A finite element analysis of auxetic composite fabric with rotating square structure

The auxetic property of macro-porous rotating square structure has been investigated by many using either experimental or numerical approaches. Given the low breaking strength of the typical rotating square structure, it was proposed to employ an elastic base material to the cellular auxetic structure to improve its strength while maintaining its auxetic behavior in our previous study. Despite the experimental studies conducted, a numerical analysis is needed to explain the auxetic effect found in the produced laminated fabrics. In this paper, the auxetic properties of the 2-layer laminated system were simulated using the finite element approach and the effects of the modulus difference between the frame and the base were discussed. The main findings are (1) the simulated results based on a simplified model are broadly consistent with experimental ones under low tensile strain ranges; (2) the initial modulus of the frame material in the stretched direction and that of the base material in the lateral direction are critical to the generation of auxetic effect in the laminated system; (3) at least a 10-time difference of the modulus between the frame and the base materials is required to generate an auxetic effect in the 2-layer laminated structure and the overall auxetic property is increased by enlarging difference of the modulus within a tolerance. It is expected that this research could provide an instructive reference for the future design of auxetic materials.