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Surface Instability in Soft M aterials

Surface Instability in Soft M aterials. Rui Huang University of Texas at Austin. O utline. Elastomer (rubber) block Elastomer bilayer (thin film) or graded stiffness Polymer gels Electromechanical instability of dielectric elastomer A simple buckling problem . Elastomer block.

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Surface Instability in Soft M aterials

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  1. Surface Instability in Soft Materials Rui Huang University of Texas at Austin

  2. Outline • Elastomer (rubber) block • Elastomer bilayer (thin film) or graded stiffness • Polymer gels • Electromechanical instability of dielectric elastomer • A simple buckling problem

  3. Elastomer block • Wrinkling or creasing? • Biot’s linear perturbation analysis for wrinkling • Nonlinear 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)

  4. From instantaneous to setback creases Diab, Zhang, Zhao, Gao and Kim (2013)

  5. Elastic bilayers: from wrinkling to folding Cao and Hutchinson, JAM 2012

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

  7. Experiments Sun et al., 2012 Pocivavsek et al., 2008

  8. More bifurcations Brau et al., 2010

  9. Gels: Swell-Induced Instability • Wrinkles or creases? • Critical condition • Characteristic size • Effect of kinetics Tanaka et al, 1987 Abundant experimental observations, but lacking fundamental understanding. Trujillo et al, 2008.

  10. Bilayer gels: two types of instability A B • 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). Wu, Bouklas and Huang, IJSS 50, 578-587 (2013).

  11. Gradient and kinetics Guvendirenet al, 2009 & 2010.

  12. Other geometries Wu et al, 2013. Dervauxet al, 2011. DuPont et al, 2010.

  13. Dielectric elastomer membranes: Electromechanical instability Plante and Dubowsky, IJSS 2006. Huang and Suo, 2012.

  14. A simple buckling problem? simply supported, but allow vertical displacement y x • At 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?

  15. From graphene to curtain: Wrinklons? Vandeparre et al., 2011.

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