Enhancing the through-thickness thermal conductivity of carbon fiber polymer-matrix composites by nanostructuring
Lin, Jan T.
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A combined method of microstructuring and nanostructuring has been developed to improve the through-thickness thermal conductivity of carbon fiber polymer-matrix composites. The nanostructuring involved applying carbon black to the interlaminar interface. Ethylene glycol monoethyl ether was found in this study to be the most compatible vehicle for uniform carbon black dispersion. A successful formulation for nanostructuring was developed, which involved immersing the carbon polymer prepregs into the dispersion bath and allowing the vehicle to evaporate before curing. The fabrication of the composite proved efficient by using a hot press. Evaluation by electrical resistivity showed the optimum concentration for carbon black on a crossply configuration interlayer surface to be 0.8 wt. % carbon black in vehicle. The through-thickness thermal conductivities (without carbon black) for commercial carbon-epoxy composite, carbon-nylon composite and laboratory made carbon-epoxy composite were studied and were found to be around 1.0 W/m·K. The effect of ethylene glycol monoethyl ether (vehicle) on the interlaminar interface of carbon-epoxy composites was studied and was found to improve the through-thickness thermal conductivity by up to 25%. In the case of carbon black (0.8 wt. %) and vehicle, the through-thickness thermal conductivity improvement was up to 64%. The unidirectional through-thickness thermal conductivity was further improved to 1.79 W/m·K, 72% higher than composites without nanostructuring, by adding more carbon black to the interlaminar interface, namely 1.2 wt. % carbon black.