INFLUENCE OF MICROSTRUCTURE AND STRAIN RATE ON THE COMPRESSIVE STRENGTH OF WHISKER-REINFORCED CERAMIC MATRIX COMPOSITES

The compressive strength of pyroceramic reinforced with a wide variety of SiC whiskers was characterized at loading rates which range from quasi-static to dynamic. It was found that strength is inversely related to whisker size, and essentially strain rate insensitive. The same strain rate independence was obtained for unreinforced matrix, but the strength of the latter lies below that for small (less-than-or-equal-to 1-mu-m diameter) whisker-reinforced composites, and above that for large (approximately greater-than 3-mu-m diameter) whisker material. Whisker/crack interaction and (to a lesser extent) whisker pull-out seem to be responsible for the beneficial influence of small whiskers, while the apparently detrimental large whiskers serve as microcrack-nucleating inclusions.