Discrete shear failure planes resulting from oblique hypervelocity impacts

Abstract

A combination of laboratory and numerical experiments examines the role of shear localization in subsurface damage following very oblique (15–30°) hypervelocity impacts. Laboratory experiments reveal subsurface damage planes (“blades”) parallel to the impact trajectory for highly oblique impacts (15–30°), which are characterized by unique surface textures relative to other failure regions. Observations of growth rate and surface texture of the damage planes combined with three-dimensional CTH simulations indicate that the blades are the result of frictional processes during localized shear deformation. Laboratory experiments also reveal that impact angle and projectile failure play a role in the development of these blades: aluminum projectiles result in distinct along-trajectory blades for both 15° and 30° impacts, whereas the blades are weakly developed for Pyrex projectiles and nonexistent for planar polymethylmethacrylate projectiles. The blades form early in the cratering process and are signatures of the projectile momentum being transferred into the target. Based on the growth rate, and melting seen along the surface of these damage planes, the blades may provide an analog for the generation of pseudotachylytes during the early stages of impact crater formation.