Characterization of creases in polymers for adaptive origami engineering

Date of Award

2014

Degree Name

M.S. in Materials Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Advisor: Donald A. Klosterman

Abstract

Origami, the Japanese art of paper folding, has seen a recent shift from a traditional art form to a platform for design of structures capable of actuation. These structures are capable of reconfiguration into multiple defined geometric states by rotation about pre-defined lines in a grid. Thus far, research in the origami field has focused in two broad categories: mathematics and materials. Mathematicians and physicists strive to answer geometry-constrained design questions while material scientists have achieved folding by manipulating material chemistry or geometry. However, studies on crease development through full material thickness have not been conducted in detail (aside from paper and cardboard) with a comprehensive examination of material-dependent fold performance. Material selection guidelines for origami engineering applications can be developed based on numerous fold performance metrics including a thorough understanding of precise failure mechanisms in response to creasing. To characterize crease formation, morphology, permanency, and their relation to fold performance in polymer films, folding and creasing were conducted with a modified parallel plate bending technique. Successful modeling of this technique was achieved for the elastic regime of deformation by applying Euler beam theory. Resulting plastic deformation modes and surface morphology were examined via SEM micrographs revealing tensile deformations ranging from crazing to shear yielding in tension on exterior fold surfaces while compressive deformations such as wrinkling occurred on interior fold surfaces. Wrinkle topology was measured via profilometry revealing a correlation between wrinkle height and tight residual fold angle retention; defined as the fold angle recovery tracked after creasing to provide a quantitative means of comparing fold angle retention and material response to creasing. Modeling residual fold angles based on crease width and material geometry using beam theory incorporating both elastic and plastic deformation in the absence of viscoelastic relaxation effects showed good agreement with experimental data. Retention of smaller fold angles was noted in materials experiencing larger dissipative (crazing, wrinkling, etc.) vs. restorative (elastic) deformation; a result that is favorable or unfavorable depending on the application. Results presented here provide a means of characterizing fold angle retention, one of many fold performance metrics, to establish a classification hierarchy of materials based on potential usefulness in origami engineering applications.

Keywords

Folds (Form), Polymers Mechanical properties, Polymers Testing, Structural control (Engineering), Failure analysis (Engineering), Materials Science, Polymers, origami, bend, crease, fold angle retention, polymer failure mechanisms

Rights Statement

Copyright © 2014, author

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