Creep-rupture lifetime distribution of boron fibers

Abstract

The purpose of this study is to evaluate the statistical properties of creep-rupture lifetime in boron fibers by using a time-dependent Weibull distribution, from the viewpoint of materials reliability engineering. Axial creep-rupture tests on boron fibers were carried out under several constant loads and constant loading rates in air at 300°C, and the relevant Weibull parameters were estimated from the lifetime and strength data obtained in the above tests. The results showed that the estimated lifetime distribution curves were not in good agreement with the experimental data at other applied loads. The SEM observation for the fracture surfaces indicated that the kind of defect causing the long-term rupture was completely different from that of the short-term rupture. Therefore, a mixed time-dependent Weibull distribution based on a mixed distribution model was proposed for evaluating the scatter of the creep-rupture lifetime data. It was proved that, finally, the distribution proposed here was suitably applicable for predicting the creep-rupture lifetime distribution of boron fibers.