On fiber debonding and matrix cracking in fiber-reinforced ceramics

The relationships between debonding in the wake of a crack and the critical stresses for propagating a fiber-bridged matrix crack in fiber-reinforced ceramics have been studied. By adopting a shear-lag model which includes the matrix shear deformation in the bonded region and friction in the debonded region, the relationship between the fiber-closure traction and the debonded length is obtained by treating the interfacial debonding as a particular crack propagation problem along the interface. By using an energy-balance approach, the formulation of the critical stress for propagating a fiber-bridged matrix crack can then be derived. The conditions for attaining no-debonding and debonding during matrix cracking are discussed in terms of the two interfacial properties of debonding toughness and interfacial shear stress. The theoretical results are compared with experimental data of SiC/borosilicate, SiC/LAS and C/borosilicate ceramic composites. (C) 2001 Elsevier Science Ltd. All rights reserved.