Thin films usually exhibit instabilities and yield intricate wrinkles when two clamped ends are twisted. Here, we explore the wrinkling behavior and pitch-fork bifurcation of twisted thin films experimentally and theoretically. To quantitatively predict the post-buckling evolution of twist-induced wrinkling morphology, we develop a refined finite-strain plate model derived from 3D field equations and then solve it by using the finite element method with COMSOL. We examine the effects of aspect ratios and pre-tension on the wrinkling profile.
Dear iMechanicians, I would like to share our recent work on the poking and bulging of elastic thin sheets that were inspired by the classical indentation test and bulge test. Under clamped boundaries, there have been well-established theories and well-controlled experiments in this field.
Transverse wrinkles commonly occur in a uniaxially tensile elastic membrane and can vanish upon excess stretching. The wrinkling direction is usually perpendicular to the stretching direction under isotropic elasticity. Here, we show that wrinkles are orientable by material anisotropy, such as in fiber-reinforced or fibrous films, and the wrinkling orientation can be tuned by varying the stiffness and direction of fibers.
Self-positioned nanomembranes such as rolled-up tubes and wrinkled thin films have been potential systems for a variety of applications and basic studies on elastic properties of nanometer-thick systems. Although there is a clear driving force towards elastic energy minimization in each system, the exploration of intermediate states where specific characteristics could be chosen by a slight modification of a processing parameter had not been experimentally realized.
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