Onset of matrix cracking in angle-ply ceramic matrix composites

Abstract

The problem of initial damage in angle-ply [− θ m /0 n / θ m ] and [− θ/ θ] ceramic matrix composites subjected to axial tension is considered in this paper. The damage is in the form of matrix cracks that may appear in either inclined (− θ and θ lamination angle) or longitudinal layers. As follows from the analysis, if the lamination angle of the inclined layers is small, the initial failure occurs in the 0-layers of [− θ m /0 n / θ m ] composites or in [− θ/ θ] composites in the form of bridging cracks. However, if the inclined layers form a larger angle with the load direction, they fail due to tunneling cracks. It is shown that the boundary between two different modes of failure in a representative SiC/CAS composite corresponds to a lamination angle equal to 35° in the case of [− θ m /0 n / θ m ] composites. In the case of [− θ/ θ] laminates, the boundary value of the lamination angle is equal to 45°, i.e. bridging cracks form if θ<45° and tunneling cracks appear if θ>45°.