Deconvolution of the elastic properties of bivalve shell nanocomposites from direct measurement and finite element analysis

A new protocol has been devised for determining elastic properties of natural biocomposites in the form of bivalve shells under wet and dry conditions. Four-point bending on shell slices ofMytilus edulis, Ensis siliqua, andPecten maximusgive generally lower and more reliable values of Young’s modulus,E, than those in the literature from three-point bending, due to the more even distribution of strain. Finite element analysis of the prismatic microstructure ofPinna nobilis, obtained by X-ray tomography, shows that values ofE≈ 20 GPa can be understood in terms of the real microstructure containing a small proportion of organic matrix phase withE≈ 1 GPa and a dominant proportion of calcite withE≈ 90 GPa. Higher values ofEobtained by nanoindentation give results which are biased toward the properties of the carbonate phase rather than of the biocomposite as a whole.