Application of the EPU Constitutive Equation to expanded Polypropylene under Dynamic Loading

A constitutive equation, which was suggested for describing the compressive deformation behaviour of the expanded polyurethane, was applied to the expanded polypropylene under dynamic loading. This equation consists of seven parameters, five of which are obtained by fitting the stress strain curve obtained from the quasi-static compression test at the lowest base strain rate. The remaining two parameters are able to be determined by fitting the curve from the compression test at different two stage strain rates. In order to check the eligibility of the equation at high strain rate, the impact test was performed and the results were compared to the analytical constitutive equation results for the expanded polypropylene with expansion ratios of 30 and 40 times, respectively.