Isotropic microscale mechanical properties of coral skeletons

Luca Pasquini, Alan Molinari, Paola Fantazzini, Yannicke Dauphen, Jean Pierre Cuif, Oren Levy, Zvy Dubinsky, Erik Caroselli, Fiorella Prada, Stefano Goffredo, Matteo Di Giosia, Michela Reggi, Giuseppe Falini

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Scleractinian corals are a major source of biogenic calcium carbonate, yet the relationship between their skeletal microstructure and mechanical properties has been scarcely studied. In this work, the skeletons of two coral species: solitary Balanophyllia europaea and colonial Stylophora pistillata, were investigated by nanoindentation. The hardness HIT and Young's modulus EIT were determined from the analysis of several load-depth data on two perpendicular sections of the skeletons: longitudinal (parallel to the main growth axis) and transverse. Within the experimental and statistical uncertainty, the average values of the mechanical parameters are independent on the section's orientation. The hydration state of the skeletons did not affect the mechanical properties. The measured values, EIT in the 76-77 GPa range, and HIT in the 4.9-5.1 GPa range, are close to the ones expected for polycrystalline pure aragonite. Notably, a small difference in HIT is observed between the species. Different fromcorals, single-crystal aragonite and the nacreous layer of the seashell Atrina rigida exhibit clearly orientation-dependent mechanical properties. The homogeneous and isotropic mechanical behaviour of the coral skeletons at the microscale is correlated with the microstructure, observed by electron microscopy and atomic force microscopy, and with the X-ray diffraction patterns of the longitudinal and transverse sections.

Original languageEnglish
Article number20150168
JournalJournal of the Royal Society Interface
Volume12
Issue number106
DOIs
StatePublished - 6 May 2015

Bibliographical note

Publisher Copyright:
© 2015 The Author(s) Published by the Royal Society. All rights reserved.

Funding

FundersFunder number
European Research Council

    Keywords

    • Biomaterial
    • Corals
    • Mechanical properties
    • Microstructure

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