Microstructural Effect on Performance of Granular Explosives Under Shock Loading

Christopher Miller, Georgia Institute of Technology

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The detonation process of solid, energetic materials under shock loading is the result of areas of localized microstructural heating, known as hotspots. These hotspots initiate the phase transition and resulting chemical reactions responsible for detonation. Accounting for the microstructural heterogeneity, the thermomechanical response of energetic materials is computationally analyzed under dynamic loading with a wide range of loading intensities (400-1200 m/s). The framework uses a cohesive finite element method (CFEM) to capture plastic deformation, microcracks and frictional heating of computationally generated, statistically similar sample microstructures. The study focuses on the change in the microstructural ignition behavior when aluminum particles are added to a polymer-bonded explosive (PBX), which consists of HMX grains with an Estane binder. The heating in the microstructure is quantified in terms of overall energy dissipation as well as hotspot clustering and density. The overall ignition probability is determined from testing multiple samples under identical loading conditions and a 50 percent sensitivity threshold (Hugh James Curve) is developed in terms of shock power flux and the total energy fluence. This work is successfully able to predict general sensitivity thresholds seen in experiments without the need for fitting parameters. Microstructure-performance relations obtained from this analysis can be used to design explosives with tailored attributes and safety envelopes.

Abstract Author(s): C. Miller, S. Kim, Y. Horie, M. Zhou