Simulating Hypervelocity Impacts to Monolithic High-Density Polyethylene Plates

Abstract

Thermoplastic polymers as intermediate layers in protective structures could offer hypervelocity impact (HVI) damage resistance without compromising on weight and cost. Moreover, the ability to accurately simulate the ultra-high strain rate response of polymers would enable protective structure development and optimization. In a previous study, HVI experiments were performed using a two-stage light gas gun to probe the HVI response of high-density polyethylene (HDPE). 6.35 mm thick, monolithic, square targets were subjected to a series of normal, 2.0-6.5 km/s, 10 mm diameter aluminum sphere HVIs. The debris cloud tip velocity, perforation radius, and target mass loss were found to increase with impact velocity. High-speed images displayed apparent HVI-induced bulk melting and large-scale plastic deformation in the HDPE targets. In the current study, the HVI experiments were simulated using established material models and equations of state (EOS) in the Elastic Plastic Impact Computation (EPIC) code. Appropriate material model and EPIC code simulation parameters were calibrated to improve the correlation of HVI damage metrics (e.g., damage morphology, debris cloud geometry and velocity). The EPIC simulation results agree well with the experiments across most of the tested velocity regime and provide useful data to help infer the extreme target strain rates and temperatures induced by HVIs.