Delamination Behavior and Pull-Off Force Analysis of Square Cross-Section Elastomers

Abstract

Achieving high pull-off force in dry adhesive materials often requires a uniform interface stress distribution during delamination. A comprehensive theoretical understanding of delamination behavior, particularly how the interface stress is jointly affected by the interface parameters, material modulus, and width-thickness ratio, is therefore crucial, yet remains lacking. Here, we study the delamination mechanics of square cross-section elastomers, with a focus on their interface stresses and pull-off forces. Two distinct delamination behaviors are exhibited: edge delamination and center delamination. Edge delamination can be further divided into two elastic-stability patterns, rhombus and finger patterns, with transitions driven by the evolution of stress intensity factor distribution along the interface edge. By introducing two key parameters, the ratio of interface stiffness to material modulus ξ and the width-thickness ratio η, and combining FE analysis, we derive quantitative equations for pull-off forces related to edge and center cracks. Our results show that compared to circular cross-section elastomers, square cross-section elastomers are more likely to transition from center delamination to edge delamination as the edge crack pull-off forces decrease due to high stress concentrations at the corners. Square cross-section elastomers exhibit more sensitive pull-off forces within certain ranges of ξ and η, making them a superior option to circular cross-section elastomers for achieving controlled adhesion. This study fills the theoretical gap and provides new guidance for the square cross-section adhesive materials in practical applications.