Hypervelocity-impact experiments are performed on SiO 2 glass plates to investigate its damage process. The damage propagation behavior induced by a hypervelocity impact is observed using a high-speed video camera. The postmortem observations reveal that the damage structure of the impacted plates consists mainly of crater, internal failure zone, and radial cracks. The sequence of the damage formation and propagation during a hypervelocity-impact event is revealed using the images of the

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... eed video camera. The propagation velocities of surface fracture show a nearly constant value regardless of impacting conditions. The propagation velocities of internal failure zone increase with decreasing target thickness. The formation of radial cracks is affected by the projectile kinetic energy normalized by the target thickness. The radial crack velocities increase with increasing the normalized kinetic energy and approach asymptotically to the terminal velocity.