Re: Toucan Beak Citation and Abstract

[Phil Bigelow <bigelowp@juno.com>]

The "organic glue" may be an important  factor in contributing to the
strength of the beak.  I haven't read the paper yet.  Is the glue some
type of modified collagen or is it more like the glue barnacles use to
attach themselves to rocks?  If its new to science and the stuff can be
synthesized, I'll bet the patent lawyers will be working overtime filling
out the necessary paperwork.

<pb>
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On Thu, 01 Dec 2005 13:26:08 -0500 "Andrew A. Farke"
<andyfarke@hotmail.com> writes:
> Following the post from Richard Travsky, the citation and abstract 
> for 
> 
> ***************
> Seki, Y., M. S. Schneider, and M. A. Meyers. 2005. Structure and 
> mechanical
> behavior of a toucan beak. Acta Materialia 53:5281-5296.
> 
> The toucan beak, which comprises one third of the length of the bird 
> and yet
> only about 1/20th of its mass, has outstanding stiffness. The 
> structure of a
> Toco toucan (Ramphastos toco) beak was found to be a sandwich 
> composite with
> an exterior of keratin and a fibrous network of closed cells made 
> of
> calcium-rich proteins. The keratin layer is comprised of superposed
> hexagonal scales (50 [mu]m diameter and 1 [mu]m thickness) glued 
> together.
> Its tensile strength is about 50 MPa and Young's modulus is 1.4 GPa. 
> Micro
> and nanoindentation hardness measurements corroborate these values. 
> The
> keratin shell exhibits a strain-rate sensitivity with a transition 
> from
> slippage of the scales due to release of the organic glue, at a low 
> strain
> rate (5 x 10-5/s) to fracture of the scales at a higher strain rate 
> (1.5 x
> 10-3/s). The closed-cell foam is comprised of fibers having a 
> Young's
> modulus twice as high as the keratin shells due to their higher 
> calcium
> content. The compressive response of the foam was modeled by the
> Gibson-Ashby constitutive equations for open and closed-cell foam. 
> There is
> a synergistic effect between foam and shell evidenced by experiments 
> and
> analysis establishing the separate responses of shell, foam, and 
> foam +
> shell. The stability analysis developed by Karam and Gibson, 
> assuming an
> idealized circular cross section, was applied to the beak. It shows 
> that the
> foam stabilizes the deformation of the beak by providing an elastic
> foundation which increases its Brazier and buckling load under 
> flexure
> loading.
> 
> (abstract available at sciencedirect.com)
> 
> ***************
> 
> This paper has a bit of relevance for all those who are interested 
> in
> modeling dinosaurs and the like--another nice set of material 
> properties to
> utilize. A nice little piece of experimental functional morphology.
> 
> Andy 
> 
> 


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