1993 Volume 42 Issue 472 Pages 52-58
The effects of stress ratio on tension-tension fatigue behavior and mode I delamination fatigue crack propagation behavior were investigated on two kinds of unidirectional CF/epoxy laminates (Toray T300/#3601 and T800/#3631). The analysis of the equivalent stress intensity range proposed by the authors showed that the contribution of maximum stress was large in delamination fatigue crack propagation. A similar analysis was applied to the results of the tension fatigue tests. The contribution of maximum stress was also large in tension fatigue fracture. The tension fatigue fracture was mainly caused by longitudinal fracture. The similarity in fracture surface between tension fatigue fracture and delamination fatigue fracture for the T300/#3601 laminates was indicated by microscopic observations. For the T800/#3631 laminates, there was a difference between the fracture mechanism of tension fatigue fracture and that of delamination fatigue fracture. The degree of the contribution of maximum stress was correlated to the fracture mechanisms of tension fatigue fracture and delamination fatigue crack growth.
