A unified model for the thermal and electrical conductivities of highly oriented graphene–ceramic matrix composites

Ceramic matrix composites serve as crucial structural materials for hot-section components in next-generation aeroengines and aerospace propulsion systems. As functional reinforcements, graphene fillers have been introduced into ceramic matrices to form graphene–ceramic matrix composites (GCMCs), with the potential for enhanced thermal and electrical properties. In such composites, interfacial effects and graphene orientation are important influencing factors. Pressure-assisted sintering induces highly oriented graphene alignment that can be described by Gaussian distribution, leading to complex predictive formulations. Thus, this study proposes a unified theoretical model to evaluate the anisotropic thermal and electrical conductivities of GCMCs. For the orientation distribution of graphene fillers, an equivalent relation between the parameters of a Gaussian distribution and those of a uniform distribution within a finite angle range is established, enabling accurate predictions using a simplified formulation. Two categories of interfacial effects are considered, including Kapitza and contact thermal resistances for heat conduction and the tunneling effect for electrical conduction. The enhancements of thermal and electrical conductivities differ with graphene addition due to different interfacial effects, accompanied by contrasting anisotropy evolutions. Electrical anisotropy tends to stabilize after percolation, whereas thermal anisotropy evolves continuously with increasing graphene volume fraction.