Low pressure shock response and dynamic failure of high density polyethylene (HDPE)

Abstract

Polyethylene is a widely-encountered polymer that exhibits mechanical responses tailorable to a given application based on its network and chain structures (crystallinity) and molecular weight. Several earlier reports have provided shock Hugoniot data for polyethylene over a broad range of conditions to very high shock stresses, while other reports have focused on the unusual and discontinuous low pressure Hugoniot of crystalline forms of polyethylene. Very little has been published on dynamic failure, i.e. spall, in polymers in general, let alone PE specifically. In this paper, high density polyethylene with crystallinity >40% was investigated both for the shock response using in situ electromagnetic gauges and the dynamic tensile failure using photon Doppler velocimetry (PDV). The evolution of particle velocity wave profile with wave propagation distance is presented to study the previously reported discontinuous Hugoniot at low pressures, providing evidence of a three-wave structure above a shock stress of 0.5 GPa. Above this region, the transition is overdriven, and a single shock wave is observed to shock stress greater than 10 GPa. Dynamic tensile experiments were conducted in the pressure region above where spall had been previously observed, and a shallow pullback signal with some ringing was observed.