Mechanical Engineering ETDs

Publication Date

Summer 7-29-2025

Abstract

When a thin film bonded to a thick compliant substrate is subject to in-plane compression, wrinkles can develop if the critical state for instability is reached. In various applications the film/substrate system may also take the form of cylindrical fibers, where an axial compressive loading can trigger axisymmetric wrinkles. A straightforward computational approach to simulate such wrinkling behavior is needed for material design, to either prevent wrinkling or to exploit its benefits for flexible device applications. In this work a comprehensive numerical study is undertaken by employing the finite element method. The embedded imperfection approach used previously for planar structures is now applied to the cylindrical film/substrate system to trigger axisymmetric wrinkles. Uniform and reversible elastic wrinkles can be directly predicted, and the wrinkle geometries are verified by available elastic analytical solutions. The effect of initial imperfection location is also examined. We further study plastic yielding and viscoelasticity of the thin film and examine how the wrinkle configuration may be influenced by inelastic deformation. Yielding transforms the uniform wrinkles into localized deep folds, and this new surface feature is irrecoverable upon unloading. A viscoelastic thin film results in rate-dependent instability behavior, with very slow strain rates favoring localized waveforms.

Keywords

Wrinkle, instability, thin film, deformation, yielding

Degree Name

Mechanical Engineering

Level of Degree

Masters

Department Name

Mechanical Engineering

First Committee Member (Chair)

Dr. Yu-Lin Shen

Second Committee Member

Dr. Heng E. Zuo

Third Committee Member

Dr. Donghyeon Ryu

Sponsors

NASA EPSCoR CAN (grant #: 80NSSC23M0069)

Document Type

Thesis

Language

English

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