Nanoindentations on Conch Shells of Gastropoda and Bivalvia Molluscs Reveal Anisotropic Evolution Against External Attacks

Abstract

Nanoindentation method has been used to explore, at the nanoscale, the mechanical properties of four different representative types of conch shells belonging to the two biggest classes of molluscs, Gastropoda and Bivalvia, in order to compare nanohardness and Young's modulus with respect to the microstructural anisotropic architectures. For the experimental tests a Nano Indenter XP (MTS Nano Instruments, Oak Ridge TN) has been used. The mechanical tests have been carried out on the inner and outer surfaces of the shells, as well as on their cross-section, near to the inner/outer surfaces and in the middle layer. The results confirm the three layered anisotropic architecture of the investigated conchs. On each of these 5 surfaces, 2 x 5 indentations have been performed at different maximum depth: from 250 nm to 4 microm, with a step of 250 nm, for a total of 3200 tests. The numerous observations have been analysed applying an ad hoc modification of the Weibull Statistics, suggesting a natural evolution of the shells against external attacks.

Microstructure Analysis and Chemical and Mechanical Characterization of the Shells of Three Freshwater Snails

“…The present results were somehow constant with the nanoindentation for gastropod shells done previously. 69 , 71 The arrangement pattern of calcium carbonate crystal plate in an horizontal array is very common and clear in the FE-SEM photomicrograph of each snail shell sample. Due to this layered structure, the nanohardness and elastic modulus showed load independency.…”

“…Due to this layered structure, the nanohardness and elastic modulus showed load independency. 71 − 73 …”

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Finite Element Modeling Application in Forensic Practice: A Periprosthetic Femoral Fracture Case Study

“…The structural analysis of skeletal body elements and of biomechanical systems consisting of a bone element coupled to a prosthesis, an implant or a fracture synthesis device, can be performed both numerically and experimentally. There are indeed many examples of clinical problems which have moved from a qualitative assessment to a quantitative evaluation thanks to computational modeling (Vitale et al, 2008;Zanetti and Bignardi, 2013;Zanetti et al, 2017Zanetti et al, , 2018aAldieri et al, 2018b;Calì et al, 2018;Putzer et al, 2018;Terzini et al, 2018Terzini et al, , 2019Putame et al, 2019), to the application of classical experimental methods of structural analysis in the evaluation of the efficacy of procedures or surgical techniques (Bresciano et al, 2005;Menicucci et al, 2006;Zanetti and Audenino, 2010;Zanetti et al, 2012aZanetti et al, , 2018bBoero Baroncelli et al, 2013;Manzella et al, 2013Manzella et al, , 2016Bignardi et al, 2018), or to the evaluation of the mechanical characteristics of the materials used at different scales of investigation (Peluccio et al, 2007;Bignardi et al, 2010;Zanetti et al, 2012b;Terzini et al, 2016a,b;Aldieri et al, 2018a). Computational modeling, more than experimental one, finds natural application in forensic practice, as samples are often unavailable for experimental investigations.…”