Rucks and folds: delamination from a flat rigid substrate under uniaxial compression

Abstract

We revisit the delamination of a solid adhesive sheet under uniaxial compression from a flat, rigid substrate. Using energetic considerations and scaling arguments we show that the phenomenology is governed by three dimensionless groups, which characterize the level of confinement imposed on the sheet, as well as its extensibility and bendability. Recognizing that delamination emerges through a subcritical bifurcation from a planar, uniformly compressed state, we predict that the dependence of the threshold confinement level on the extensibility and bendability of the sheet, as well as the delaminated shape at threshold, varies markedly between two asymptotic regimes of these parameters. For sheets whose bendability is sufficiently high the delaminated shape is a large-slope "fold", where the amplitude is proportional to the imposed confinement. In contrast, for lower values of the bendability parameter the delaminated shape is a small-slope "ruck", whose amplitude increases more moderately upon increasing confinement. Realizing that the instability of the fully laminated state requires a finite extensibility of the sheet, we introduce a simple model that allows us to construct a bifurcation diagram that governs the delamination process.

Drop Spreading and Confinement in Swelling-Driven Folding of Thin Films

“…Accordingly, the gap volume under the debonded film is constrained to be zero, and the strain energy can only be released into a self-contacting fold (Figure b). Despite a number of articles showing the type of folding discussed here, − , buckling subject to the no-gap constraint is not well understood. Here, we present a simplified model for the critical swelling ratio, λ c , needed to initiate folds under the no-gap constraint.…”

“…Further compression causes some wrinkles to grow into localized folds while the rest of the film reverts to becoming flat. In contrast, in the case of Figure , folds can arise directly from a flat film, although creasing or telephone-cord delamination is sometimes observed prior to fold growth. , Such fold formation represents a new type of delamination mode that is distinct from the standard modes well known in the thin-film community . If this folding process can be understood and controlled, it offers a simple method for creating high aspect ratio microscale features on a surface.…”

Delamination from an adhesive sphere: Curvature-induced dewetting versus buckling

“…To understand how and when the appearance of compression affects the onset of delamination, we begin by considering the case in which the sheet has very little resistance to bending. In this case, a recent study of the one-dimensional analogue problem [20] suggests that delamination blisters in highly bendable sheets take the form of 'folds': the amplitude A is large in comparison with the width of the blister λ (as shown in fig. 3) and, further, that λ ∼ bc where bc = (B/Γ) 1/2 is the bendocapillary length and B ∝ Et 3 is the bending stiffness of the sheet.…”

How to unloop a self-adherent sheet

“…Folding, self-adhering, blistering, and peeling phenomena occur in many types of thin elastic layers, such as capillary films [1][2][3], soft adhesives [4,5], protective coatings or multi-layered materials [6][7][8], thin films floating on liquid or polymer substrates [9,10], or graphene sheets [11,12]. The mechanical properties and stability of these layers are crucial to applications such as thin flexible electronic devices [10,13], soft robotics [14], the self-assembly of graphene ribbons [15] or liquid-phase exfoliation of layered two-dimensional nanomaterials [16].…”