Simulation guided experimental interface shock viscosity measurement in an energetic material

Abstract

Experimental measurements of interface shock viscosity in hydroxyl-terminated polybutadiene (HTPB)-ammonium perchlorate (AP) material system are performed using mechanical Raman spectroscopy (MRS) combined with laser pulse shock loading. First, HTPB-AP interface level shock wave propagation is studied using the cohesive finite element method. The difference in the shock behavior of the analyzed HTPB-AP interfaces from that of the bulk AP and HTPB material is highlighted by numerical simulations of impacting a single AP particle in an HTPB-AP sample in three different ways: (1) a flyer plate is used to impact the whole HTPB-AP sample; (2) a flat impacter is used to impact the middle of AP particle embedded in HTPB matrix directly; and (3) a HTPB-AP interface is directly impacted with an impacter of radius 1 μm. Shock wave rise time at the interface is shown to differ for the three different impact modes. Based on the simulation results, a combined MRS and pulse laser-induced particle impact test is used for measuring shock viscosity at HTPB-AP interfaces. It is observed that by changing the chemical composition of the interface, shock viscosity can be altered. A modified finite element model with viscous stress based on shock viscosity values added to the stress equation is then used for the shock impact simulation of an HTPB-AP material system. A power law relation was obtained between shock wave rise time and the shock viscosity.