Elastic stabilisation of wrinkles in thin films by auxetic microstructure

TL;DR

This paper investigates how auxetic microstructures in thin elastic films suppress bulk wrinkling under tension, leading to localized edge creases, with analysis supported by experiments, theory, and simulations.

Contribution

It introduces the mechanics of auxetic thin films under tension, revealing suppression of bulk wrinkles and formation of localized edge creases, supported by multi-method analysis.

Findings

Bulk wrinkling is suppressed in auxetic films under tension.

Localized edge creases form and decay exponentially away from clamps.

Scaling laws for amplitude, wavelength, and decay rate are derived.

Abstract

Thin elastic sheets and membranes are known to wrinkle when they are stretched -- the associated physics is highly non-linear. The mechanics of thin films that exhibit unusual behavior upon stretching, when they possess auxetic structure, i.e. when their apparent Poisson's ratio is negative, is presented here. Wrinkling is now suppressed within the bulk of auxetic films when tensioned, whereas localized creases confined to the clamps, that decay away exponentially, appear. These edge wrinkles are characterized for their amplitude and wavelength experimentally, theoretically, and computationally, which show excellent agreement with expected trends. The scaling for amplitude, wavelength and decay rate upon film properties and tension is obtained using simple analyses based on kinematic mismatch resulting from lateral Poisson's expansion.