抄録
Notched off-axis fatigue behavior of CFRP laminate has been studied. Static and fatigue tests are performed at room temperature on unnotched (UN) and center-hole (CH) coupon specimens of a plain woven CFRP laminate for different fiber orientations as well as for different stress ratios. The static and fatigue strengths of notched specimens are lower than those of unnotched specimens, regardless of fiber orientation, but the degree of fatigue strength reduction is different depending on stress ratio as well as fiber orientation. Soft X-ray radiographs of notched specimens taken after fatigue loading show that a characteristic growth of fatigue damage. After tension-dominated fatigue loading, the damage due to fatigue develops in the form of matrix cracks from hole edges along fiber direction. The growth of damage at hole edges reduces stress concentration. Accordingly, the notch sensitivity decreases with cyclic loading to approach a notch insensitive fatigue behavior. Next, the notched off-axis fatigue life of the CFRP laminate is predicted using the notched fatigue life prediction method that was developed in an earlier study for on-axis fatigue life prediction. The off-axis fatigue lives predicted by means of the notched fatigue life prediction method are compared with the fatigue lives observed in this study. The predicted notched off-axis fatigue lives agree well with the experimental results, demonstrating the potential of the notched fatigue life prediction method.
