Analysis of transverse thermal conductivity for mesophase pitch-based carbon fibers and the through-thickness heat conduction of their composites.

A quantitative analysis method for the transverse thermal conductivity (TC) of carbon fiber is developed, which consists of three steps including TC and morphology characterization of unidirectional composite laminate, fiber contour extraction, and finite element inverse analysis. Two different pitch-based carbon fibers with folded-radial and onion-skin microstructure are characterized, and the influences of fiber volume fraction and microstructure on the heat conduction of their composites are investigated. The equivalent transverse TCs of TC-HC-800 and PCF-1 carbon fibers are measured to be 9.27 and 2.87 W m K, respectively. The through-thickness TC of unidirectional composite exhibits rapid growth with the increase in fiber volume fraction. The finite element analysis reveals that more continuous heat conduction paths are formed with the increase in fiber volume fraction. Benefited from the bigger graphitization degree, larger cross-sectional area, and bigger aspect ratio, TC-HC-800 unidirectional composite shows higher through-thickness TC than PCF-1 composite at the same fiber volume fraction.