Effects of Microstructural Void Distribution Relative to Reactive Grains and Polymer Binder on the Detonation Sensitivity of a Heterogeneous Energetic Material

Fully three-dimensional (3D) microstructure-explicit and void-explicit mesoscale simulations of the shock to detonation transition (SDT) in a polymer-bonded explosive (PBX) are performed. The material consists of 75% PETN (pentaerythritol tetranitrate) grains and 25% HTPB (hydroxyl-terminated polybutadiene) polymer binder by volume. The model is 1×1×5 mm and has porosities up to 10% in the form of spherical voids that are 50 µm in diameter. An Arrhenius reactive burn model is used to capture the chemical reaction rate of the PETN grains, resolving the heterogeneous detonation behavior of the PBX. Imposed piston velocities ranging from 800-1500 m/s, result in an applied shock pressures of 3-8 GPa. The quantity of interest is the run distance to detonation (RDD) as it relates to microstructure and porosity. To quantify uncertainties in the behavior arising from the microstructure and void distribution, statistically equivalent microstructure sample sets (SEMSS) are generated, leading to probabilistic formulations for the RDD as functions of shock pressure. The calculations reveal that the location of voids significantly affect the RDD. Understanding void placement and microstructure effects can lead to better designed materials which can be tailored to have specific properties.