Stress wave propagation and fracture formation in cyclotetramethylene tetranitramine (HMX)-Estane polymer bonded explosive under impact loading: A mesoscale numerical simulation

The stress wave propagation and fracture formation in HMX-Estane polymer-bonded explosive under an impact loading were studied using material point method mesoscale simulation. The stress wave propagation, temperature localizations, and material fracture behaviors were analyzed for various impact velocities, porosities, and binder volume fractions. The peak value of local longitudinal stress, due to stress wave propagation and reflection upon impact loading, was found to be higher for a larger impact velocity but lower for a greater porosity or a binder volume fraction. A spall fracture was observed in the strong tensile zones formed by the reflected wave. Greater damage was observed for either a higher impact velocity or a larger porosity. The plastic dissipation, frictional dissipation, and viscoelastic dissipation were all found to be a lead for hotspots. This study provides mesoscale explanations for stress wave propagation, the fracture mechanism, and the formation of hotspots in energetic materials.