X‐ray Phase Contrast Imaging of the Impact of Multiple HMX Particles in a Polymeric Matrix

The initiation of high explosives (HEs) under shock loading lacks a comprehensive understanding: particularly at the particle scale. One common explanation is the hot spot theory, which suggests that energy in the material resulting from the impact event is localized in a small area causing an increase in temperature that can lead to ignition. This study focuses on the response of HMX particles (a common HE) within a polymer matrix (Sylgard‐184®), a simplified example of a polymer‐bound explosive (PBX). These PBXs consist of multiple HMX particles in a single polymer‐bound sample. A light gas gun was used to load the samples at impact velocities above 400 m/s. The impact events were visualized using X‐ray phase‐contrast imaging (PCI) allowing real‐time observation of the impact event. The experiment used two different types of samples (multi‐particle and two crystals) and found evidence of cracking and debonding in both sample types. In addition, it was found that the multiple particle samples showed similar evidence of damage at lower velocities than that of single particle samples. This is an expected result as the multiple particles add additional interfaces for stress concentration and frictional heating.