MODEL CERAMIC FIBER-REINFORCED GLASS COMPOSITES - RESIDUAL THERMAL-STRESSES

The residual thermal stresses and strains in a variety of ceramic fibre-reinforced glass-matrix composites have been determined using Raman spectroscopy. it is possible to measure the thermal strains in such composites from the magnitude of stress- or strain-induced Raman band shifts in the fibres. Model single ceramic fibre/glass composites using both Nicalon SiC and PRD-166 alumina-zirconia fibres in both Pyrex and soda-lime-silicate glasses were produced at different fabrication temperatures and the residual fibre strains were estimated using Raman spectroscopy. The measured values of fibre strain were found to compare well with those calculated analytically and the fabrication temperature was not normally found to influence the level of residual fibre strain. In the case of Nicalon-reinforced Pyrex, however, large thermal strains were induced by heat-treating the composites at elevated temperatures due to crystallization of the glass matrix, which put the fibres into axial compression.