Oblique hypervelocity impacts into graphite

Investigations have been conducted into the morphology of craters formed by impacts of aluminium and HDPE projectiles at oblique angles to graphite target plates. The experiments were conducted with a two-stage gas gun capable of launching projectiles of differing density and strength to speeds of about 6 kms−1 at right angles into target plates. It was found that, as the impact angle is decreased from the normal, the crater dimensions scaled as the normal component of the impact velocity as predicted by the ‘2/3 power law’ until a critical normal velocity was reached below which the conditions for a hypervelocity impact no longer apply. In this regime, new scaling laws were derived for the crater dimensions. It was also possible to identify a fragmentation angle below which the projectile remains intact as it ricochets across the target surface.