Design and macroscopic mechanical responses of auxetic metamaterials with tunable stiffness

This research presents the design, manufacturing, and macroscopic characterization of flexible mechanical metamaterials with tunable elastic properties. The elastic constants were given using the energy principle and Castigliano's second theorem, and the results were validated through static simulations and tensile experiments, showing good agreement. Then the complete parametric study was conducted to demonstrate the possibility of extensively customizing the Poisson effect and stiffness. Additionally, the comparison between the developed metamaterials and star-shaped cellular structures on the mechanical properties was conducted using six groups of samples. The results demonstrated that the developed metamaterials exhibited remarkable superiority in deformability, sensitivity, and auxeticity. Furthermore, an innovative experiment is devised to characterize the mechanical responses of the developed coupling metamaterials system complemented with numerical modeling, the similar phenomenon was also observed in other metamaterials. The proposed design offered a way to induce the metamaterials system's profile occurring the wavy deformation.