The influence of loading levels, temperature and environment on fibre failure during the fatigue of an SiC fibre reinforced Ti-MMC

摘要

The fatigue crack propagation characteristics of Ti-6Al-4V reinforced with SM 1240 SiC fibres have been investigated under a number of different loading conditions and at elevated temperatures of 300 and 500℃, in air and in vacuum. Both the initial applied stress intensity factor range (ΔK) and the initial applied maximum stress intensity factor (K_(max)) have been found to be important factors, which determine whether the initial loading conditions cause catastrophic failure of the specimen, or whether the bridging fibres in the wake of the crack reduce the effective value of ΔK at the crack tip by an amount sufficient to cause the fatigue crack to arrest. At the elevated temperatures of 300 and 500℃ in air, crack growth resistance decreases progressively with temperature increase. Tn vacuum, however, a decrease in fatigue crack growth resistance is seen only at a test temperature of 500℃.