Numerical Modeling of Dielectric Breakdown in Solid Propellant Microstructures

Abstract

This study addresses the industrial issue of dielectric breakdown in aluminized solid propellants. Direct simulations at the microscale level are performed by considering monodisperse hard sphere systems obtained by a packing algorithm. Steady Maxwell equations are solved using a finite differences technique, and breakdown dynamics is modeled by a quasi-steady succession of local breakdowns between particles. Validations of the numerical procedure are successfully carried out on the prediction of the effective electrical conductivity of random suspensions of spheres. Computations of the breakdown field for monodisperse random dispersions accurately match some experimental data as well as an existing mixture law based on the mean nearest-neighbor distance. This mixture law is then applied to four industrial propellants, for which realistic microstructures have been generated and breakdown experimental are data available. It appears that this law is reasonably accurate to predict the breakdown strength of real solid propellants.