ABSTRACT
Metal matrix composites (MMCs) can be constructed with a wide range of reinforcements, e.g., continuous fibers of large (150 IJ.m) and small (10 IJ.m) diameter, short fibers (3 IJ.m diameter), whiskers (<l1-1m diameter) with aspect ratios <50:1, and finally particles in the size range 3-100 IJ.m. These reinforcements are usually of high elastic modulus and low density, and this means that they are usually ceramic oxides, carbides, boron, or carbon. On occasion, e.g., for some high-temperature applications, metal wires such as tungsten have been employed. Uniaxial reinforcement, with continuous fibers, is frequently considered as the transverse properties of MMCs are usually somewhat better than with polymer-based composites. Nevertheless, examples of laminate construction in MMCs with 45° or 90° plies are to be found. Some degree of whisker or shortfiber alignment is possible with certain types of manufacture, e.g., in extruded shapes. All of these factors have an influence on fatigue properties as previous reviews have shown (Hancock, 1974; Gerold, 1988).
