Energy localization in HMX-Estane polymer-bonded explosives during impact loading

We report the results of a mechanistic study of energy localization in a HMX (High Melting point eXplosive octahydro-1,3,5,7-tetranitro-1,2,3,5-tetrazocine)/Estane PBX system during dynamic loading. The focus is on the thermal-mechanical response over the strain rate range of 10(4) - 10(5) s(-1) under different confinement conditions. A recently developed cohesive finite element method is used to track and analyze the contributions to heating from different constituents, interfaces, deformation and fracture mechanisms, and internal friction. In particular, energy dissipations due to viscoelastic deformation, grain fracture, interfacial debonding, and friction along crack faces are quantified as functions of time and overall deformation. The materials analyzed have HMX volume fractions between 0.69 and 0.82. Calculations show that variation in strain rate can significantly affect the spatial distribution but not the overall number of hot spots. Higher confining stresses lead to more intense heating in the binder and more uniform distribution of hot spots. The evolution of hot spots is quantified as a function of loading condition, deformation and microstructural attributes. The microstructure-response relations obtained can be used to assess the initiation sensitivity of energetic composites. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3688350]