A novel cylindrical mechanical metamaterial: Design, fabrication, and compressive properties

Mechanical metamaterials exhibit fascinating deformation characteristics and exceptional mechanical properties due to their distinctive unit cell structure and the repetitive development of these units. This research presents the design of a novel cylindrical metamaterial featuring a concave hexagonal structure. This design incorporates an auxetic structure within the outer circular tube in order to enhance radial shrinkage and improve bearing capacity and stability by leveraging the negative Poisson's ratio effect. The specimens were fabricated using 3D printing technology, and their mechanical properties and uniaxial compression deformation characteristics were subsequently investigated through experiments. Additionally, the accuracy of the finite element model was verified by comparing the simulated predictions with the experimental results. The specimens differ in terms of their internal and external structures. The external structures vary based on the combination of single cells and interlayers, resulting in three distinct types. The internal structures differ based on the angle of inward depression. The mechanical properties and deformation characteristics of specimens composed of different internal and external structures were analyzed, revealing that the cylindrical structure can possess adjustable stiffness, high stability, and compressive capacity.