Effect of strain rate on compressive properties of foamed polyethylene film

The purpose of this study is to clarify the effect of strain rate on the compressive properties of foamed polyethylene film. A compressive test was carried out using three different testing machines to obtain the compressive properties at a strain rate of 10−4 to 103 s−1. The strain rate sensitivity of strength shows a low value in an impact test in comparison with a quasi-static test. To elucidate the mechanism of strain rate sensitivity, the deformation behavior of cell structure was observed using X-ray computed tomography before and after the compressive test. In the quasi-static test, it was observed that the cell structure was collapsed and cell wall was fractured. On the other hand, the cell collapse did not occur in the impact test. In addition, the outflow behavior of the fluid entrapped in a closed cell was visualized in the impact deformation using the Schlieren method. The entrapped fluid in the cells did not flow out in the impact deformation. It was revealed that the strain rate sensitivity of the foamed film was affected by the deformation behavior and the outflow behavior of the fluid entrapped in the cells.