Material-Geometry Interplay in Damping of Biomimetic Scale Beams

Biomimetic scale-covered substrates are architected meta-structures exhibiting fascinating emergent nonlinearities via the geometry of collective scales contacts. In spite of much progress in understanding their elastic nonlinearity, their dissipative behavior arising from scales sliding is relatively uninvestigated in the dynamic regime. Recently discovered is the phenomena of viscous emergence, where dry Coulomb friction between scales can lead to apparent viscous damping behavior of the overall multi-material substrate. In contrast to this structural dissipation, material dissipation common in many polymers has never been considered, especially synergestically with geometrical factors. This is addressed here for the first time, where material visco-elasticity is introduced via a simple Kelvin-Voigt model for brevity and clarity. The results contrast the two damping sources in these architectured systems: material viscoelasticity, and geometrical frictional scales contact. It is discovered that although topically similar in effective damping, viscoelsatic damping follows a different damping envelope than dry friction, including starkly different effects on damping symmetry and specific damping capacity.