Mechanics of Reversible Unzipping

TL;DR

This paper models the reversible unzipping of an elastic layer, revealing how microscopic parameters influence macroscopic adhesion behavior and transitions from ductile to brittle responses, with implications for designing bio-inspired adhesion devices.

Contribution

It provides a rigorous continuum model of reversible decohesion, capturing stable and metastable states, and analyzes the transition from ductile to brittle responses based on microscopic parameters.

Findings

Reproduces abrupt transition from incremental to sudden decohesion.

Shows response varies from quasi-ductile to quasi-brittle with parameter changes.

Provides explicit critical debonding threshold expression.

Abstract

We study the mechanics of a reversible decohesion (unzipping) of an elastic layer subjected to quasi-static end-point loading. At the micro level the system is simulated by an elastic chain of particles interacting with a rigid foundation through breakable springs. Such system can be viewed as prototypical for the description of a wide range of phenomena from peeling of polymeric tapes, to rolling of cells, working of gecko's fibrillar structures and denaturation of DNA. We construct a rigorous continuum limit of the discrete model which captures both stable and metastable configurations and present a detailed parametric study of the interplay between elastic and cohesive interactions. We show that the model reproduces the experimentally observed abrupt transition from an incremental evolution of the adhesion front to a sudden complete decohesion of a macroscopic segment of the adhesion layer. As the microscopic parameters vary the macroscopic response changes from quasi-ductile to quasi-brittle, with corresponding decrease in the size of the adhesion hysteresis. At the micro-scale this corresponds to a transition from a `localized' to a `diffuse' structure of the decohesion front (domain wall). We obtain an explicit expression for the critical debonding threshold in the limit when the internal length scales are much smaller than the size of the system. The achieved parametric control of the microscopic mechanism can be used in the design of new biological inspired adhesion devices and machines.