Mesoscale Simulation of Electromechanically-Driven Dielectric Breakdown and Ignition Reaction of P(VDF-TrFE)/nAl Films under Impact Load*

To understand how its piezoelectric and flexoelectric properties can influence the ignition sensitivity of P(VDF-TrFE)/nAl as a composite energetic material (nanoaluminum particles embedded within polyvinylidene fluoride-co-trifluoroethylene binder), a two-step computational framework for microstructure-explicit simulations is developed. The model first captures the deformation and electric field (E-field) induced by the external impact load using a coupled mechanical-electrostatic framework. The development of sufficient E-field within the material leads to the initiations of dielectric breakdown and exothermic reaction in the microstructure, which are simultaneously tracked using a coupled thermal-electrodynamic-chemical framework. The breakdown is taken as the irreversible localized transition of the initially dielectric phase into a conductive phase. The reaction is simulated as a single-stage kinetic process involving the decomposition of the P(VDF-TrFE) binder and the exothermic fluorination of the nAl particles. The reaction rates are characterized using an Arrhenius relation. The transport of the chemical species is modeled as a diffusion and advection driven process by density gradient. The analyses systematically focus on the effects of loading and microstructural attributes (e.g., particle size, particle volume fraction, void size, and porosity level) on the overall ignition behavior with the determination of ignition threshold being of particular interest.