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Limpet teeth contain a desirable combination of material properties: they are auxetic (i.e., they have a negative Poisson’s ratio) and have high stiffness and strength. In contrast, synthetic auxetic structures presented in the literature to date are typically accompanied by low stiffness. Hence, limpet teeth microstructures are an attractive candidate for bio-inspired synthetic structures that have both auxeticity and high stiffness. The microstructure consists of iron oxide hydroxide crystal nanorods embedded in an amorphous hydrated silica matrix. Moreover, a portion of the nanorods are arranged into oriented bundles which are surrounded by a chiral arrangement of the remaining nanorods. Many synthetic structures achieve auxeticity by means of a similar chiral arrangement of rods. However, such structures are typically continuous, whereas the limpet teeth structures are not. In this work, a mechanistic description of such microstructural arrangements is provided by means of a computational parametric study of idealized microstructures comprising bimodal particle reinforcements with chiral confinement. The influence of microstructural geometry on the effective mechanical properties is investigated by varying parameters such as particle shape, bundle design, rod orientation, and others. It is shown that chiral rods that impinge on the central bundle are crucial for auxeticity and high material stiffness.
Alheit et al. (Mon,) studied this question.