Inside a feather: laminar layup varies around and along bird feather shafts

Abstract

Feathers have been evolving for more than 130 million years under selection pressures to become light, stiff and strong. However, a detailed investigation into their material structure (and properties) is still lacking. Previously, using nanoindentation and μCT, we have shown that feather shafts are fibrous laminar composites and that their structure varies between species. Here we show a feather’s structure also varies around its circumference and along its length. We present the first synchrotron radiation computed tomography (SR-CT) dataset, from which we infer fibre orientation inside the feather shaft cortex. Scans of different locations on the shaft show that the number of laminae and fibre alignment within feather shafts of the heaviest flying bird, the Swan, are not fixed; they vary both around the circumference of the shaft and along its length. Our work opens a new perspective on a research question in avian biology which has remained unanswered for more than 30 years: what is the modulus of feather-keratin? To answer this question, one needs to take into account not only the shaft’s geometry but also its layup.

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Identifiers

ORCID for Christian Laurent: orcid.org/0000-0002-2946-9705

ORCID for Philipp Schneider: orcid.org/0000-0001-7499-3576

ORCID for Richard Boardman: orcid.org/0000-0002-4008-0098

ORCID for Richard Cook: orcid.org/0000-0002-2468-5820

ORCID for Roeland De Kat: orcid.org/0000-0002-6851-4409

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