Impacts of defect distribution on the ignition of crystalline explosives: An insight from the overlapping effect

Many challenges remain in our understanding of the role that heterogeneities play in determining material responses, especially under extreme conditions. In this study, four defect distribution patterns were first built and shocked to quantitatively assess the effects of the spatial distribution of void defects on the hot spot formation and ignition of 1,3,5-trinitroperhydro-1,3,5-triazine crystals through reactive molecular dynamics simulations. A high correlation was found between void concentration and the hot-spot temperature, average temperature, and energy release rate of the defect distribution patterns, which is referred to as an overlapping effect. A higher dispersion degree of defects can result in a lower overlapping effect. A higher concentration of void defects leads to a higher shock-induced average system temperature, a higher increasing rate of temperature, and a higher energy release rate. Two hot spots could grow into a larger hot spot when they are closer (i.e., in a void pattern with a smaller dispersion degree), which is beneficial for the growth of chemical reactions and explosive ignition. Otherwise, they could be quenched due to their subsequent heat dissipation. For the shock-induced decomposition, a one-dimensional pattern of void defects exhibited the highest RDX decay rate and yielded reaction products the earliest compared with other patterns.