Effect of beam configuration on its multistable and negative stiffness properties

Multistable and negative stiffness mechanical metamaterials are promising and gain great attention recently. Beam structure is the most commonly used negative stiffness element in these metamaterials’ designs. The tilted beam element (V-shape) and the curved beam element are frequently exploited, but their difference is almost neglected. In this study, we investigated the mechanical properties of the beam structures with different configurations (the tilted, the curved, and the arched shapes) and the influence of the variable cross-section design using a combination of analytical, numerical and experimental methods. We draw the geometric parameter boundary of positive stiffness, negative stiffness, and bi-stable regions for these beam structures, and compare their basic mechanical properties as well as energy trapping capacity. Research results indicate that the curved beam and the tilted beam respectively show better performance in different parameter regions, and are both more suitable than the arched beam in constructing the metamaterials. The variable cross-section design can be applied to tune the basic mechanical properties and shift the boundary for various mechanical behaviors. The obtained results are also verified in different material systems and can be a reference to the design of multistable and negative stiffness mechanical metamaterials.