Shock-induced chemical decomposition and overdriven detonation in hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) single crystals

Abstract

Understanding the differences in the shock compression and detonation response of insensitive high explosives (IHEs) and conventional HEs (CHEs) is a long-standing need in HE science and technology. Having previously examined 1,1-diamino-2,2-dinitroethene (FOX-7) IHE single crystals [Winey et al., J. Appl. Phys. 130, 015902 (2021)], the shock and detonation response of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)—a widely used CHE—was determined using wave profile measurements in ∼250 μm thick single crystals shock compressed to 63 GPa. In marked contrast to FOX-7, RDX single crystals shocked along the [100] and [111] orientations showed wave profile features consistent with chemical decomposition onset at 15 GPa. These features were more pronounced for [100] RDX, suggesting a higher decomposition rate compared to [111] RDX. At 51 GPa and above, flat-topped single waves were observed for both orientations, showing the classic Chapman–Jouget (C–J) detonation response in which the decomposition is completed within the detonation front. The Hugoniot states and sound speeds determined for the detonation products were similar for both [100] and [111] orientations, showing that the overdriven detonation response for RDX does not depend on crystal orientation. The C–J pressure for RDX single crystals (35 GPa)—determined experimentally—is comparable to that of FOX-7. However, compared to FOX-7, chemical decomposition onset for RDX occurs at much lower pressures and the overdriven C–J detonation response occurs at higher pressures. The present findings constitute the first experimental comparison of the shock and detonation response of conventional and insensitive HE single crystals over a broad pressure range below and above the C–J pressure.