Shock and release of polycarbonate under one-dimensional strain

The behaviour of the thermoplastic polycarbonate has been investigated using manganin stress gauges in both longitudinal and lateral orientations. These have been used to determine the shock stress, shock velocity, particle velocity, release velocity and shear strength. The relationship between shock velocity and particle velocity has been shown to be linear, with the value of c0 (the zero particle velocity intercept of shock velocity) equating to the measured bulk sound speed. This behaviour is more commonly observed in metals. Shear strength has been observed to increase behind the shock front, a feature observed in other polymers such as PMMA or PEEK. It also increases with stress amplitude, although the projected intercept with the calculated elastic response indicates that the Hugoniot elastic limit (HEL) is lower than in other polymers, for example PMMA (ca. 0.75GPa) or PEEK (ca. 1.0GPa). This further suggests that the yield strength of polycarbonate does not obey a Mohr-Coloumb criterion, and hence is not as strongly pressure dependent as other polymers.