High-speed penetration dynamics of polycarbonate

Abstract

Ballistic impact experiments are conducted to investigate high-speed penetration of polycarbonate by steel spheres at impact velocities ranging from ∼600 to 2400 ms−1. High-speed photography is applied to capture the penetration processes, including projectile trajectories and cavity/damage evolution. Postmortem projectiles are characterized with three-dimensional laser scanning, and postmortem targets, with optical imaging and micro computed tomography. The maximum penetration depth varies nonmonotonically with impact velocity vi, and decreases with increasing vi above about 1777 ms−1. With increasing vi, the damage of polycarbonate targets increases significantly in amplitude and volume. The damage networks, consisting of cracks and voids, exhibit fractal features with similar fractal dimensions. At low vi, plate-shaped cracks are formed in the cavity, while needle-shaped cracks along with a large amount of melting-induced small voids, at high vi. Numerical simulations of impact penetration of polycarbonate reproduces well the experimental observations. Considering projectile distortion, a modified Poncelet model is derived to describe the nonmonotonic relation between the maximum penetration depth and vi.