Microstructure models are developed to computationally analyze the interactions between the constituents in heterogeneous materials and electromagnetic pulses (EMP). The models are used to explicitly simulate the material breakdown process by tracking the transition of dielectric constituents from non-conductive to conductive states. The focus is on the electric fields induced in the materials and the conditions for dielectric breakdown (defined as the onset of avalanche) caused by an artificially induced EMP excitation. The materials analyzed contain different combinations of dielectric and conductive constituents, a material made of cellulose-based KRAFT paper and mineral oil, PEEK 450G, and a gasket material (Parker Chomerics 1287). It is found that the electric field levels in the materials and the breakdown behavior are significantly affected by microstructure heterogeneities. The breakdown strengths of these materials depend on the microstructures, the dielectric constants, breakdown strengths, and the post-breakdown conductivity of the constituents.
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