Effect of Impact Velocity on Dynamic Response of Polymeric Foams

The deformation characteristics of polymeric foams, when subjected to high-speed impacts are highly dependent on the impact velocity. At low impact velocities, the deformation is homogeneous. In contrast, at high impact velocities, the deformation is highly localized with the occurrence of progressive cell crushing initiated from the impact end. This leads to a “shock wave” like propagation of the deformation. In this study, the dynamic deformation behavior of a low-density rigid polyurethane foam material is investigated through high-speed impact experiments. Cylindrical polycarbonate projectiles are fired on the foam specimens at velocities ranging from 40 m/s to 120 m/s using a gas gun setup. The images of the deforming specimen are captured with a high-speed camera and processed using digital image correlation to obtain full-field deformation. It is shown through experiments that the deformation behavior at high impact velocities is significantly different from the response at low impact velocities. It is found that the strain behind the shock front significantly increases with the impact velocity.