Contact Mechanics of Fish Scale Inspired Exoskeletal Components on a Nonlinear Elastic Substrate

Abstract

The contact mechanics of structures with exoskeletal components deviate significantly from classical Hertzian and non-linear models. In the case of fish scale inspired samples under blunt indentation loading these factors are inherently tied to both the size of the indenter and the scales' distribution and orientation. Control of these geometric parameters provides a pathway to tailor the properties of surfaces for better grip, damage mitigation and controlled deformation. This study explores the response of a substrate with stiff scales protruding from its surface, which is comprised of a soft elastomeric material with properties typical of those in soft robotics applications. It is found that the exoskeletal components amplify the nonlinearly of the system by artificially increasing the effective Hertzian contact area, which alters the contact stiffness and breaks the symmetry of the load across the surface. These effects are quantified using a combination of numerical modeling, finite element (FE) computation and experimental 3D Digital Image Correlation (DIC). While previous works have focused on biological fish scales, fully embedded scale composites and perforation studies, this study investigates and develops a numerical model to quantify the contact behavior of nonlinear elastic substates with exoskeletal scale structures.