Two-Scale Prediction of Effective Thermal Conductivity of 3D Braided C/C Composites Considering Void Defects by Asymptotic Homogenization Method

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

“…The resin matrix is generally considered to be isotropic in thermal conductivities. However, as for pitch-derived matrix, the thermal conductivity in longitudinal direction is higher than the transverse direction [27,41].…”

“…The carbon fiber bundles are made by carbon fiber and pitch. The fiber volume fractions of carbon fiber rods and carbon fiber bundles are 80% and 57%, respectively [27]. The matrix pocket is regard as disordered graphite, because of the high temperature graphitization treatment.…”

“…The matrix pocket is regard as disordered graphite, because of the high temperature graphitization treatment. The thermal conductivities of all ingredients that construct 4D C/C composites are shown in Table 1, and the properties are adopted from the literature [27,42].…”

“…The carbon fiber rods are in axial direction, and the carbon fiber bundles are arranged around the carbon fiber rods in a radial plane with an angle of 0 • , 120 • , and 240 • . Then, the preform is impregnated and carbonized to construct the 4D C/C composites [27]. The prediction of the effective thermal conductivities of 4D C/C composites can be carried out on the unit cells at meso-scale, similar to other composites with periodic structure [28,29].…”

“…Gou [15] deduced the boundary conditions for quarter-size unit cell and 16th-size unit cell of 3D braided composites. For 4D C/C composites, larger-size unit cells (UC1) are usually constructed by using translational symmetry [27,36,37]. The construction of a smaller-size unit cell (UC2) for 4D C/C composites has not been discussed in the literature so far, and the applicable boundary conditions have not been derived.…”