Fatigue Cracking in Fiber-Reinforced Metal Matrix Composites Under Mechanical and Thermal Loads

This article reviews micromechanical models developed for fatigue cracking in fiber-reinforced metal matrix composites under mechanical and thermal loads. Emphasis is placed on the formulae and design charts that can quantify the fatigue crack growth and fiber fracture. The composite is taken to be linear elastic, with unidirectional aligned fibers. Interfacial debonding is assumed to occur readily, allowing fibers to slide relative to the matrix resisted by a uniform shear stress. The fibers therefore bridge any matrix crack that develops. The crack bridging traction law includes the effect of thermal expansion mismatch between the fiber and the matrix and a temperature dependence of the frictional shear stress. Predictions are made of the crack tip stress intensities, matrix fatigue crack growth, and maximum fiber stresses under mechanical or thermomechanical loads. For composites under thermomechanical load, both in-phase and out-of-phase fatigue are modeled. The implications for life prediction for fiber-reinforced metal matrix composites are discussed.