Interphase behavior of titanium matrix composites at elevated temperature

This paper examines the effect of temperature and thermal exposure on the interphase behavior of continuous fiber reinforced titanium metal matrix composites. The system considered is SCS-6/Timetal-21S. Elevated temperature fiber push-out tests were conducted to determine the effect of test temperature on interphase shear properties. Corresponding variations of debonding shear strength and frictional shear stress with test temperature are presented and discussed. Thermal exposure, both in a vacuum and an air environment, has been conducted on specimens, with temperatures up to 650 °C and exposure times of up to 100 h. The resulting size and composition of the interphase have been examined. Fiber push-out tests were carried out at room and elevated temperature on the aged specimens. Results are discussed in terms of the influence of relaxation and oxidation on the debond shear strength. Using the experimentally determined interphase shear properties, the interphase toughness has been calculated and discussed in relation to interface decohesion models.