Heat Pipe Embedded Carbon Fiber Reinforced Polymer Composite Enclosures for Avionics Thermal Management

Abstract

Carbon fiber reinforced polymer (CFRP) composite material is an attractive structural material in applications where mass is critical. The carbon fiber matrix provides strength comparable to steel with only 25% of the density. The CFRP sheet can often also be made thinner than metal with similar mechanical properties, further increasing the mass savings. However, thermal challenges have arisen with the increased use of composites. In the area of electronics enclosures, traditional metal structures conduct and spread heat over large surfaces, but composites act as insulation. Heat generated by components causes internal temperatures to rise and has detrimental impact on the performance and reliability of the electronics. A method is proposed and tested that utilizes constant conductance heat pipes (CCHPs) that penetrate through the CFRP walls. The CCHPs are capable of transporting significant heat energy through a limited crosssection with a minimal temperature penalty. CCHPs are passive, two-phase, thermal transport devices which have extremely high effective thermal conductivities on the order of thousands of W/m-K. The heat pipes serve as thermal vias, providing a high conductivity path for heat energy to pass from within the enclosure to outside the enclosure with minimal impact on the structural integrity of the wall. The CFRP is fabricated without any change to the process or tooling and the pipes are embedded in a post-formation operation. A lightweight CFRP enclosure for a PC/104 module is developed, fabricated and thermally tested with actual PC/104 electronics.