Structure and micro-computed tomography-based finite element modeling of Toucan beak.

Bird beaks are one of the most fascinating sandwich composites in nature. Their design is composed of a keratinous integument and a bony foam core. We evaluated the structure and mechanical properties of a Toucan beak to establish structure-property relationships. We revealed the hierarchical structure of the Toucan beak by microscopy techniques. The integument consists of 50 μm polygonal keratin tiles with ~7.5 nm embedded intermediate filaments. The branched intermediate filaments were visualized by TEM tomography techniques. The bony foam core or trabecular bone is a closed-cell foam, which serves as a stiffener for the beak. The tridimensional foam structure was reconstructed by μ-CT scanning to create a model for the finite element analysis (FEA). The mechanical response of the beak foam including trabeculae and cortical shell was measured in tension and compression. We found that Young's modulus is 3 (S.D. 2.2) GPa for the trabeculae and 0.3 (S.D. 0.2) GPa for the cortical shell. After obtaining the material parameters, the deformation and microscopic failure of foam were calculated by FEA. The calculations agree well with the experimental results.