Stress and Fold Localization in Thin Elastic Membranes

Abstract

Thin elastic membranes supported on a much softer elastic solid or a fluid deviate from their flat geometries upon compression. We demonstrate that periodic wrinkling is only one possible solution for such strained membranes. Folds, which involve highly localized curvature, appear whenever the membrane is compressed beyond a third of its initial wrinkle wavelength. Eventually the surface transforms into a symmetry-broken state with flat regions of membrane coexisting with locally folded points, reminiscent of a crumpled, unsupported membrane. We provide general scaling laws for the wrinkled and folded states and proved the transition with numerical and experimental supported membranes. Our work provides insight into the interfacial stability of such diverse systems as biological membranes such as lung surfactant and nanoparticle thin films.

Localization of Folds and Cracks in Thin Metal Films Coated on Flexible Elastomer Foams

“…Larger applied strain forces these wrinkles merge into a single fold (Figure 1 d), while the surrounding gold fi lm is intact. [15][16][17] Sub-millimeter thick membranes of PU foam are produced using a simple bar coater setup ( Figure 2 a). A variety of two-component systems are available to produce PU foams, allowing for a wide range of foam densities and morphologies.…”

The role of substrate pre-stretch in post-wrinkling bifurcations

“…For a thin elastic film supported on a viscous substrate, wrinkles lose their periodicity and transition to localized folds once the total confinement of the thin film approaches one third of the initial wrinkling wavelength [33,34] . The transition to localized deformation may even lead to the fracture of the film [35] .…”

Swelling-Induced Folding in Confined Nanoscale Responsive Polymer Gels

“…44Ϫ48 It has been demonstrated that buckling and folding are not independent phenomena and wrinkles appear as a first order linear response to external or internal stresses. 49 Folding and crumpling of compliant structures result in localization of the strain energy into a network of ridges and sharp corners. 50Ϫ52 Herein, we report ultrathin (20Ϫ100 nm) gel films tethered to solid substrates which exhibit unusual spontaneous and regular self-folding under swelling induced compressive stresses.…”