ACOUSTIC MICROSCOPY OF CERAMIC-FIBER COMPOSITES .1. GLASS-MATRIX COMPOSITES

The microstructure of Nicalon-reinforced borosilicate glass was studie d using scanning acoustic microscopy (SAM) and scanning electron micro scopy (SEM). Acoustic micrographs exhibited high contrast, and the for mation of Rayleigh-wave-interference fringes both within and around fi bres allowed the in-situ-fibre and matrix elastic moduli to be estimat ed. The matrix was found to have undergone partial devitrification res ulting in the formation of cristobalite. The presence of a high volume fraction of reinforcing fibres was found to have little effect on cri stobalite formation and distribution. The thermal expansion mismatch b etween beta-cristobalite to give rise to extensive microcracking aroun d individual cristobalite grains and partial fibre/matrix debonding.