Coupled infrared laser-thermo-mechanical response of RDX-PCTFE energetic aggregates

Abstract

A computational approach is developed to investigate the coupled phenomena of high frequency electromagnetic (EM) wave propagation, laser heat absorption, thermal conduction, and inelastic dynamic thermo-mechanical deformation in heterogeneous energetic materials. The method is used to study hot spot formation in RDX-PCTFE aggregates subjected to high strain rate loads and infrared laser irradiation. The approach couples Maxwell's equations with a dislocation density-based crystal plasticity formulation within a nonlinear finite-element approach to predict and understand thermo-mechanical response due to the interrelated effects of dielectric heating, adiabatic heating, thermal decomposition, and heat conduction. RDX crystalline interfaces and orientations, polymer binder, inelastic strains, dislocation-density evolution, and voids significantly affected the coupled EM-thermo-mechanical response. EM and thermo-mechanical mismatches at interfaces between RDX crystals, binder, and voids resulted in localized regions with high electric field and laser heat generation rates, which subsequently led to hot spot formation. It is predicted that incident laser intensity and plastic shear strain localization are the dominant mechanisms that lead to hot spot formation.