Effective thermal conductivity of 3D-printed continuous wire polymer composites

3D printing can be used to improve the geometric design of heat transfer structures by allowing the fabrication of more complex shapes which can enhance convective heat transfer; however, this can come at the expense of having a lower solid-phase thermal conductivity, especially when polymers are used. Improving the thermal conductivity of 3D-printed components has been the focus of many studies because of the potential to leverage additive manufacturing (AM) for thermal applications, such as heat exchangers. This study describes a fabrication process whereby 3D-printed polymer composites consisting of continuous metal wires and with enhanced effective thermal conductivity are fabricated using a modified fused filament fabrication (FFF) 3D printer. The wires were coextruded with the molten polymer through a modified hot end and nozzle assembly. The printed components have higher thermal conductivity than the base polymer because the wires create high thermal conductivity pathways in the printed rasters. Samples with different wire volume fractions, printing directions, and matrix materials were printed to investigate the effect of these parameters on the thermal conductivity of the printed composites. The thermal conductivity of the printed samples was evaluated experimentally using a steady-state measuring setup and analytically modeled using network thermal resistance models. The results show that 3D-printed continuous wire polymer composites can have a thermal conductivity as high as 9.4 W/mK using a volume fraction of 2.7% of continuous copper wires compared with 0.22 W/mK for the base polymer. Model results further demonstrate that usage of a higher volume fraction of conductive wires or other continuous conductive filler can further improve the thermal conductivity of these 3D-printed composites.