Effect of matrix and fibre type on low cycle fatigue of [90]8 Sigma fibre reinforced titanium matrix composite

The low cycle fatigue behaviour of [90] fibre reinforced Titanium matrix composite has been examined. The fatigue lives of the TMC are inferior to those of the monolithic alloy, as a result of failure of weak fibre/matrix interfaces. Matrix fatigue cracks are observed but these do not initiate, as previously feared, at specimen machined edges. Rather, they originate in the bulk of the TMC. Of the three TMCs currently studied, Timetal 834/SM1140+ has consistently inferior fatigue lives. This is a result of a propensity for matrix cleavage failure at the lower test temperature, a weak fibre matrix interface, and a susceptibility to oxidation damage. A recently proposed model to predict the transverse creep lives of TMCs has been assessed.