Spallation of polycarbonate under plate impact loading.

We investigate spallation of polycarbonate under plate impact loading. The Hugoniot equation of state up to ∼ 1.3 GPa (corresponding to a peak particle velocity ∼ 380 m / s) is obtained, and spall strength and corresponding strain rates are determined at peak shock stresses up to ∼ 2.4 GPa (corresponding to a peak particle velocity ∼ 600 m / s). With increasing shock strength, the transition from strain-hardening to softening at shock states occurs as a result of shock heating; spall strength remains approximately constant, followed by a rapid drop upon strain softening. Release/tensile melting occurs at higher impact velocities. Three-dimensional void configurations of the postmortem samples are obtained via X-ray computerized tomography. The small voids are flat and curved for low-speed shots but become ellipsoidal for high-speed shots, and their coalescence leads to different shapes likely due to different damage mechanisms. [ABSTRACT FROM AUTHOR]