Abstract
Metastructures consisting of planar arrangements of bi-stable snap-through beams are able to exhibit multiple stable configurations. Apart from the expected translational state transition, when all beam elements snap through, rotational states may exist as well. In this paper we explore the rotational properties of multi-stable metastructures on the basis of both experimental and theoretical investigations, and define the conditions for achieving rotational stable states. Results show that the metastructure is able to realize both translational and rotational states, while the rotational transitions require less energy as compared to their translational counterparts. The influence of geometric parameters on rotational stability is investigated via parametric studies. Furthermore, to determine the design criteria for rotational stability, a theoretical investigation based on mode superposition principle is performed to predict the nonlinear-deformation of a unit cell. The theoretical analysis predicts well the rotational snap-through transitions that are observed in finite element simulations. It is found that the rotational stability is determined by setting proper values for h/L and t/L (h, t, L represent apex height, thickness and span of the bi-stable beam structure, respectively). Finally, we experimentally demonstrate that the proposed metastructure with multiple layers is able to achieve large rotations and translations.
Highlights
The design of mechanical metastructures is a rapidly emerging field, because of the potential to create unusual mechanical properties, such as ultra-high stiffness but lightweight [1,2,3,4,5], negative Poisson’s ratio [6,7,8], and negative thermal expansion [9,10,11,12,13]
In this paper we explore the rotational properties of multi-stable metastructures on the basis of both experimental and theoretical investigations, and define the conditions for achieving rotational stable states
The criterion for reaching rotational states is established through a theoretical investigation
Summary
The design of mechanical metastructures is a rapidly emerging field, because of the potential to create unusual mechanical properties, such as ultra-high stiffness but lightweight [1,2,3,4,5], negative Poisson’s ratio [6,7,8], and negative thermal expansion [9,10,11,12,13] These superior features are mainly realized by the rational design of their unit structures. One way to improve energy efficiency is to introduce bi- or multi-stability, so that a structure maintains different states without the need for continuous energy supply In designing such multi-stable metastructures, pre-shaped beams have been commonly adopted as basic elements since they have large loading-bearing capacity and can be manufactured via additive manufacturing [21,29]. Many examples of regularly assembled pre-shaped beams in one or two dimensions (1D or 2D), referred to as multi-stable beam-type metastructures (MBMs), can be found in literature [31,32,33,34,35,36,37,38,39]
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