Computational analysis of ignition in heterogeneous energetic materials

This paper focuses on the ignition of polymer-bonded explosives (PBXs) under conditions of non-shock loading. The analysis uses a recently developed ignition criterion [1] which is based on the quantification of the distributions of the sizes and temperatures of hotspots in loading events. This quantification is achieved by using a cohesive finite element method (CFEM) developed recently and the characterization by Tarver et al. [2] of the critical size-temperature threshold of hotspots required for chemical ignition of solid explosives. Calculations are performed on PBXs having monomodal grain size distributions with grain volume fractions varying between 0.72 and 0.90. The impact velocities considered vary between 100 and 200 ms^-1. Results show that the average distance between the hotspots is dependent on the grain volume fraction. As the grain volume fraction increases, the time to criticality (t_c) decreases, signifying increases in the ignition sensitivity of PBX to impact loading. The microstructure-performance relations obtained can be used to design PBXs with tailored performance characteristics and safety envelopes.