Impact protection performance of composite biomimetic structure inspired by woodpecker beak and turtle shell curvature

To improve the energy absorption and cushioning performance of lightweight protective structures under impact loading, a composite biomimetic core structure integrating the gradient curvature of a woodpecker beak and the dome-like curvature of a turtle shell is proposed. Typical curvature features are extracted to construct a composite curved unit cell, and two configurations, including array and strip structures, are developed. An impact finite element model is established using ABAQUS/Explicit, and comparisons are conducted with conventional honeycomb structures. The results show that the composite curved structures exhibit a stable progressive collapse mode during impact. The curved geometry alters the load transfer path and enables gradual stress diffusion along the surface, thereby reducing local stress concentration and enhancing cooperative deformation. Compared with the honeycomb strip structure, the composite curvature strip structure reduced the peak clay stress by 33.7% and the maximum back-plate intrusion displacement by 14.8%, while the maximum clay energy decreased from 10.22 J to 8.26 J. For the composite curvature array structure, the maximum clay stress, maximum back-plate displacement, and maximum clay energy were 15.65 MPa, 0.23 mm, and 13.08 J, respectively. The results indicate that the composite curvature structure significantly enhances impact protection performance through the synergistic effect of macroscopic load diffusion and local progressive collapse.