JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS 9 (2012) 1–8 Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/jmbbm Research paper Structure and micro-computed tomography-based finite element modeling of Toucan beak Yasuaki Seki a , Mason Mackey b , Marc A. Meyers a,∗ a Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093, USA b National Center for Microscope and Imaging Research Facility, University of California, San Diego, La Jolla, CA 92093, USA ARTICLE INFO Article history: Received 10 June 2009 Received in revised form 21 July 2011 Accepted 13 August 2011 Published online 5 September 2011 ABSTRACT 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. c ⃝ 2011 Elsevier Ltd. All rights reserved. 1. Introduction Toco Toucan (Ramphastos toco) and other avian species like Hornbill have long and thick beaks, primarily used for foraging and fencing activities. In order to tolerate such activities, the beak maintains sufficient rigidity with a light-weight structure. The beak consists of an integument (rhamphotheca) and a closed-cell bony foam. In previous studies, Seki et al. (2005, 2006) have shown that the mi- croscopic structure of the integument consists of overlap- ping polygonal keratin tiles. The keratin tiles consist of a keratin matrix and 7.5 nm keratin fibers, intermediate fil- aments IF (Seki et al., 2010). However, the detailed config- ∗ Corresponding author. Tel.: +1 858 534 4719; fax: +1 858 534 5698. E-mail address: mameyers@ucsd.edu (M.A. Meyers). uration or shape of keratin fibers was still unknown. We used TEM tomography techniques to reveal the arrange- ment of IF. The rigidity of the beak is mechanically en- hanced by the foam core as evidenced by the resistance to buckling of the beak due to the synergism between the integument and the bony foam (Seki et al., 2005). Macro- scopically, the mechanical failure of the beak and the beak foam in compression (Seki et al., 2006) and bending (Fec- chio et al., 2010) was studied by FEA. The experimental re- sults and FEA exhibited a good agreement in predicting the deformation and failure of beaks. However, the deforma- tion models lack microscopic aspects of mechanical failure of the foam. We have employed μ-CT scanning techniques 1751-6161/$ - see front matter c ⃝ 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jmbbm.2011.08.003