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 diffusivit y of a fibre-reinforced ceramic matrix composite material (C/C-SiC) using l aser pulse heating under conditions of both one-dimensional and three-dimen sional heat transfer. To predict these measurements, a microstructural geom etric unit cell model of the material has been developed from optical micro graphs and which incorporates fibre tows, matrix and interface materials. W ith the selection of a suitable finite-element mesh to model each material phase and the prescription of appropriate boundary conditions, this model h as then been analysed for conditions of steady-stare and transient heat con duction. In this way macrothermal 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 cl ose mutual agreement, and within the bounds of numerical error. These resul ts are presented in this paper alongside the experimental measurements. It is concluded that with careful geometric modelling and sensible property da ta selection, the microthermal properties obtained from the unit cell model can accurately predict the experimentally measured macro-thermal propertie s.