Abstract
In this study, a series of hypervelocity impact (HVI) experiments for silica glass plate targets were conducted to evaluate the nucleation and propagation mechanisms of spall-like damage on backside of the plates by impacting a small projectile with various conditions. Backside damage nucleation and propagation behavior was observed from two directions (side-backside) simultaneously by means of in-situ scattered light imaging coupled with an ultra-high-speed video camera. spall-like damage nucleated discontinuously with any front side damages at an area on back surface which had certain relation with change of target thickness. Nucleated damage propagated radially from each point. when the expanded damages connected with each other in high energy conditions, circular spall appeared on back surface. These observation results were compared with estimated stress wave propagation behavior, and it was suggested that the impact induced transversal stress wave affect to the nucleation and propagation. It was suggested that this damage process was quite different from the spallation of metal or other ceramics materials.
