Finite-element modeling of heat transfer in carbon/carbon composites

A finite-element model has been developed to predict the thermal conductivities, parallel and transverse to the fiber axis, of unidirectional carbon/carbon composites. This versatile model incorporates fiber morphology, matrix morphology, fiber/matrix bonding, and random distribution of fibers, porosity, and cracks. The model first examines the effects of the preceding variables on the thermal conductivity at the microscopic level and then utilizes those results to determine the overall thermal conductivity. The model was able accurately to predict the average thermal conductivity of standard pitch-based carbon/carbon composites. The model was also used to study the effect of different composite architectures on the bulk thermal conductivity. The effects of fiber morphology, fiber/matrix interface, and the ratio of transverse fiber conductivity to matrix conductivity on the overall composite conductivity was examined.