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

TL;DR

This paper analyzes the delamination behavior of adhesive sheets under uniaxial compression, revealing how confinement, extensibility, and bendability influence the shape and threshold of delamination through energetic and bifurcation analysis.

Contribution

It introduces a scaling framework and a bifurcation model that predict delamination shapes and thresholds based on sheet properties and confinement levels.

Findings

Delamination threshold depends on confinement, extensibility, and bendability.

High bendability leads to large-slope fold delamination.

Lower bendability results in small-slope ruck delamination.

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.