Mechanistic Approach for Simulating Hot-Spot Formations and Detonation in Polymer-Bonded Explosives

Abstract

This paper presents a novel computational approach to characterize hot-spot formations due to impact in polymer-bonded explosives. As the shock propagates through the grain/binder interfaces, the subsequent mechanical and thermal processes lead to localized temperature spikes that can contribute to the ignition of the material and transition to detonation. Hot-spot characteristics are affected by small variations in the microstructure of the polymer-bonded explosive, and therefore require an accurate treatment of the wave propagation over sharp density gradients. For this purpose, a Lagrangian submodel, based on the microscale dynamical model, is used to track the grain/binder interface. Then, hot spots are characterized in terms of the intensity of the impact conditions. Statistical models for the hot spot’s size, temperature, and spatial distribution are generated using the microscale dynamical submodel. The approach uses a mechanistic hot-spot formation model to integrate the effects of the subresolution hot spot in a simulation at the macroscale. Two-dimensional simulations of a randomly packed polymer-bonded explosive sample show hot spots forming in the Estane® binder when using HMX crystals. This technique is then used in a simulation of the shock-to-detonation transition of a two-dimensional randomly packed polymer-bonded explosive. Owing to the inclusion of hot spots, the results show initiation and transition to detonation at relatively lower shock strengths, as seen in experiments.