Turtle shells comprising of cortical and trabecular bones exhibit intriguing mechanical properties. In this work, compression tests were performed using specimens made from the carapace of Kinixys erosa turtle. A combination of imaging techniques and mechanical testing were employed to examine the responses of hierarchical microstructures of turtle shell under compression. Finite element models produced from microCT-scanned microstructures and analytical foam structure models were then used to elucidate local responses of trabecular bones deformed under compression. The results reveal the contributions from micro-strut bending and stress concentrations to the fractural mechanisms of trabecular bone structures. The porous structures of turtle shells could be an excellent prototype for the bioinspired design of deformation-resistant structures.
Nacre, also known
as mother of pearl, possesses extraordinary mechanical
properties resulting from its intriguing hierarchical brick-and-mortar
microstructures. Despite prior studies, interactions between nanoasperities
during sliding still need to be elucidated. In this study, we measure
slip events between nanograins of microlayers at high temporal resolution
during torsion-induced sliding. We model the slips as avalanches caused
by interactions of atoms on nanograin surfaces, from which power laws
and scaling functions describing statistics and dynamics of slip events
are studied. The largest avalanche occurs when nanograins leave each
other after the maximum contact. The agreement between measurements
and predictions shows that avalanches act essentially in the inhomogeneous
sliding of nacreous tablets. Further insights into nanofriction provided
in this work may lead to the development of nanoscale tribological
systems.
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