Effects of large-sized granules on ignition and burning of powdery explosives under drop-weight impacts

Drop-weight impact experiments are performed on a thin layer of cyclotetramethylenete tranitramineand cyclotrimethylene trinitramine (RDX) powdery explosives, which were mixed with a few large-sized explosive or NaCl salt granules. The drop-weight impact machine is equipped with the high-speed photographic systems for observing the impact process. It showed that the mixed explosives are more sensitive than pure powdery explosives. Hard salt particles could greatly enhance the burning probability of powdery explosives because frictional heat between salt particles and target explosive powders, stress concentration, and new generated fragments of large granule jointly contribute to heat accumulation at the junction of dissimilar materials. Burning front always initiates at the interface of powdery explosive and additive granule. Adiabatic shear bands were frequently observed in the mixture of ultra-fine RDX powdery explosive with RDX large granules, which mainly resulted from the softening effect of ultra-fine powders once the temperature arises.