Off-Axis Fatigue Behavior and Its Damage Mechanics Modeling for Hybrid Composite GLARE 2

Fatigue behavior of unidirectional fiber-metal laminates GLARE 2 has been studied under various off-axis loading conditions. Tension-tension fatigue tests were performed for nine kinds of plain coupon specimens with different off-axis angles at room temperature. A non-dimensional effective stress implied by the classical static failure theories was applied as a fatigue strength parameter to the off-axis fatigue. Using the non-dimensional effective stress, a fatigue damage mechanics model was developed. Applicabilities of the classical composite fatigue failure models were evaluated on the basis of the observed off-axis S-N relationships. Off-axis fatigue stengths decreased significantly as the off-axial angles increased. Irrespective of the off-axis angles, almost linear S-N relationships were observed in the intermediate range of fatigue, and they were followed by apparent fatigue limits. The non-dimensional effective stress was found to be very useful to unify the off-axis fatigue data. The characteristics of the observed off-axis S-N relationships were described by the classical fatigue failure models. The predictive capability of the proposed fatigue damage mechanics model was almost comparable, which verified a potential applicability to fatigue life analyses for multidirectional laminates.