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Research Papers

Design Tools for Patterned Self-Folding Reconfigurable Structures Based on Programmable Active Laminates

[+] Author and Article Information
Edwin A. Peraza Hernandez

Department of Aerospace Engineering,
Texas A&M University,
College Station, TX 77843-3141
e-mail: eperaza@tamu.edu

Darren J. Hartl

Research Assistant Professor
Department of Aerospace Engineering,
Texas A&M University,
College Station, TX 77843-3141
e-mail: darren.hartl@tamu.edu

Richard J. Malak, Jr.

Assistant Professor
Design Systems Laboratory,
Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77843-3123
e-mail: rmalak@tamu.edu

Ergun Akleman

Professor
Visualization Department,
Texas A&M University,
College Station, TX 77843-3137
e-mail: ergun.akleman@gmail.com

Ozgur Gonen

Department of Architecture,
Texas A&M University,
College Station, TX 77843-3137
e-mail: ozgur.gonen@gmail.com

Han-Wei Kung

Visualization Department,
Texas A&M University,
College Station, TX 77843-3137
e-mail: hanwei@tamu.edu

1Corresponding author.

Manuscript received July 1, 2015; final manuscript received October 24, 2015; published online March 11, 2016. Assoc. Editor: Mary Frecker.

J. Mechanisms Robotics 8(3), 031015 (Mar 11, 2016) (12 pages) Paper No: JMR-15-1176; doi: 10.1115/1.4031955 History: Received July 01, 2015; Revised October 24, 2015

Engineering inspired by origami has the potential to impact several areas in the development of morphing structures and mechanisms. Self-folding capabilities in particular are necessary in situations when it may be impractical to exert external manipulations to produce the desired folds (e.g., as in remote applications such as in space systems). In this work, origami principles are utilized to allow planar sheets to self-fold into complex structures along arbitrary folds (i.e., no hinges or pre-engineered locations of folding). The sheets considered herein are composed of shape memory alloy (SMA)-based laminated composites. SMAs are materials that can change their shape by thermal and/or mechanical stimuli. The generation of sheets that can be folded into the desired structures is done using origami design software such as Tachi's freeform origami. Also, a novel in-house fold pattern design software capable of generating straight and curved fold patterns has been developed. The in-house software generates creased and uncreased fold patterns and converts them into finite element meshes that can be analyzed in finite element analysis (FEA) software considering the thermomechanically coupled constitutive response of the SMA material. Finite element simulations are performed to determine whether by appropriately heating the planar unfolded sheet it is possible to fold it into the desired structure. The results show that a wide range of self-folding structures can be folded via thermal stimulus. This is demonstrated by analyzing the folding response of multiple designs generated from freeform origami and the newly developed in-house origami design software.

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References

Figures

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Fig. 1

(a) Staggered mesh design for the SMA-based self-folding sheet. (b) Experimental prototype of a self-folding sheet showing reference flat configuration and two different “folded” configurations. Note (i) the broad nature of the “folds” in this preliminary prototype and (ii) the reconfigurability of this single prototype.

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Fig. 2

SMA-based self-folding sheet homogeneously heated on its top SMA layer deforms toward a form of limited utility. The contour plot shows martensite volume fraction.

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Fig. 3

SMA-based self-folding sheet heated in a Miura-ori-based pattern deforms in a structured manner, enabling locomotion. The contour plot shows martensite volume fraction.

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Fig. 4

Topologically distinct pattern categories and folded shapes from those patterns. The dashed lines represent valley folds and the dotted lines represent mountain folds. (a) Glide-reflection wallpaper pattern on a rectangular grid. (b) Simple pattern on a quad-pattern coverable domain that demonstrates axial symmetry. (c) Locally consistent wallpaper pattern on a planar two-manifold mesh domain with quadrilateral and triangular faces. Note that the pattern in the center square is different than the rest (the center square requires significant bending of the faces to be folded).

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Fig. 5

Examples of procedures for the creation of quad-heavy meshes: (a) create n × m grid, (b) create toroid, (c) create polygon, and (d) thicken a medial axis

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Fig. 6

Examples of quadrilateral preserving local operations: (a) two-edge split, (b) edges split, (c) extrude faces, (d) insert edge, (e) insert eye, and (f) ring split

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Fig. 7

Examples of meshes with or without QPC property. Shaded regions indicate pattern inconsistency in non-QPC meshes: ((a) and (b)) QPC examples and ((c) and (d)) non-QPC examples.

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Fig. 8

Uniaxial tensile test results of an elastomeric specimen (RTV silicone) used to fabricate self-folding sheets. A linear fit is used to determine the effective Young's modulus of the elastomer for small strains.

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Fig. 9

Process used to import a crease pattern from freeform origami into abaqus finite element software: (a) fold pattern generated by freeform origami imported as a line sketch, (b) rotation, scaling, and positioning of the sketch into a sheet with user-defined dimensions, (c) thickening of folding lines to obtain arbitrarily thick heating regions [39], (d) Mountain and valley fold assignments, and (e) discretization into finite elements for analysis. This process is based on the one previously shown in Ref. [39].

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Fig. 10

Self-folding SMA-based laminate morphing toward a regular Miura-ori model generated by freeform origami. The crease pattern is shown (solid lines indicate mountain folds while dashed lines indicate valley folds). The model in the visualization tool of freeform origami is also shown. Martensite volume fraction contour plot and shaded shape deformation plot from abaqus FEA software at the end of the analysis procedure are presented. The symmetric analysis domain has been mirrored for the sake of visualization.

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Fig. 11

Self-folding SMA-based laminate morphing toward a Miura-ori-based freeform model generated by freeform origami. The crease pattern is shown (solid lines indicate mountain folds while dashed lines indicate valley folds). The model in the visualization tool of freeform origami is also shown. Martensite volume fraction contour plot and shaded shape deformation plot from abaqus FEA software at the end of the analysis procedure are presented. The symmetric analysis domain has been mirrored for the sake of visualization.

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Fig. 12

Self-folding SMA-based laminate morphing toward a regular waterbomb model generated by freeform origami. The crease pattern, the model in the visualization tool of freeform origami, martensite volume fraction contour plot, and shaded shape deformation plot from abaqus FEA software at the end of the analysis procedure are presented.

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Fig. 13

Self-folding SMA-based laminate morphing toward a regular Ron Resch model generated by freeform origami. The crease pattern, the model in the visualization tool of freeform origami, martensite volume fraction contour plot, and shaded shape deformation plot from abaqus FEA software at the end of the analysis procedure are presented.

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Fig. 14

Elliptical annulus geometry and fold pattern example. The folds are already thickened by the in-house software.

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Fig. 15

Main effects plot showing the trends of maximum absolute out-of-plane displacement normalized by semimajor length versus various input parameters for the elliptical annulus

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Fig. 16

(a) Shaded deformed and undeformed configurations for the elliptical annulus with maximum uzmax/a. This annulus corresponds to design 6 in Table 4. (b) Martensite volume fraction contour plots of the annulus. The fold radius of curvature Rf is shown at the location of tightest folds.

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Fig. 17

Fold locations, shaded undeformed and deformed plots, and martensite volume fraction contour plots for the hollow squarelike self-folding sheet. The fold radius of curvature is shown at the location of tightest folds.

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