The Mechanics and Multiphysics of Biomimetic Discrete Exoskeleton Substrates

Biological structures have inspired synthetic materials with unparalleled performances such as ultra-lightweight design, tunable elasticity, camouflaging, and antifouling. Among biological structures, exoskeletal scales that cover the exterior surfaces of fishes, fur, and many reptiles. These exoskeletal scales had appeared in the earliest stages of evolution of complex multicellular life and continued their existence in spite of millions of years of evolutionary pressures. This makes them an attractive candidate for biomimicry to produce high performance multifunctional materials with applications to soft robotics, wearables, energy efficient smart skins, antifouling surfaces and on-demand tunable materials. Canonically speaking, biomimetic samples can be fabricated by partially embedding stiffer plate-like segments on softer substrates to create a bi-material system, with overlapping scales. The bending behavior of this system has been carried out using assumption of periodic engagement even after scales contact. This is true only under the most ideal loading conditions or if the scales are extremely dense akin to a continuum assumption on the scales. Here, we develop a rigorous theory with computational validation of key parameters which relaxes these restrictions. We also present an analytical study to demonstrate a bioinspired mechanical pathway to tailor the elasticity of cantilevered beams as an alternative to traditional functional gradation. In addition, we explore for the first time the dynamic behavior of these scales during oscillatory motion using analytical models, supported by finite element (FE) computations. Finally, inspired by the hypothesis that fur surfaces, which consist of plate-like topography, significantly change the initial stages of biofouling, we shed light on the fundamentals of this process by reducing the fur to a scale-covered elastica under flow with biomass suspensions. A FE coupled nonlinear deposition-large deflection model of the system is developed