Effect of interface damage on fatigue crack growth for SiC fiber-Reinforced Ti-15-3 matrix composite

摘要

The fatigue crack growth behavior in SiC (SCS-6) fiber reinforced Ti-15-3 matrix alloy composite subjected to a constant tension-tension loading mode was studied using single edge specimen in 2 x 10~-3 Pa vacuum at 293 and 823K, with a frequency of 2 Hz, and a stress ratio of R=0.1. Direct measuremdent of the fatigue crack length, and the crack opening displacement along the crack wake during the test were carried out by scanning electron microscope (SEM). The increase in the test temperature was found to lead to a decrease in the fatigue crack growth rate. Trhe degradation of bridging fibers in the crack wake was severe for T=293K, and this behavior was dependent of the test temperature. Fine particle-like debris was found on the fracture surface in the region of crack propagation in specimens tested at T=823K. This is thought to be caused by the interface wear behavior. The crack opening displacement along the crack wake tested at T=823K decreased with increasing crack length, and this tendency is dependent on the applie dstress range. The associated increase in the crack tip shielding is explained on the basis of the crack closure due to the matrix relaxation by fatigue creep and the interface wear behavior.