Finite element computation with anisotropic hyperelastic model considering distributed fibers for artificial and natural leather used in sports

Materials such as natural leather and artificial leather are some of the most important materials in sports. Natural leathers have been widely used for sports equipment. Currently, artificial leathers are also often used in sports as an alternative to natural leathers. However, the structure of both artificial and natural leather materials is complex because both biochemical and artificial fibers are contained in the body. Due to the effect of internal fibers, anisotropic mechanical characteristics of leathers are observed. Also, the fiber orientations are dispersed, and fiber orientation dispersion and degree of anisotropy have correlations. Regarding the manufacturing process of sports equipment made with artificial and natural leather materials, it is important to consider the anisotropic mechanical characteristics and fiber orientation dispersion to improve design performance. In this study, uniaxial tensile loading tests were conducted on three types of leather materials to investigate their anisotropic characteristics, and an anisotropic hyperelastic model for leather materials was proposed. Also, numerical simulations using the finite element method (FEM) were performed. Tensile loading tests were performed on an artificial leather and two types of natural leather. The results revealed that all materials exhibited anisotropic behaviors and different anisotropic characteristics were observed in each material. The existence of one fiber family was revealed in the artificial leather and that of two fiber families was revealed in the natural leathers. Regarding the FE simulations, the mechanical properties of the three types of leathers were reproduced by the proposed model. The mechanical characteristics of leather materials which had one fiber family and two fiber families could be reproduced. The applicability of the proposed hyperelastic model to evaluate the mechanical properties of leather materials was demonstrated.