Influence of Microballoon Additives on the Shock Initiation Behavior of HMX-Silicone Formulations

Novel manufacturing methods enable tailoring of mesoscale-level heterogeneities in solid high explosives (HEs). These heterogeneities influence the shock initiation behavior of HEs and may be used to meet desired safety and performance metrics. The inclusion of microscopic additives, such as microballoons, is of great interest in the HE community; however, the current influence of these components on shock initiation response is not well characterized. In this work, two-dimensional (2D), microstructure-explicit shock loading simulations are performed on HMX/silicone formulations with microballoons present in the silicone binder. The simulations are carried out using a multi-physics Arbitrary Lagrangian-Eulerian code (ALE3D). The influence of these additives on the rate of chemical reaction in HMX is analyzed as a function of microballoon size, material, thickness, and interior contents. The microballoons are represented by gas-filled glass and polymer beads and results are compared to their solid counterparts. We find that the inclusion of microballoons increases the sensitivity of the HE formulation and heat transfer plays a significant role in the development of hotspots in the HMX.