Mechanics and design of flexible composite fish armor

Abstract

Inspired by the overlapping scales found on teleost fish, a new composite architecture explores the mechanics of materials to accommodate both flexibility and protection. These biological structures consist of overlapping mineralized plates embedded in a compliant tissue to form a natural flexible armor which protects underlying soft tissue and vital organs. Here, the functional performance of such armors is investigated, in which the composition, spatial arrangement, and morphometry of the scales provide locally tailored functionality. Fabricated macroscale prototypes and finite element based micromechanical models are employed to measure mechanical response to blunt and penetrating indentation loading. Deformation mechanisms of scale bending, scale rotation, tissue shear, and tissue constraint were found to govern the ability of the composite to protect the underlying substrate. These deformation mechanisms, the resistance to deformation, and the resulting energy absorption can all be tailored by structural parameters including architectural arrangement (angle of the scales, degree of scale overlap), composition (volume fraction of the scales), morphometry (aspect ration of the scales), and material properties (tissue modulus and scale modulus). In addition, this network of armor serves to distribute the load of a predatory attack over a large area to mitigate stress concentrations. Mechanical characterization of such layered, segmented structures is fundamental to developing design principles for engineered protective systems and composites.