Fatigue Strength of Notched Specimen of Machinable C⁄C Composites

The fatigue strengths in notched specimens of C⁄C composites were investigated. The plate of C⁄C composites using fine-woven carbon fiber laminates with =0⁄90°direction was used for testing. The phenomenon of crack growth behavior and the shear damage in the fiber bundle was discussed. Slits of several sizes were cut on both sides of a test section and different sizes of slit length were chosen. Also, specimen with blunt-notches was used to compare the fatigue strength. The weakest fatigue limit was obtained in the case of specimens with blunt-notch. However, the stress concentration factor of that is smaller than that of slit specimens. The relationships between fatigue strengths and specimen shapes were analyzed by stress distribution and stress intensity factor,kI. The effect of slit configuration on fatigue strength was then discussed regarding both the experimental and calculated consequences. Consequently, it was discussed that fatigue strength of present specimens was determined depending on the damage conditions in the vicinity of notch and on the crack initiation behavior.