Origami-inspired deployable auxetic metamaterials

Developing complex spatial objects from a flat sheet of material using origami folding techniques has long attracted attention in science and engineering. Recent research has shown that in origami-based deployable folded sheet materials, such as Miura-ori, metamaterial properties of the patterns are basically because of their folding geometry [1, 2]. In this study, we employ tailored origami folding techniques as a means to create a class of metamaterials. Simple stretching and bending experiments show that these materials exhibit a negative in-plane Poisson’s ratio under extension (i.e., auxetic materials), and a positive Poisson’s ratio under bending. Therefore, similarly to the Miura-ori pattern, the in-plane and out-of-plane Poisson’s ratios of these patterns are of opposite signs, which is an unusual property of such material systems. In-plane Poisson’s ratio and planar stretching -stiffness of such class of materials are also studied analytically. Eigenvalue analysis of the patterns and simple experiments show that these patterns are rigid-foldable, flat-foldable, and have only one kinematic degree of freedom. These properties make them appropriate for applications such as deployable architectural ceiling and façades. In addition, they have the potential to be applied as light cellular folded core material among several other possible engineering applications. REFERENCES [1] Schenk, M. and Guest, S. Geometry of miura-folded metamaterials. Proc. Natl. Acad. Sci. U.S.A. 2013, 110, 3276. [2] Wei, Z., Guo, Z., Dudte, L., Liang, H., Mahadevan, L. Geometric mechanics of periodic pleated origami. Phys. Rev. Lett. 2013, 110, 215501

Origami-inspired structures and materials: analysis and metamaterial properties and seismic design of hybrid masonry structural systems

This dissertation includes two major sections. The first section presents the research on creating and studying novel classes of origami-inspired metamaterials and structures. The second section deals with seismic design of hybrid masonry structural systems. 1) Origami-Inspired Structures and Materials Origami, the traditional Japanese art of paper folding, has been recognized to be a significant source of inspiration in science and engineering. Specifically, its principles have been used for innovative design of mechanical metamaterials for which material properties arise from their geometry and structural layout. Most research on origami-inspired materials relies on known patterns, especially on the Miura-ori, i.e., a classic origami pattern with outstanding properties and a wide range of applications. Motivated by outstanding properties and a broad range of applications of the Miura-ori, in this dissertation, inspired by the kinematics of a one-degree of freedom zigzag strip, we create a novel class of cellular folded sheet mechanical metamaterials. The class of the patterns combines origami folding techniques with kirigami cutting. Using both analytical and numerical models, we study the key mechanical properties of the folded materials. We show that they possess properties as remarkable as those of the Miura-ori on which there has been a surge of research interest. Consequently, the introduced patterns are single degree of freedom (DOF), developable, rigid-foldable and flat-foldable. Furthermore, we show that depending on the geometry, these materials exhibit both negative and positive in-plane Poisson’s ratio. By introducing a novel class of zigzag-base materials, the current study extends the properties of the Miura-ori to those of the class of one-DOF zigzag-base patterns, and our work shows that Miura-ori is only one pattern in this class with such properties. Hence, by expanding upon the design space of the Miura-ori, our patterns are appropriate for a wide range of applications, from mechanical metamaterials to light cellular foldcore sandwich panels and deployable structures at both small and large scales. Furthermore, this study unifies the concept of the in-plane Poisson’s ratio from the literature for similar materials and extends it to this novel class of zigzag-base folded sheet metamaterials. Moreover, in this dissertation, by dislocating the zigzag strips of a Miura-ori pattern along the joining ridges, we create a class of one-degree of freedom (DOF) cellular mechanical metamaterials. We further show that dislocating zigzag strips of the Miura-ori along the joining ridges, preserves and/or tunes the outstanding properties of the Miura-ori. The introduced materials are lighter than their corresponding Miura-ori patterns due to the presence of holes in the patterns. They are also amenable to similar modifications available for Miura-ori which make them appropriate for a wide range of applications across the length scales. Additionally, we study the Eggbox pattern. Similarly to Miura-ori, a regular Eggbox folded sheet includes parallelogram facets which are connected along fold lines. However, Eggbox sheets cannot be folded from a flat sheet of material, and contrary to Miura-ori which has received considerable interest in the literature, there are fewer studies available on Eggbox folded sheet material. By employing both analytical and numerical models, we review and study the key in-plane mechanical properties of the Eggbox folded sheet, and we present cellular folded metamaterials containing Miura-ori and Eggbox cells. The entire structure of the folded materials is a one-DOF mechanism system and, similarly to Eggbox sheets, the materials composed of layers of Eggbox folded sheets are bi-directionally flat-foldable, resulting in a material flexible in those directions, but stiff in the third direction. 2) Seismic Design of Hybrid Masonry Structural Systems Hybrid masonry is an innovative seismic lateral-load resisting system. The system comprises reinforced masonry panels within a steel-framed structure as well as steel connector plates which attach the surrounding steel frame to the masonry panel. Depending on the interfacial conditions between a masonry panel and the steel frame, the system is categorized into three major groups: Types I, II and III. The first part of the research on hybrid masonry systems, in this dissertation, includes a series of exploratory studies aimed at understanding the global behavior of various types of hybrid masonry panels and setting the stage for the study on seismic design of the systems. In this regard, computational analyses were carried out to study the distribution of lateral forces between a masonry panel and a frame in various types of hybrid masonry structural systems. The results are used to demonstrate differences in lateral-force distributions in hybrid masonry systems with different boundary conditions and with various panel aspect ratios as well as with different stiffness of the wall to that of the frame. Furthermore, this study presents the general methodology for seismic design of Type I hybrid masonry systems as well as the steps of a capacity design process in which two favorable ductile modes of behavior are considered: steel connector plates behaving as fuses or flexural yielding of the masonry panels. Moreover, using the proposed approaches we design several prototype buildings located in a high seismic region and investigate viability of hybrid masonry as a new seismic lateral-load resisting system. According to this design framework and the exploratory studies, both approaches are shown to be feasible for developing realistic system configurations. Finally, in this study, an integrated approach for performance-based seismic analysis and design of hybrid masonry Type I systems with fuse connector plates is presented. The procedure used in this study is based on the Capacity Spectrum Method. The proposed method includes an iterative process through which a hybrid masonry structural system with fuse connector plates is designed depending on its energy dissipation capacity. In this regard, the value of the system R factor is regulated in the process. In this study, application of the method for design of a sample hybrid masonry building system is presented

Origami-based cellular metamaterial with auxetic, bistable, and self-locking properties

We present a novel cellular metamaterial constructed from Origami building blocks based on Miura-ori fold. The proposed cellular metamaterial exhibits unusual properties some of which stemming from the inherent properties of its Origami building blocks, and others manifesting due to its unique geometrical construction and architecture. These properties include foldability with two fully-folded configurations, auxeticity (i.e., negative Poisson’s ratio), bistability, and self-locking of Origami building blocks to construct load-bearing cellular metamaterials. The kinematics and force response of the cellular metamaterial during folding were studied to investigate the underlying mechanisms resulting in its unique properties using analytical modeling and experiments