Microstructural finite-element modelling of a ceramic matrix composite to predict experimental measurements of its macro thermal properties

A new experimental test rig has been used to measure the thermal diffusivity of a fibre-reinforced ceramic matrix composite material (C/C-SiC) using laser pulse heating under conditions of both one-dimensional and three-dimensional heat transfer. To predict these measurements, a microstructural geometric unit cell model of the material has been developed from optical micrographs and which incorporates fibre tows, matrix and interface materials. With the selection of a suitable finite-element mesh to model each material phase and the prescription of appropriate boundary conditions, this model has then been analysed for conditions of steady-state and transient heat conduction. In this way macro-thermal properties have been calculated from the micro-thermal properties of each phase of the composite. The micro-thermal properties deduced from the analyses for these thermal conditions are in close mutual agreement, and within the bounds of numerical error. These results are presented in this paper alongside the experimental measurements. It is concluded that with careful geometric modelling and sensible property data selection, the micro-thermal properties obtained from the unit cell model can accurately predict the experimentally measured macro-thermal properties.