SUMMARY

The design of new materials requires establishment of macroscopic measures of material performance as functions of intrinsic material microscopic heterogeneities. The heterogeneities in an energetic material (EM) significantly influence its ignition threshold. Traditionally, this process has been an empirical endeavor and there is a lack of systematic quantitative study of this effect both experimentally and computationally. This work presents an approach for quantifying the effects of microscopic heterogeneities such as intragranular and interfacial defects in EM via mesoscale simulations that explicitly account for such defects. The approach explicitly accounts for microstructure, constituent properties, and interfacial responses and captures processes responsible for the development of hotspot and damage. The specific mechanisms tracked include viscoelasticity, viscoplasticity, fracture, post-fracture contact, frictional heating, and heat conduction. Using this approach along with systematically composed complex 2D/3D statistically equivalent microstructure sample sets (SEMSS), the ignition thresholds corresponding to any given level of ignition probability and, conversely, the ignition probability corresponding to any loading condition are predicted for a polymer-bonded explosive (PBX) material containing different levels microstructural heterogeneities. Different ignition threshold relations such as James relation and Walker-Wasley relation are utilized to express the predicted thresholds and probabilistic ignition probabilities. The capability lends itself to the design of new materials and the analysis of existing materials.