  Biomimetic scale-covered substrates provide geometric tailorability via scale
orientation, spacing and also interfacial properties of contact in various
deformation modes. No work has investigated the effect of friction in twisting
deformation of biomimetic scale-covered beams. In this work, we investigate the
frictional effects in the biomimetic scale-covered structure by developing an
analytical model verified by the finite element simulations. In this model, we
consider dry (Coulomb) friction between rigid scales surfaces, and the
substrate as the linear elastic rectangular beam. The obtained results show
that the friction has a dual contribution on the system by advancing the
locking mechanism due to change of mechanism from purely kinematic to
interfacial behavior, and stiffening the twist response due to increase the
engagement forces. We also discovered, by increasing the coefficient of
friction using engineering scale surfaces to a critical coefficient, the system
could reach to an instantaneous post-engagement locking. The developed model
outlines analytical relationships between geometry, deformation, frictional
force and kinematic energy, to design biomimetic scale-covered metamaterials
for a wide range of application.
