Sensitivity of predictions of critical energy of heterogeneous energetic materials to reaction kinetics models

Detonation of heterogeneous energetic materials (HEs) is initiated at hot spots. Reaction fronts propagate from such hot spots resulting in complete consumption of the surrounding material. The meso-structures of HEs such as plastic bonded explosives (PBXs) and pressed materials are replete with voids, defects and interfaces, which are sites of hot spot formation. To predict the response of HEs at the macro-scale, the meso-scale dynamics must be captured and the localization of energy that results from shock focusing and interfacial interactions must be quantified. Capturing such highly localized events that are crucial to performance prediction require a thorough understanding of the chemical reaction kinetics that govern the decomposition of solid energetic crystals to gaseous products. In the current work, multi-scale simulations are performed to investigate the uncertainties in the chemical kinetics parameters. Ensembles of high-resolution reactive void collapse simulations are performed considering the global Arrhenius parameters for pressed HMX materials to construct a meso-informed surrogate model in a high dimensional parameter space. Then macro-scale computations of shock-to-detonation (SDT) transition are performed using the meso-informed Ignition and Growth (MES-IG). The performance of the HE at the macro-scale is evaluated via the critical energy required for initiation in the Walker-Wasley/James space. The predicted critical energy envelopes are compared with experimental data. The results quantify the effects of uncertainties in the chemical kinetics parameters on the macro-scale sensitivity predictions, and provide a best estimate for the experimental data. The meso-informed surrogate model developed in this study will guide an expansion of reaction kinetics models to reliably predict macro-scale sensitivity for other HE species such as RDX, TATB etc.