Effect of cycles on flexural fatigue strength for 2D C/C composites

The effect of cycles on the flexural fatigue strength for 2D carbon-felt C/C composites at room temperature was studied under the sinusoidal loading frequency of 10 Hz and stress ratio of 0.1.The microstructure of the pyrolytic carbon and the morphology of the fractured surfaces of the samples before and after being fatigued were observed by polarized light microscope(PLM) and SEM. The results show that the pyrolytic carbon consists of smooth laminar and isotropic structure. The fatigue limit of 2D carbon-felt reinforced carbon composites is found to be 76.5 MPa, 90% of the static flexural strength. The residual flexural strength and toughness of the materials after being fatigued are improved. The fiber/matrix interface bonding strength is weaken during fatigue-loading, while collaborative carrying capacity of fiber is improved. Therefore, the fatigue strength-enhancing behavior of C/C composites appears.