FATIGUE CRACKING IN FIBER-REINFORCED METAL-MATRIX COMPOSITES UNDER MECHANICAL AND THERMAL LOADS

This article reviews micromechanical models developed for fatigue crac king in fiber reinforced metal matrix composites under mechanical and thermal lends. Emphasis is placed on the formulae and design charts th at can quantify the fatigue crack growth and fiber fracture. The compo site is taken to be linear elastic, with unidirectional aligned fibers . Interfacial debonding is assumed to occur readily, allowing fibers t o slide relative to the matrix resisted by a uniform shear stress. The fibers therefore bridge any matrix crack that develops. The crack bri dging traction law includes the effect of thermal expansion mismatch b etween the fiber and the matrix and a temperature dependence of the fr ictional shear stress. Predictions are made of the crack tip stress in tensities, matrix fatigue crack growth, and maximum fiber stresses und er mechanical or thermomechanical loads. For composites under thermome chanical load, both in-phase and out-of-phase fatigue are modeled. The implications for life prediction for fiber-reinforced metal matrix co mposites are discussed.