The transverse thermal conductivity of 2D-SiCf/SiC composites

The Hasselman–Johnson (H–J) model for predicting the effective transverse thermal conductivity (Keff) of a 2D-SiCf/SiC composite with a fiber-matrix thermal barrier was assessed experimentally and by comparison to numerical FEM predictions. Agreement within 5% was predicted for composites with simple unidirectional or cross-ply architectures with fiber volume fractions of 0.5 or less and with fiber-to-matrix conductivity ratios less than 10. For a woven 2D-SiCf/SiC composite, inhomogeneous fiber packing and numerous direct fiber–fiber contacts would introduce deviations from model predictions. However, the analytic model should be very appropriate to examine the degradation in Keff in 2D-woven composites due to neutron irradiation or due to other mechanical or environmental treatments. To test this possibility, expected effects of irradiation on Keff were predicted by the H–J model for a hypothetical 2D-SiCf/SiC composite made with a high conductivity fiber and a CVI-SiC matrix. Before irradiation, predicted Keff for this composite would range from 34 down to 26 W/(m K) at 200 and 1000 °C, respectively. After irradiation to saturation doses at 200 or 1000 °C, the respective Keff-values are predicted to decrease to 6 or 10 W/(m–K).