A negative stiffness structure with multi-stable characteristic

This work proposes a straw-shaped structure (SS) inspired by the folds of straw. Two samples named SSⅠ and SSⅡ with 5 and 5.5 layers of conical structures, respectively, are prepared using selective laser sintering (SLS) technology. SSⅠ and SSⅡ can spontaneously recover to their original shapes after compression experiments. With the thickness of 0.6 and 3.0 mm for the upper and lower parts of cells, the peak and valley forces of SSII (SS-3.0-0.6) during compression and tension alternate periodically. The first and second valley forces of SS-3.0-0.6 are −16.1 and −20.2 N during compression, and its second, fifth and fourth peak forces are 30.2, 4.3 and 0.8 N during tension. SS-3.0-0.6 exhibits significant NS and multi-stable properties in both compression and tension, and it is easier to be stretched than compressed. The deformation mode of the folded structure is similar to stacked porcelain bowls. Through a reasonable design of geometric parameters, the folding order and deformation mode as well as the number of stable state of the SSII models can be customized. In addition, the potential applications of SSs are also discussed, and this work provides a valuable reference for the study of NS structures.