Interface Defeat, Dwell and Penetration of Long Rods on Borosilicate Glass Targets

We have been investigating the impact response of transparent materials during the last several years. We have conducted long-rod impact experiments into a borosilicate glass and measured penetration and rod consumption velocities as a function of impact velocity. We also measured the failure front velocity. At sufficiently low impact velocities, the glass target resists penetration, and there is dwell. In particular, if a copper buffer is placed over the glass to eliminate the impact shock, complete interface defeat can be observed for Bernoulli stresses of 7.3 GPa. In a few cases, dwell was observed at higher Bernoulli stresses, but then the rod began to penetrate the glass, at which point the Bernoulli stress dropped to $\sim $1 GPa. The paper will describe the experimental techniques and data, and summarize results and conclusions.