Quasistatic and high strain rate uniaxial compressive response of polymeric structural foams

The behavior of a family of polymeric structural foams with various initial bulk densities (porosity levels) was experimentally investigated under quasistatic and high strain rate loading conditions. The high strain rate loading for the low-density image foams was implemented using a polymer split Hopkinson pressure bar (SHPB) and for the high-density image foams using a magnesium SHPB. It was found that the Youngʹs modulus, the yield strength, the maximum stress and the strain to failure increased with increasing initial foam density under quasistatic loading. The fracture modes were also found to be considerably different for these foams. The low-density foams fractured in a brittle manner, especially under dynamic loads, where as, the high-density foams exhibited shear-dominated failure at all strain rates. Under dynamic loading, the failure strength increased with strain rate but the strain to failure decreased. Based on the quasistatic and dynamic test results, the strain rate sensitivity of failure strength was determined and it was found that this rate sensitivity parameter increases with increasing foam density.