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

The Hasselman-Johnson (H-J) model for predicting the effective transverse thermal conductivity (K-eff) 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 K-eff 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 K-eff 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 degreesC, respectively. After irradiation to saturation doses at 200 or 1000 degreesC, the respective K-eff-values are predicted to decrease to 6 or 10 W/(m-K). (C) 2002 Elsevier Science Ltd. All rights reserved.