Damage accumulation during isothermal fatigue of Ti-SiC laminates

Autor: P. Lipetzky, George J. Dvorak, N.S. Stoloff
Rok vydání: 1996
Předmět:
Zdroj: Scripta Materialia. 35:1089-1094
ISSN: 1359-6462
DOI: 10.1016/1359-6462(96)00255-2
Popis: Titanium-based composites have been under investigation for the last three decades because titanium alloys have the highest strength-to-weight ratio of all common structural metals. The high strength at low to intermediate temperatures (up to 550 C), coupled with a high impact fracture energy, makes these materials candidates for applications such as gas turbine fan blades. Perhaps more important for this application is the fact that Ti composites can have high stiffness, which raises the critical vibration frequencies and lowers the necessary blade thickness and mass. Efforts to reinforce these alloys began with the inclusion of boron filaments. However, complications arose due to reactivity between Ti and the fibers. Since that time compatibility problems have been overcome by either altering the matrix composition or coating the fibers. Subsequently, interest has turned to continuous SiC reinforcements with a variety of fiber diameters, volume fractions and coatings. A full description of the experimental test methods as well as the sample manufacturing procedure was given previously. Therefore, only a brief summary is given here. Fiber volume fraction for all lay-ups was approximately 30%. Prismatic coupons were subjected to a cyclic tensile load history (load ratio = 0.1) with frequencies of 0.001 Hz and 0.1more » Hz. Temperature in the entire gauge section was held constant at 650 C. Strain was measured directly from the sample using a high-temperature extensometer. Following failure, portions of the gauge section were mounted in epoxy and polished by hand on conventional diamond wheels for metallographic analysis. Because the composite section was inclined at a small angle relative to the grinding surface, a wedge of material was removed during grinding so that features from a range of depths could be viewed simultaneously.« less
Databáze: OpenAIRE
Externí odkaz: