Low cycle fatigue tests were performed on Ti-24Al-11Nb titanium aluminide composite unidirectionally reinforced with SCS-6 fiber. (SCS-6 is a SiC-based fiber manufactured by Textron-SMD in Lowell, Massachusetts.) The effect of circular holes onthe fatigue life of this composite system was measured with respect to fiber orientation, temperature, and frequency. Longitudinal and transverse specimens with and without holes were tested at 26°C and 649°C at 0.33 Hz. In addition, longitudinal specimens were also tested at 30 Hz and 649°C to determine the effect of frequency.
A degradation in fatigue life due to the presence of holes was observed in specimens loaded in the fiber direction (longitudinally). This effect is independent of frequency. The notch sensitivity factor, Q, associated with the reduction in life ranges from 0.33 to 0.50 over the range of temperature tested.
The specimens oriented with the load axis perpendicular to the fiber direction (transverse) demonstrated no sensitivity of fatigue life to the presence of holes at room temperature but did possess a finite sensitivity at 649°C with a Q=0.45.