Prediction of stress-strain and fracture behaviour of an 8-Harness satin weave ceramic matrix composite

A computationally economic finite-element-based approach has been developed to predict the stress-strain and fracture behaviour of an 8-Harness satin woven ceramic matrix composite with strain-induced damage. The finite element analysis utilises a solid element to model the behaviour of the homogenised orthotropic uni-directional tow and its matrix. The underpinning models of the tow and matrix, (Tang et al., 2009) capture the physics of the interactions between fibres and matrix; and, in this way, permit modelling that bridges the length scales of the fibres and full-scale components. The non-linear multi-axial stress-strain behaviour of the composite has been discretised by multi-linear elastic curves; and the latter has been used as input to a user defined subroutine, UMAT, in the commercial finite element package, ABAQUS. A partial unit cell model has been constructed of the 8-Harness satin weave composite of carbon fibres embedded in an amorphous carbon matrix, HITCO C/C. Predictions of the global stress-strain curve, which include the effects of fibre waviness, have been made for two failure modes: the first by deformation localisation, and the second by dynamic tow failure on fibre fracture, triggered by instantaneous pull-out deactivation. Comparisons have been made between the predictions and experimental data that exhibit two classes of fracture behaviour: brittle and quasi-ductile. The predicted results, both with and without tow waviness, compare well with the experimental data; however, the predictions for waviness are slightly better. The two extremes of experimental behaviour have been found to correspond with the two tow fracture criteria modelled.