High fidelity mesoscale simulations of shock initiation through flyer impact on HMX crystal – binder aggregates*

Multiscale frameworks for shock-to-detonation transition modeling of HE materials leverage mesoscale simulations of the shock initiation phenomena for the required closure models for energy localization. Validation of such models is challenging however, as direct comparison with experiments is often limited by modeling over-simplifications. We present a mesoscale computational framework that can perform interface-resolved reactive calculations of flyer-impact induced initiation of a plastic-bonded explosive (PBX) sample, with simulation conditions closely adhering to physical experiments. The flyer, the crystal, and the binder are tracked as distinct phases; the HMX crystals are obtained from nano-CT scans. Simulating the flyer impact realistically represents the effects of the reflected relief wave. The continuum calculations are performed in a Eulerian framework, with the interfaces tracked as sharp entities. Accurate resolution of shock and interfacial dynamics is achieved through higher-order schemes and local mesh refinement, and techniques are implemented to emulate physically accurate material-material interactions. The most up-to-date material models are used for HMX, with all model forms and parameters obtained from atomistic calculations. With the above high-fidelity modeling components, we obtain new insights into hotspot growth mechanisms in HMX-binder systems for low and high strain rates.