Bend stress relaxation of advanced SiC-based fibers and its prediction to tensile creep

Abstract

Continuous SiC-based fibers are being considered as reinforcement for ceramic matrix composites (CMCs). Creep behavior of SiC-based fibers is a major concern for CMCs subjected to high temperature environment. However, there are significant difficulties in the experimental measurement of tensile creep for advanced SiC-based fibers because of their fine diameters. In this study, the bend stress relaxation (BSR) method was applied to investigate the creep behavior of advanced SiC-based fibers. The apparent activation energies of creep were calculated by a cross-cut method from the time–temperature dependence of stress relaxation parameter. The apparent activation energies of creep obtained in this work are in agreement with the activation energies of diffusion of silicon and carbon in β-SiC. Furthermore, the tensile creep was predicted from BSR data and compared with previous data. Prediction result showed good correlation between the BSR data and tensile creep data. The dominant creep mechanism is grain boundary sliding accommodated by diffusion in present test condition.