Stress-wave propagation and damage formation associated with hypervelocity penetration into polycarbonate

Hypervelocity impact experiments have been performed on polycarbonate to observe the impact-induced damage process progressing inside polymer material. Impact experiments have been conducted by impacting a sphere made of several kinds of materials using a two-stage light-gas gun. The damage evolution and stress wave propagation associated with hypervelocity impact have been observed via shadowgraphy using an ultra-high-speed camera. Recoded images clearly demonstrate how damages form during the hypervelocity impact event. The obtained time evolution of penetration show that the behavior of stress wave propagation associated with impact vary according to the penetrating motion, and the impact velocity dependence of penetration length and shape change depending on the deformation and fracture behavior of impactor during penetrating process. From these results, it is indicated that not only the mechanical characteristics of impactor material but also the change of penetrating motion associated with the deformation and fragmentation of impactor are key factors for impact-damage formation.