Effective conductivity of composite materials made of randomly packed densified core-shell particles

Abstract

Three-dimensional microstructures of sintered core-shell spheres with various shell thicknesses and degrees of densification were numerically constructed using an available drop-and-roll algorithm with our newly developed core-shell generation as the post-processing step. An open-source software program was then used to obtain each microstructure's effective conductivity in terms of the core-shell features. The results obtained for the core-shell configuration were compared with existing models and available theoretical bounds, which showed underprediction at core-shell volume fractions φ=0.6–0.75 and overprediction when the core-shell volume fraction was larger than 0.85. Additionally, the conductive ring and straight line patterns associated with maximum intensity projection were clearly observed from axial and lateral views of the heat flux calculation, respectively. Both observed patterns were completely different than those traditionally made by solid grains, revealing inhomogeneity in the presence of core-shell structures. Such findings are expected to improve the understanding and methods used to design porous media with core-shell structures to serve as good heat exchangers or thermal insulators with high efficiency.