripping behavior and char forming properties. Thermochimica Acta(613), 87-93. References: