Toughening and asymmetry in peeling of heterogeneous adhesives

TL;DR

This study combines experiments and theory to understand how microscale heterogeneities in adhesives influence macroscale peeling behavior, revealing mechanisms for enhanced resistance and asymmetry in adhesive systems.

Contribution

It introduces a multiscale approach showing how microscale variations affect macroscale peeling, enabling design of adhesives with tailored properties.

Findings

Patterning elastic stiffness enhances peeling resistance.

Optimized pinning sites control adhesion and anisotropy.

Heterogeneities cause front instabilities and energy releases.

Abstract

The effective adhesive properties of heterogeneous thin films are characterized through a combined experimental and theoretical investigation. By bridging scales, we show how variations of elastic or adhesive properties at the microscale can significantly affect the effective peeling behavior of the adhesive at the macroscale. Our study reveals three elementary mechanisms in heterogeneous systems involving front propagation: (i) patterning the elastic bending stiffness of the film produces fluctuations of the driving force resulting in dramatically enhanced resistance to peeling; (ii) optimized arrangements of pinning sites with large adhesion energy are shown to control the effective system resistance, allowing the design of highly anisotropic and asymmetric adhesives; (iii) heterogeneities of both types result in front motion instabilities producing sudden energy releases that increase the overall adhesion energy. These findings open potentially new avenues for the design of thin films with improved adhesion properties, and motivate new investigation of other phenomena involving front propagation.