Spallation of polycarbonate on nanosecond timescales.

Polycarbonate is commonly used in extreme environments, particularly in applications involving high-velocity impact. A critical failure mode in high-velocity impact is that of spallation, where intersecting release waves result in the dynamic fracture of the material under high-rate tension. Despite the ubiquity of polycarbonate, major gaps exist in our understanding of its behavior at high rates over very short timescales. Here we investigate the spallation of polycarbonate on nanosecond timescales at strain rates of ∼10^{6}s^{-1} through a data set of 117 spall experiments. The size and fidelity of our dataset allow us to calculate fundamental uncertainties associated with the spallation of polycarbonate. Compared to lower rate experiments, we observe higher spall strengths, a higher spall initiation threshold, and a more gradual decrease in spall strength with increasing prior shock stress. This paper provides a strong basis for future computational model development and brings up questions on the underlying mechanisms that control spallation in polymers at extreme strain rates.