The high strain rate response of PVC foams and end-grain balsa wood

The uniaxial compressive responses of two polymeric foams (Divinycell H100 and H250) and balsa wood (ProBalsa LD7) have been measured over a wide range of strain rates, ranging from 10−4 s−1 to 4000 s−1. These materials are widely used as cores for composite sandwich structures. The high strain rate compression tests were performed using a Split-Hopkinson Pressure Bar made from AZM magnesium alloy, with semi-conductor strain gauges used to measure the low levels of stress in the specimens. The experimental data for compressive strength as a function of strain rate are adequately approximated by power-law fits. The compressive yield strength of the H250 PVC foam and balsa wood doubles when the strain rate is increased from quasi-static rates (10−4 s−1) to rates on the order of 103 s−1. In contrast, the H100 PVC foam displays only a small elevation in uniaxial compressive strength (about 30%) for the same increase in strain rate.