Homogenization Analysis of Porous Polymer Considering Microscopic Structure

In this study, a homogenization analysis of porous polymer to consider the microscopic structure was conducted. This analysis allows the establishment of a design method for porous polymer for sports equipment. The mechanical characteristics of porous polymers are determined by mechanical characteristics of the polymer's matrix and microscopic structure. In this study, a porous polymer was defined as a material which has a periodical microscopic structure. Deformation of the microscopic structure was uniform, and microscopic periodicity was kept under finite deformation. The polymer matrix was assumed to have incompressible hyperelasticity, which was represented by the Mooney-Rivlin model. An original 2-dimensional simulation program was also developed. Mechanical uniaxial tensile tests using porous polymers for sports equipment were conducted. The effect of porosity on mechanical characteristics was investigated. Specimen porosities were 26%, 61%, 66%, and 76%, and pore shape was nearly spherical under microscope observation. Results revealed a reduction in stiffness with increase porosity. Also, a linear relationship between porosity and initial stiffness was revealed. The simulation model also had periodic and equally-sized pores. Porosity was reproduced by adjusting the diameter of the pores. Uniform deformation and a periodic boundary condition were applied to the unit cell. Results revealed a reduction in the simulated stiffness. Stress concentration on the microscopic structure was confirmed. The stiffness reduction can serve as a design index of porous polymer.