Theoretical study on thermal conductivity of epoxy composites doped with boron nitride with multiple dimensions

Abstract

Epoxy is widely used in electrical equipment owing to its exceptional physical, chemical, and electrical insulation properties. However, its low conductivity limits its applications. The incorporation of fillers with high thermal conductivities into epoxy matrices is one of the most effective and common methods for enhancing the thermal conductivities of epoxy composites. In this study, Digimat software was used to construct the models, and a numerical simulation based on representative volume elements (RVEs) was employed to investigate the relationship between the thermal conductivity and microstructure of the epoxy composites. The epoxy composites exhibited different thermal conductivities in various directions owing to the pronounced anisotropy of the boron nitride (BN) fibers. In composites filled with both spherical boron nitride (S-BN) and BN fibers, BN fibers play a dominant role in enhancing the effective thermal conductivity (ETC). However, at the same filling fraction, the composites achieved their maximum ETC when the S-BN-to-BN fiber ratio was 2:8. Furthermore, the ETC increased linearly with the filling fraction of the filler. When the volume fraction of the fillers was kept constant, the smaller S-BN particles increased the ETC of the composites. Similarly, when the number of fillers and volume fraction were kept constant, an increased aspect ratio of the BN fibers resulted in a higher ETC of the composites. An investigation of the electrothermal coupling between pure epoxy resin and epoxy-resin composite materials revealed that the stable temperature of the composites was considerably lower than that of pure epoxy. The heat transfer to the bottom of the composites was faster, which indicated a substantial improvement in the ETC.