Observing Hot Spots in a Model Plastic-Bonded Explosive with Shock Compression Microscopy*

Hot spot behavior influences the sensitivity and shock-to-detonation transition of plastic-bonded explosives (PBXs). Yet, experimental observation of hot spots has been precluded by detection techniques which can resolve the multiple time and length scales at which hot spots exist (fs-µs, nm-µm). We aim to better understand the underlying, microstructure-induced sensitivity of PBXs by, 1) conducting tabletop experiments on individual explosive crystals to elucidate hot spot dynamics and temperatures, and 2) comparing results to microstructurally informed, reactive simulations. We have developed a tabletop apparatus which employs laser-driven flyer plates to impart initiating shocks to the explosive sample. Multiple optical and spectroscopic probes are coupled to the apparatus which image explosive emission with μm spatial resolution and resolve hot spot temperatures down to several ns. The explosive samples consisted of 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane single crystals embedded in a transparent polymer which are shocked at several input pressures. Simulations were conducted using conducted using interface-resolved reactive simulations using a sharp-interface Eulerian framework.  This new methodology provides the means to evaluate the influence of microstructural energy localization and predict mesoscale behavior of PBXs.