Microwave Excitation of Crystalline Energetic Composites

Hotspots produced by microwaves radiating into an energetic composite of RDX crystals and an estane binder are examined using transient electromagnetic (EM) and coupled EM-thermal analyses. Hotspots, localized regions where energetic activity is likely to initiate, manifest as regions of peak electric field or high temperature. Stress caused by these high fields and temperatures may result in molecular breakdown, creating a chain reaction leading to the release of chemical energy via deflagration (burning and melting) in the absence of a mechanical shock wave. High peak electric fields up to three times higher than the incident field result from subwavelength scattering and occur near crystalline surfaces while peak temperatures occur in the binder, with both generally coinciding at the binder-RDX interface. Abstractions enable materials to be modeled with crystals having an average characteristic dimension of 100 μm. With an incident field of 1 MV/m the peak electric field in the composite was 2.9 MV/m and peak temperature increased by 75 K in the binder and 65 K in the RDX after 3.7 ms. The RDX fill factor of the composite was 37%, typical of an improvised explosive.