Physical properties and life prediction of TMC at elevated temperatures

Abstract

Abstract Mechanical performance of titanium matrix composites degrades at elevated temperatures because of the changes in physical properties of the composites (i.e. matrix oxidation, embrittlement and phase transformation). These physical properties of the composites should be taken into account in a life prediction model. The present study was conducted to improve an existing life prediction model (local fiber stress failure model). To achieve this goal, isothermal fatigue tests were performed on [0/±45/90] s SCS-6/Timetal 21S composite at temperatures 400 and 500 °C, and with hold times. The composite lives at 400 and 500 °C increased with increase in hold time. It was observed that the matrix oxidation was accelerated under applied stress amplitude. In addition, the measurement of the surface oxide thickness suggested that the oxidation was much easier and faster at 500 °C than at 400 °C. A modification was made on the life prediction model. Since the oxidation was shown to have a significant effect on the composite life, it was factored into the model. The modified model produced a good correlation between modified single parameter value and the number of cycles to failure.