2-Dimensional Homogenization FEM Analysis of Hyperelastic Foamed Rubber

Foamed rubbers are widely used for the shoe-soles, shin-guards, protectors and so on. The complex microstructure of foamed rubber consists of rubber matrix and pores. Therefore, foamed rubbers show good shock-absorbing properties in addition to good formability and lightweight. The mechanical characteristics of foamed rubber are determined by the mechanical characteristics of rubber matrix and its microstructure.In this study, a homogenization numerical analysis of mechanical characteristics of foamed rubber considering the rubber matrix and microstructure was shown. In order to develop the evaluation method, the microstructure of the foamed rubber was assumed to have the periodical holes, and a homogenization FEM code for formed rubber was developed based on homogenization theory with hyperelasticity. To verify the applicability of our developed code, rectangular rubber specimens with periodically holes were prepared to observe stress distributions of periodical inner structure. Incompressible hyperelasticity was applied to the rubber matrix. The material parameters of hyperelasticity for rubber matrix were identified by the biaxial tensile test results. Compression test of the rubber specimen reproducing FEM model was conducted to verify the applicability of the analysis code. The analysis result showed good agreement with the compression test result in the low strain region.