Tensile damage in a symmetric [0/90]2s silicon-carbide fiber-reinforced titanium-matrix composite

The results of a detailed study of the effects of composite microstructure on the micromechanisms of tensile damage in a symmetric [0/90](2s) Ti-15Al-3Cr-3Al-3Sn (Ti-15-3)/SiC (SCS-6) composite are presented. Matrix microstructure is controlled by heat treatment, which is used to produce metastable beta or Widmanstatten alpha + beta microstructures. The sequence of damage initiation and evolution at room temperature is identified using ex situ scanning electron microscopy (SEM) during incremental monotonic loading to failure. Damage mechanisms are also studied using non-destructive acoustic emission (AE) techniques, and matrix hardening is characterized using matrix micro-hardness measurements within individual plies. Idealized and actual microstructure-based finite-element models are used to rationalize the observed tendency of damage to propagate from the outer plies to the inner plies. The paper highlights the importance of simplified micromechanical models in the development of a fundamental understanding of the effects of composite architecture on damage initiation phenomena. (C) 1998 Elsevier Science Ltd, All rights reserved.