Super Elasticity of Polymeric Thermoplastic Metamaterial with Antichiral Design

The room-temperature deformation and fracture processes in polymeric (PLA and PA12) samples with an antichiral interior design have been studied through computer simulation and experimental research. The samples were printed by two different methods: FDM and SLS. ANSYS software was utilized to simulate the compression deformation process. The simulation showed that the Poisson ratio of the studied 3D model samples did not depend on the chemical composition and was close to zero under compression. It was found that under the same load, the von Mises stresses in the polylactic acid (PLA) sample were almost twice as high as in the polyamide 12 (PA12) sample structure, which was associated with the different mechanical properties of the initial material. Maximum von Mises stresses were observed in the cylindrical region of the bottom part of the sample. The room-temperature compression experiments revealed that the deformation process of the samples with the antichiral design occurs layer by layer. Room-temperature superelasticity effects associated with both viscoelastic relaxation of the cellular antichiral design and phase transition were found in the 3D-printed PA12 thermoplastic polymeric sample; the sample was deformed up to 49% and recovered its shape after removing the load. The recovery coefficient (Rr) for the PA12 sample was 99 ± 1%. The shape-memory effect in the 3D-printed PLA sample was found when it was immersed in hot water at a temperature of 80 °C. Because the 3D-printed PLA sample was partially destroyed under compressive deformation, the recovery coefficient of the PLA sample for the temperature-induced shape-memory effect was 86%. The microscopy study (SEM) revealed the limitations of the FDM method for printing 3D objects with complex designs, such as antichiral ones. Unlike the SLS method, FDM printing does not provide a strong connection between the cylindrical and ligament parts of the antichiral design structure due to the fibril structure of the PLA filaments and the printing strategy used in FDM.