A numerical investigation on the heat conduction in high filler loading particulate composites

Particle-filled composite materials have been widely used as thermal interface materials (TIMs) to reduce the thermal contact resistance. For industrial applications, the particle-filled composite usually has high volume fraction (>50%). However, most of the research on the thermal properties of particle-filled composites has been focusing on low volume fraction composites. In this work, the finite element method (FEM) is adopted to investigate the particle-filled composites with high filler loading. We consider the close-packed simple cubic (SC), face-centered cubic (FCC), and a dual diameter (DD) model with even a higher volume fraction than the FCC. It is found that with a high volume fraction, small increase in volume fraction can lead to a strong enhancement in the overall thermal conductivity. With a certain filler loading and thermal conductivity of the matrix, the effective thermal conductivity first dramatically increases with the thermal conductivity of the filler and then saturates. We show that the effective medium theory based models cannot properly predict the effective thermal conductivity for the close-packed structures. The percolation theory based on the resistance network agrees surprisingly well with our simulation results. Through a careful investigation of the effect of proximity between adjacent particles, it is found that good contact between particles is crucial to the enhancement of the overall thermal conductivity. We also considered the interface thermal resistance between fillers and matrix and compared the simulation results with analytical models. Our analysis provides a better understanding on the heat transfer in the high volume fraction composite materials and is important for the fabrication of high thermal conductivity TIMs. (C) 2016 Elsevier Ltd. All rights reserved.