THE EFFECT OF FIBER ORIENTATION ON FATIGUE-CRACK PROPAGATION IN SCS-6TI-15-3 COMPOSITES

The fatigue crack propagation behavior of [0/90]s and [0/+/-45]s SCS-6 /Ti-15-3 laminates at room temperature was studied and compared with t hat of a [0]6 laminate. The testing was conducted in a tension-tension mode on specimens with a chevron notch perpendicular to the 0-degrees surface layer. The maximum applied stress intensity ranged from 20 to 30 MPa m1/2. The fatigue crack growth rates at various applied stress intensity levels were measured and the fatigue damage mechanisms were examined. It was found that fatigue crack damage in angle-ply SCS-6/T i-15-3 laminates is much more complex than that identified in their un idirectional counterparts. The primary crack which originated from the notch interacted with secondary cracks, resulting in catastrophic fai lure of the laminate. Also, the direction of fatigue crack growth and the final crack length differed in each layer of the angle-ply laminat es.