Improving fatigue characteristics of ply drop-off in composite laminate with ply curving termination

Ply drop-off is a weak point of a tapered composite laminate, where stress concentration occurs and delamination initiates. By suppressing delamination from the ply drop-off, more optimized structural design and further weight reduction are possible. Ply Curving Termination (PCT), which locally changes the fiber direction at the edge of the dropped ply, is one of the promising delamination suppression mechanisms. To improve the technical maturity of PCT, this study conducted tensile fatigue tests using asymmetric taper configuration. Damage initiation, delamination propagation, and final failure were evaluated in detail by changing the PCT fiber angle and loading level, confirming that large PCT angles are effective in improving the fatigue properties of tapered laminates and that controlling the location of initial damage is necessary to maximize the effectiveness of PCT. Based on the findings, an effective design guideline for tapered laminates with PCT was presented.