Geometric mechanics of folded kirigami structures with tunable bandgap. (November 2021)

• Record Type: Journal Article
• Authors: Li, Yanbin; Song, Xiaolei; Liu, Haijun; Yin, Jie
• Is Part Of: Extreme mechanics letters. Volume 49(2021)
• Publication Date: 2021-11
• Subjects: Kirigami structures -- Foldable hinges -- Structural polarization -- Stiffness singularity -- Tunable phononic bandgap; Mechanics -- Periodicals; Mechanics, Applied -- Periodicals; Mechanics; Electronic journals; Periodicals; 531.05
• DOI: 10.1016/j.eml.2021.101483
• Languages: English
• ISSNs: 2352-4316

Abstract

Abstract: We study the geometric mechanics and tunable band structures of a recently developed new class of folded kirigami structures through experiments, theoretical modeling, and numerical simulation. The folded kirigami structures with square and triangular cut patterns are constructed by replacing the point hinge in conventional kirigami sheets with a 3D folding hinge. We find that the folded design can effectively overcome the polarization constraint in the conventional kirigami sheets without folds. Specially, as the creases continue to fold from 0° to 180°, the folded design achieves a unique polarization switch, i.e., the structure expands first and then shrinks to be even smaller than that before folding. Geometric mechanics models are developed to predict how the geometry of the folding hinges determines both the shape changes and structural responses, including nominal strains, polarization switch, Poisson's ratio, folding rate, surface porosity, and structural stiffness. The models are validated through related experiments. We find that the observed polarization switch corresponds to both the peak nominal strains and stiffness singularity in the structures. Lastly, we numerically explore its shape change induced tunable phononic bandgap structures. We find that for special designs with polarization switch, it leads to symmetric bandgap structures changing with the folding angle. This work could find potential applications in designing kirigami metamaterials, shape-morphing materials, and phononic materials with tunable band structures.