Prediction of Effective Thermal Conductivities of Four-Directional Carbon/Carbon Composites by Unit Cells with Different Sizes

Two-unit cells developed to predict the effective thermal conductivities of four-directional carbon/carbon composites with finite element method are proposed in this paper. The smaller-size unit cell is formulated from larger-size by two 180° rotational transformations. temperature boundary conditions corresponding two-unit derived, and validity verified heat flux distributions at specific positions cell. carbon fiber bundles rods measured firstly. Then, combined properties matrix, numerically predicted. results transverse direction predicted both higher than experimental values, which 5.8 6.2% 7.3 8.2%, respectively. In longitudinal direction, calculated 6.8% results, addition, different diameters set clarify influence on composites.