High-fidelity simulations of shock initiation of an energetic crystal–binder system due to flyer impact

Abstract Mesoscale simulations of energy localization at hotspots provide closure models for multiscale frameworks of shock-to-detonation transition (SDT). Validation of such mesoscale calculations is challenging as direct comparison with experiments is constrained both by limitations of data acquisition in the experiments (e.g., of temperature fields) and modeling over-simplifications in the simulations. To address the latter problem and bring modeling closer to experiments, we advance a high-fidelity mesoscale computational framework for interface-resolved reactive calculations of shock initiation in plastic-bonded explosives (PBXs). Accurate resolution of shock and interfacial dynamics is achieved through higher-order (fifth-order WENO) schemes, and sharp-interface treatments are implemented for physically accurate material–material interactions. Recently obtained atomistics-consistent material models are used for HMX, with the grid resolution taken down to atomistic scale ( O (nm)). The crystal geometries are obtained directly from experiments via nano-CT imaging. The impacting flyer plate, energetic crystal, and binder are tracked as distinct phases, and flyer–binder impact and separation are simulated, capturing the flyer deformation and the effects of relief waves from the flyer surface. By integrating these high-fidelity modeling components, we evaluate how closely simulations can approach experimental data, identify the modeling aspects that most significantly influence mesoscale metrics of interest, and highlight areas for further improvement. We show that the treatment of boundary conditions for flyer impact plays an important role in producing physically correct shock wave and hotspot characteristics, which are not obtained by imposing phenomenological boundary conditions, which mimic impact conditions. Another key finding of this study is that the atomistics-consistent material model and temperature-dependent relation for specific heat together play a pivotal role in accurately capturing the elastoplastic response of HMX—demonstrating consistency with molecular dynamics by resolving shear dislocations under weak shock conditions and with experimental data through well-matched hotspot temperatures during strong shock initiation.