Ply Curving Termination to Suppress Delamination in Composite Ply Drop-Off

Composite tapered sections with ply drop-off are prone to delamination due to stress concentration at the edge of the terminated 0° plies. Currently quite gradual taper angle is used in aircraft composites to suppress delamination, which leads to weight increase. Structural modification that can suppress the stress concentration is necessary to realize further-optimized lightweight structures with steeper taper angles. This study proposes a new approach called “ply curving termination (PCT)” in which local fiber orientation is modified at the edge of the terminated 0° plies. The curved area has significantly low stiffness and thus the stress concentration at the ply edge is suppressed. This paper reports the numerical analysis and experiment to validate the effectiveness of this new concept. In addition, suppression of edge delamination by PCT is also demonstrated.