In the present article, highly conductive vinyl ester resin/compressed expanded graphite sheet-based composites were investigated. The composites were prepared by vacuum impregnation with resin solution in compressed expanded graphite sheets of various densities. The microstructures of the composites were systemically characterized by X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry. The composites were found to be still the basic constituent unit (i.e., carbon-crystal layer) of the compressed expanded graphite sheets after resin impregnation, although the pore diameter distribution of the composites changed. The effects of resin content on the electrical conductivity of the composites were also investigated. The effective media theory and a simple generalized effective media equation were employed to predict the electrical conductivity of the composites. The experimental results of electrical conductivities (in- and through-plane directions) and the microstructure of the composites were highly consistent with simulated data in the model.
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