Detection of cracks in ceramic matrix composites based on surface temperature

Ceramic matrix composites are processed at high temperatures and experience significant residual thermal stresses upon cooling to room temperature. Th ese stresses often result in matrix cracking prior to the application of ex ternal loads. Matrix cracks may also appear as a result of thermomechanical loading. It is important to detect these matrix cracks using a nondestruct ive technique. The method proposed in this paper is based on measurements o f the surface temperature of a ceramic matrix material subjected to cyclic stresses. The elevated surface temperature is due to friction between the f ibers and the matrix that occurs in the presence of bridging matrix cracks. The solution presents a relationship between surface temperature and matri x crack spacing that can be used to identify the extent of the damage. (C) 1999 Elsevier Science Ltd. All rights reserved.