(268h) Failure Behavior of Polycarbonates Subjected to Ultra-High Strain Rates Impact

Understanding the failure behavior of materials subjected to extreme impact events can lead to the development of protective systems that can protect human life and critical infrastructure from those events. Here, we report the failure behavior of monolithic polycarbonate plates subjected to ultra high strain rates due to the impact of a 4 mm projectile traveling in the velocity range of 3-6 km/s achieved using a two-stage light gas gun (2SLGG). Commercial grade polycarbonates with two different molecular weights have been considered. The glass transition temperature (Tg) determined by dynamic mechanical analysis (DMA) and dielectric thermal analysis (DETA) shifts to a higher temperature with increasing strain-rate. High-speed videos taken during the impact event captures the fluid-like flow of the ejecta material in the back-face debris clouds (BFDC). This behavior is different from PMMA, another glassy polymer, where glass-like failure with finely particulated BFDCs has been observed. Although Tg increases with increasing strain rate, the adiabatic heating process during the perforation event leads to a liquid-like flow behavior. The change in failure behavior as a function of molecular weight and plate thickness will be presented.