CREEP AND FATIGUE BEHAVIOR OF SIC FIBER-REINFORCED SIC COMPOSITE AT HIGH-TEMPERATURES

Tensile creep and tension-tension fatigue of SiC fiber reinforced SiC composite were investigated in argon at 1000 and 1300 degrees C. Time- dependent (creep) strains under cyclic loading are much larger than th ose under constant load. However, the minimum creep strain rates under cyclic loading are similar to those under constant load at 1000 degre es C and lower than those under constant load at 1300 degrees C. All t he data of the minimum creep strain rates versus time to rupture under both cyclic loading and constant load fall on the same line, i.e., th e relations fit Monkman-Grant relationship. This means that creep cont rols the rupture life under cyclic loadings at high temperatures. At h igh stresses, the creep crack propagation paths are similar to fatigue crack propagation. However, at low stresses, more 0 degrees fibers we re broken in the way of flush with the matrix under creep load than th at under fatigue load. (C) 1997 Elsevier Science S.A.