Mode I delamination onset in carbon fibre reinforced SiC: Double cantilever beam testing and cohesive zone modelling

Delaminations are critical defects to the structural integrity of ceramic matrix composite (CMC) structures. They may be induced during processing due to differing shrinkage of fibres and matrix. The focus of this work is on the crack onset in order to determine conservative load limits for locally delaminated samples and components. Therefore, the critical energy release rate is determined for carbon fibre reinforced silicon carbide, C/C-SiC, at varying initial crack lengths. Double cantilever beam testing and a number of data reduction methods are applied on the fabric-reinforced C/C-SiC material. The resulting critical energy release rates are compared. The validation of the experimental energy release rate is done by cohesive zone modelling, using an average critical energy release rate in combination with a maximum stress criterion,and a linear softening rule. A good agreement of numerical and experimental crack onset loads was obtained for varying initial crack lengths. (C) 2017 Published by Elsevier Ltd.