Effect of shrinkage constraint on damage of C/SiC composites during thermal cycles in oxidising atmosphere

Thermal cycling response of a three-dimensional C/SiC composite subjected to a unidirectional shrinkage constraint in wet oxygen was investigated. Constraint stress generated on both ends of the composite specimens during thermal cycles is shown to decrease upon heating and increase with cooling. Nevertheless, the peaks of the constraint stress gradually reduced from the initial 41 MPa to the final constant value of 9·8 MPa after 20 cycles. Residual mechanical properties and microstructure characterisation suggest that the cycled composites suffer a little mechanical degradation and the shrinkage constraint is of advantage to oxidation resistance of the materials during thermal cycles.