Characterization of explosives is necessary to safely transport, store and design novel next-generation explosives. While computation models are being developed, empirical data is still required for accurate assessments, however most of the tests currently utilized are older, focusing on simple “go” or “no go” threshold screening. . Current methods for low velocity impacts (sub shock insults) testing include the US drop hammer (ERL-type test). Drop-weight impact sensitivity measurements are one of the first standardized tests performed for energetics and while multiple labs have used the impact sensitivity test as an initial screening tool for explosive sensitivity for the past 60 years, variability exists due to the use of different instruments, different methods to determine initiation, and scatter associated with less sensitive explosives. This test was originally designed for simple safety analysis and does not provide much information on the complex mechanisms that can occur to the explosive during its testing. In order to better understand the phenomena occurring under sub shock impacts studies have been conducted with an improved pneumatically powered drop-weight impact apparatus with advanced diagnostics, which we refer to as the crush gun. Using this instrument we can mimic conditions similar to the drop hammer test but with increased projectile speeds and high-speed and infrared cameras. Herein we investigate the impact sensitivity of DAAF (3,3’-Diamino-4,4’-azoxyfurazan) and HMX (1,3,5,7-Tetranitro-1,3,5,7 tetrazoctane) along with a more detailed investigation of ignition sites using a novel “crush gun” apparatus. Using this crush gun assembly, the initiation of ignition sites in HMX and DAAF have been analyzed with respect to the effects of particle size and presence of a source of grit. The formation of ignition sites was observed in both explosives, however only HMX showed ignition sites which propagated to a deflagration at lower firing speeds.
2022-04-06 08:00:00
