Micromechanical evaluation of thermal conductivities of polymer hybrid composites containing SiO ₂ microparticles and graphene nanofillers

The development of composite materials for thermal management is of great importance and interest to many industrial sectors. In this paper, the thermal conductivities of polymer hybrid composites reinforced by SiO 2 spherical microparticles and graphene nanofillers are predicted by means of a multi-phase micromechanical approach. First, thermal transport coefficients of the randomly dispersed graphene-filled polymer are predicted considering some critical microstructures including the graphene-graphene contact resistance, volume percentage, length and thickness of graphene, as well as the graphene-polymer interfacial layer. Then, the Mori-Tanaka method is employed to investigate the thermal conductivities of the hybrid composites in which SiO 2 particles play the role of reinforcement and the graphene-filled polymer material serves as a new matrix. The effects of material property and volume fraction of SiO 2 on the thermal transport coefficient of hybrid composites are studied. It is found that thermal conductivities of SiO 2 microparticle-reinforced composites increase with incorporation of graphene nanofillers in the polymer matrix. Also, the combination of a higher length and a lower thickness of graphene nanofillers can lead to a greater enhancement in thermal transport coefficients. The results indicate that a thinner interfacial layer further modifies the thermal transport, offering a route to optimize hybrid composite performance. This work provides critical insights into the design and engineering of advanced hybrid composites for thermal management applications.