Stress Wave and Damage Propagation in Transparent Materials Subjected to Hypervelocity Impact

Hypervelocity impact experiments have been conducted on transparent materials, SiO2 glass and polycarbonate, to observe directly the impact-induced damage process progressing inside materials. Stress wave propagation and damage evolution associated with hypervelocity impact are visualized by employing the Edge-on Impact technique coupled with an ultra-high-speed video camera. Recorded images clearly show how stress wave propagate and interact each other, and how damages form and propagate during hypervelocity-impact event. In the impacted SiO2 glass, the damages on the ballistic direction are formed associated with the propagation of a shear wave. And, the interaction of the shear wave with the longitudinal wave reflected from free surface initiates the drastic nucleation of damage points. In the impacted polycarbonate, in addition to penetration damage and spall fracture, the delamination-like fracture is initiated by the interaction of the reflected rarefaction waves from both side free surfaces. However, such delamination fracture does not extended inside the plastic deformed region induced by the penetration of the impacted projectile.