FIBER CREEP RATE AND HIGH-TEMPERATURE PROPERTIES OF SIC SIC COMPOSITES/

Optimization of the high-temperature structural properties of continuo us silicon carbide fiber, silicon carbide matrix composites (SiC/SiC) requires a fundamental understanding of the relationship between fiber , matrix, and interface properties. Results of a study aimed at relati ng the fiber creep rate to the subcritical crack growth (SCG) rate and fracture properties of SiC/SiC composites have demonstrated that the crack growth rate in a bulk composite is controlled by the fiber creep rate. This result was demonstrated for Nicalon-CG and Hi-Nicalon fibe r reinforced material where a 100 degrees C shift in the creep strengt h of the fiber resulted in a similar shift in the crack growth rate of the composite. Irradiation enhanced creep of SiC fibers and matrix mu st also be considered in the performance assessment of SiC/SiC composi tes. An estimate of the impact of irradiation creep of SiC fibers on t he SCG of SiC/SiC will be presented. (C) 1998 Elsevier Science B.V. Al l rights reserved.