Inter-Carbon Nanotube Contact and Thermal Resistances in Heat Transport of Three-Phase Composites

Single-walled carbon nanotubes (SWNTs) tend to aggregate into bundles due to van der Waals forces during the fabrication of the composite. A computational model using an off-lattice Monte Carlo method is developed to systematically investigate the effects of SWNT bundles, the number of SWNTs per bundle and the thermal boundary resistance (TBR) at the SWNT–SWNT interfaces on the effective thermal conductivity ( K eff ) of three-phase composites. It is found that the aggregation of the SWNTs in bundles can reduce significantly the K eff of the composites with SWNTs oriented parallel or randomly to the heat flux direction, but it enhances slightly the K eff of those with SWNTs perpendicular to the heat flux direction. The K eff of the composites also decreases when more individual SWNTs aggregate in each bundle and with larger SWNT–SWNT TBR values. The thermal transport mechanism within the composites is dominated by a critical SWNT–SWNT TBR of 0.155 × 10 –8 m 2 K/W.