Foamed plastics have been used in many engineering fields because of their superiority in low density, energy absorption, thermal insulation, and acoustic damping capacities. With foams, it is known that the microstructure of cells directly relates to macroscopic deformation behaviour. However, mechanical properties based on microstructures composed of non-uniform cells have not been fully understood. This study aims to clarify the mechanical properties grounded on microstructures of foamed plastics subjected to dynamic loading. The quasi-static and dynamic compression test was carried out using foamed plastic with anisotropy in the cell structure, then the strain rate dependence of deformation and energy absorption characteristics was investigated. It was confirmed that the local buckling of the cells was the dominant deformation mode in the plastic collapse of the test piece. It was also confirmed that cell buckling was initiated around the middle in the height after the plastic collapse, then propagated to the whole specimen in both the quasi-static and dynamic tests by using digital image correlation. The stress-strain relationships and the amount of absorbed energy showed strain rate dependence owing to the deformation mode in which the local buckling of the cells is dominant.
Rate dependence of electrical and mechanical properties of conductive polymer nanocomposites
