Effect of interface strength on metal matrix composites properties

Fundamental understanding of fiber–matrix interface phenomena is central to the study of mechanical performance of fiber composites and nanocomposites of all kinds. Several experimental techniques have been successfully employed to measure quantitatively the interface bond strength in MMCs, or at least indicate qualitatively the changes in the interface bond quality arising from the variations in composite processing conditions, fiber surface modifications, etc. The experimental methods discussed here include fiber pull-out/push-out tests, fiber fragmentation test, bimaterial delamination tests, cruciform transverse tensile tests, and nanoindentation. Among these techniques, the fiber push-out test and the cruciform transverse tensile test have received the most attention for use with MMC systems. The properties measured and the phenomena observed at the interface region are unique to each fiber–matrix system, as are the molecular conformation, elemental distribution, and thermo-mechanical compatibility. Due to the wide range of fiber and matrix materials that are available to construct a composite, no general conclusion can be drawn about the correlations between the microscopic interface phenomena and the macroscopic properties of composites. Nevertheless, the following points have been identified with regard to the influences of the nature of the interface on the performance of MMCs. 1. Cavitation or void formation and interface debonding are two principal failure mechanisms taking place at the interface region. There are contradicting requirements for these mechanisms to occur, though nucleation of voids often leads to massive interface debonding. 2. The degree of chemical reaction and the resulting reaction layer thickness have a significant effect on....