Evaluation of Fiber/Matrix Interfacial Strength of Neutron irradiated SiC/SiC Composites Using Hysteresis Loop Analysis of Tensile Test

摘要

Advanced SiC/SiC composites composed of highly-crystalline and near-stoichiomctric SiC fibers, SiC matrix by CVI method, and PyC interphase were irradiated up to 1.0 X 10~(25) n/m~2 (E > 0.1 MeV, approx 1 dpa) at 1273K. Unload/reload cyclic tensile test and hysteresis loop analysis were carried out in order to identify neutron irradiation effects on interfacial properties of advanced SiC/SiC. The composites exhibited good irradiation resistance in ultimate tensile strength (approx 10 percent increase), but there were slight reduction of elastic modulus and proportional limit stress (PLS) (approx 10 percent). Wider hysteresis loops and lower gradient of the curves beyond PLS from the strain-stress curves, and longer pullouts of fiber from the SEM observation were observed, which imply weaker F/M interactions after neutron irradiation. From the hysteresis loop analysis, degradation of interfacial sliding stress and negative increment of misfit stress after neutron irradiation were obtained.