Revealing the co-action of viscous and multistability hysteresis in an adhesive, nominally flat punch: A combined numerical and experimental study

TL;DR

This study investigates how viscous and multistability hysteresis mechanisms jointly influence contact behavior in elastomer-adhesive systems through combined numerical simulations and experiments, revealing enhanced hysteresis effects.

Contribution

It demonstrates the concurrent influence of viscoelasticity and elastic multistability on hysteresis in adhesive contacts, extending existing models and imaging techniques.

Findings

Hysteresis is significantly increased when saddle points contact occurs.

Viscoelastic forces impede contact at saddle points, requiring higher preload.

The coaction of viscous and multistability effects is relevant for polymer contacts and adhesives.

Abstract

Viscoelasticity is well known to cause significant hysteresis of crack closure and opening when an elastomer is brought in and out of contact with a flat, rigid, adhesive counterface. A separate origin of adhesive hysteresis is small-scale, elastic multistability. Here, we study a system in which both mechanisms act concurrently. Specifically, we compare the simulated and experimentally measured time evolution of the interfacial force and the real contact area between a soft elastomer and a rigid, flat punch, to which small-scale, single-sinusoidal roughness is added. To this end, we further the Green's function molecular dynamics method and extend recently developed imaging techniques to elucidate the rate- and preload-dependence of the pull-off process. Our results reveal that hysteresis is much enhanced when the saddle points of the topography come into contact, which, however, is impeded by viscoelastic forces and may require sufficiently large preloads. A similar coaction of viscous- and multistability effects is expected to occur in macroscopic polymer contacts and to be relevant, e.g., for pressure-sensitive adhesives and modern adhesive gripping devices.