MATRIX CRACKING IN CROSSPLY CERAMIC-MATRIX COMPOSITES UNDER QUASI-STATIC AND CYCLIC LOADING

Experimental data are presented for the development of 90-degrees ply and 0-degrees' ply cracking in two crossply silicon carbide fibre/calcium aluminosilicate matrix laminates under quasi-static loading. Under mechanical fatigue loading it is found that there is an increase in ply crack densities and a corresponding laminate stiffness reduction with cycling. Possible mechanisms to account for these observations are proposed. A model is presented which describes the stress/strain behaviour as a function of crack densities based on assumptions of frictional load transfer between fibre and matrix in the longitudinal plies and elastic bonding between the longitudinal and transverse plies.