Uni-axial stress-strain response and thermal conductivity degradation of ceramic matrix composite fibre tows

A physical model, previously developed by one of the authors, has been extended to cover thermal conductivity degradation owing to the uni-axial stress-strain response of aligned groups of fibres or tows found in ceramic matrix composites. Both the stress-strain and thermal models, together with their coupling, have been shown to predict known composite behaviour qualitatively. The degradation of longitudinal thermal properties is shown to be driven by strain-controlled fibre failure; while the degradation of transverse thermal properties is because of the growth of fibre-matrix interface wake-debonded cracks, coupled with strain-driven fibre failure.