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Fragmentation history of glass projectiles impacting aluminum targets at 0.5 to 1.5 km/s

This report expands on a subset of low velocity (0.5 to 1.5 km/s) cratering experiments from a previous study (Bernhard and Horz, 1994) that employed spherical soda lime glass projectiles of 3.2 mm diameter at impact velocities from 1–7 km/s. This earlier study presented detailed crater morphologies as a function of impact speed and addressed the spatial distribution and progressive melting of projectile materials residing inside the craters. At velocities between 1 and 1.5 km/s a brittle deformation of projectile remnants were observed, precipitating additional experiments at V<1 km/s. The purpose of the present report is to describe these additional experiments and to summarize the deformation of glass impactors at 0.5 to 1.5 km/s. Two dramatically different fragmentation regimes seem evident, one a large, relatively unfractured, substantially coherent core of glass, surrounded by the second regime, an intensely fractured annulus of fine-grained material. The annulus material displays substantial struct...