Torsion-mediated instabilities in confined elastic layers

Abstract

When a soft elastic layer confined between two rigid substrates is subjected to tensile loads, the stressed layer exhibits various modes of elastic instability that influence its mechanical response. While previous studies have primarily focused on analyzing these instabilities under normal tension, this study systematically investigates the impact of combined tension–torsion loading on the emergence of fingering and fringe instabilities. Through a combination of theoretical, experimental, and numerical analysis, we show that the application of torsion can tune the mode of instabilities in elastic layers with moderate aspect ratios. We also demonstrate that torsion controls the monotonicity of the stress–stretch relationship in elastic layers with large aspect ratios. We construct a phase diagram that delineates the mode of instability and the monotonicity of the stress–stretch curve in confined elastic layers as a function of the applied torsion angle and the sample’s aspect ratio. This work not only provides mechanistic insights into the role of torsion in stabilizing the response of confined elastic layers, but also offers a valuable tool for designing soft yet tough adhesive systems capable of withstanding complex mechanical loads.