Surface Instability in Soft Materials

Surface Instability in Soft MaterialsRui HuangUniversity of Texas at AustinOutlineElastomer (rubber) block

Elastomer bilayer (thin film) or graded stiffness

Polymer gels

Electromechanical instability of dielectric elastomer

A simple buckling problem Elastomer blockWrinkling or creasing?Biots linear perturbation analysis for wrinklingNonlinear stability analysis for creasing (Hohlfeld and Mahadevan, 2011; Hong et al., 2009)From wrinkles to creases (Cao and Hutchinson, PRSA 2012)Effect of surface energy (Chen et al., 2012)

From instantaneous to setback creasesDiab, Zhang, Zhao, Gao and Kim (2013)

Elastic bilayers: from wrinkling to folding

Cao and Hutchinson, JAM 2012Effect of pre-stretched substrates

Cao and Hutchinson, JAM 2012Experiments

Sun et al., 2012

Pocivavsek et al., 2008More bifurcations

Brau et al., 2010Gels: Swell-Induced InstabilityTrujillo et al, 2008.

Tanaka et al, 1987

Wrinkles or creases?Critical conditionCharacteristic sizeEffect of kineticsAbundant experimental observations, but lacking fundamental understanding.

Bilayer gels: two types of instability

ABWu, Bouklas and Huang, IJSS 50, 578-587 (2013).Type A: soft-on-hard bilayer, critical condition at the short wave limit, forming surface creases;

Type B: hard-on-soft bilayer, critical condition at a finite wavelength, forming surface wrinkles first (and then creases).10

Gradient and kinetics

Guvendiren et al, 2009 & 2010.Other geometries

Wu et al, 2013.

Dervaux et al, 2011.

DuPont et al, 2010.Dielectric elastomer membranes: Electromechanical instability

Plante and Dubowsky, IJSS 2006.

Huang and Suo, 2012.A simple buckling problem?simply supported, but allow vertical displacementxyAt x = 0, buckling amplitude is zero (no buckling)At x infinity, unconstrained buckling (long wavelength mode)In between, short-wavelength mode appears near the end, and transition of buckling mode occurs.Postbuckling behavior: how would the buckling mode change with position (x) and the compressive strain?From graphene to curtain: Wrinklons?

Vandeparre et al., 2011.