Negative stiffness structures (NSS), as a branch of multi-stable mechanical metamaterials, exhibit multiple stable configurations. Their characteristics, such as bistability, snap-through and negative stiffness, make them particularly suitable for shock absorber applications. The majority of NSS is designed in a cuboidal shape and only recently few studies focused on cylindrical NSS. Lately, Fraunhofer for Additive Manufacturing Technologies IAPT, has started some studies to optimize these structures and to profit by their features in different applications, such as InspectionCopter project. During this study, three types of special-shaped NSS were designed, produced and tested. To determine the influence of dimensional parameters and materials on the functionality of these flexible structures, for each one of three concepts, five different versions in two different materials and techniques were realized. The specimens were fabricated in PEBA (PolyEther Block Amide) and TPU (Thermoplastic PolyUrethane) using, respectively, Selective Laser Sintering (SLS) and MultiJet Printing (MJP) technologies; the design freedom of Additive Manufacturing (AM) allows the production of complex structures and the possibility of functional integration, such as shock absorber functionality. To investigate the mechanical and NS properties of these structures and their deformation mechanisms, quasi-static compression tests were performed according to ASTM D695 − 15 regulation. The results, analyzed through force–displacement curves, highlighted the energy recovery of the specimens during deformation and the influence of dimensional parameters on the response to the applied loads. During the tests, it was also evident how the usage of different dimensions and materials can lead, for the same structure, to a symmetric or asymmetric buckling mode in the collapse of the layers and to prevent the structure from returning to its original shape once the load has been removed.

负刚度结构（NSS）作为多稳态机械超材料的一个分支，具有多种稳定的构型。它们的特性，例如双稳性，快速断裂和负刚度，使其特别适合于减震器应用。NSS的大多数设计为长方体形状，只有最近很少有研究关注圆柱NSS。最近，IAPT增材制造技术公司的Fraunhofer开始进行一些研究，以优化这些结构并利用它们在不同应用中的功能（例如InspectionCopter项目）获利。在这项研究中，设计，生产和测试了三种类型的异形NSS。对于三个概念中的每一个，要确定尺寸参数和材料对这些柔性结构的功能的影响，实现了两种不同材料和技术的五个不同版本。分别使用选择性激光烧结（SLS）和MultiJet印刷（MJP）技术在PEBA（聚醚嵌段酰胺）和TPU（热塑性聚氨酯）中制造样品；增材制造（AM）的设计自由度允许生产复杂的结构，并可以进行功能集成，例如减震器功能。为了研究这些结构的机械和NS特性及其变形机理，根据ASTM D695-15法规进行了准静态压缩试验。通过力-位移曲线分析的结果强调了试样在变形过程中的能量回收以及尺寸参数对施加载荷响应的影响。