Fatigue Damage in Cross-Ply Titanium Metal Matrix Composites Containing Center Holes

The development of fatigue damage in four [0/90]_s SCS-6/Ti-15-3 laminates containing center holes was investigated. A methodology to predict damage initiation based on an effective strain parameter was used to determine the stress levels and the number of cycles required for matrix crack initiation. Damage progression was monitored at various stages of fatigue loading. In general, a saturated state of damage consisting of matrix cracks and fiber-matrix debonding was obtained which reduced the composite modulus. Matrix cracks were bridged by the 0° fibers. The fatigue limit (stress causing catastrophic fracture of the laminates) was also determined. The static and post-fatigue residual strengths were accurately predicted using a three dimensional elastic-plastic finite element analysis. The matrix damage that occurred during fatigue loading significantly reduced the notched strength.