Optimizing the transverse thermal conductivity of 2D-SiCf/SiC composites. I. Modeling

For potential fusion energy applications, considerable fabrication efforts have been directed to obtaining transverse thermal conductivity (Keff) values in excess of 30 W/m K (unirradiated) in the 800–1000 °C temperature range for 2D-SiCf/SiC composites. To gain insight into the factors affecting Keff, at PNNL we have tested three different analytic models for predicting Keff in terms of constituent (fiber, matrix and interphase) properties. The tested models were: the Hasselman–Johnson ‘2-Cylinder’ model, which examines the effects of fiber–matrix (f/m) thermal barriers; the Markworth ‘3-Cylinder’ model, which specifically examines the effects of interphase thickness and thermal conductivity; and a newly developed anisotropic ‘3-Square’ model, which examines the potential effect of introducing a fiber coating with anisotropic properties to enhance (or diminish) f/m thermal coupling. The first two models are effective medium models, while the third model is a simple combination of parallel and series conductances. Model predictions suggest specific designs and/or development efforts directed to optimize the overall thermal transport performance of 2D-SiCf/SiC.