Temporal scale-bridging of chemistry in a multiscale model: Simulating the shock-to-detonation transition of energetic materials

We demonstrate the prediction of the shock Hugoniot behavior, shock-to-detonation transition, and detonation properties of a prototypical energetic material (EM), RDX (1,3,5-trinitro-1,3,5-triazinane), using a particle-based, coarse-grain (CG) modeling approach. We perform at-scale, head-to-head comparisons with continuum simulations performed within a hierarchical multiscale framework concurrently coupling a macroscale finite-element model to two microscale CG models. Both CG dissipative particle dynamics simulations and hierarchical multiscale simulations (HMS) are conducted to simulate and compare 1D-planar shock impacts of pristine, micrometer-to-millimeter-sized samples of RDX over a range of shock conditions. At sufficiently strong shock impacts, run distances to detonation are observed, detonation velocities are measured, and numerical Pop plots are constructed to demonstrate consistency between the CG modeling and HMS approaches. Overall, the at-scale, head-to-head comparisons between the microscale coarse-grain and multiscale finite-element models demonstrate the accuracy and effectiveness of the multiscale up-scaling approach to capture chemical kinetics while maintaining thermodynamic consistency across scales. The multiscale up-scaling approach introduced in this work enables simulation of millimeter-sized samples and provides a novel pathway to achieving microstructurally informed continuum models of EM formulations.