AN EVALUATION OF FIBER-REINFORCED TITANIUM MATRIX COMPOSITES FOR ADVANCED HIGH-TEMPERATURE AEROSPACE APPLICATIONS

The current capabilities of continuous silicon-carbide fiber-reinforce d titanium matrix composites (TMCs) are reviewed with respect to appli cation needs and compared to the capabilities of conventional high-tem perature monolithic alloys and aluminides. In particular, the properti es of a first generation titanium aluminide composite, SCS-6/Ti-24Al-1 1Nb, and a second-generation metastable beta alloy composite, SCS-6/TI METAL 21S, are compared with the nickel-base superalloy IN100, the hig h-temperature titanium alloy Ti-1100, and a relatively new titanium al uminide alloy. Emphasis is given to life-limiting cyclic and monotonic properties and to the influence of time-dependent deformation and env ironmental effects on these properties. The composite materials offer a wide range of performance capabilities, depending on laminate archit ecture. In many instances, unidirectional composites exhibit outstandi ng properties, although the same materials loaded transverse to the fi ber direction typically exhibit very poor properties, primarily due to the weak fiber/matrix interface. Depending on the specific mechanical property under consideration, composite cross-ply laminates often sho w no improvement over the capability of conventional monolithic materi als. Thus, it is essential that these composite materials be tailored to achieve a balance of properties suitable to the specific applicatio n needs if these materials are to be attractive candidates to replace more conventional materials.