Experimental and numerical study on the flexural mechanical properties of bioinspired composites with suture structures

Composite structures inspired by the suture line in the beak of woodpeckers, which is composed of stiff material (mimicking keratin) and compliant material (mimicking collagen), are proposed in this article. The flexural mechanical properties as well as the deformation and failure modes are investigated combining experiments and simulations, which are also compared with conventional laminated structures. First, three-point bending test is performed to characterize mechanical properties such as flexibility, stiffness, strength, and energy dissipation. Experimental results confirm that the suture structure affects the flexural properties significantly. Then, a finite element (FE) model is established to present the strain and stress fields inside the composite beams. The strain distribution demonstrates a shear mechanism in suture structures to dissipate energy, while the stress distribution reveals that the soft layers act as shock absorbers to release stress transmitted through the structure. At last, the failure mode and toughening mechanism of the composite structures is discussed. The mechanism responsible for the mechanical performance of biological structures can be generalized to design architectures with customized mechanical performances.