Quasi-static crushing response of additive manufactured 3D reentrant circular auxetics with different polymer matrices

In the past decades, auxetic metamaterials have attracted extensive interest due to their excellent mechanical properties. In this study, we proposed a novel three-dimensional (3D) reentrant circular (REC) auxetic metamaterial, and investigated its quasi-static crushing responses through experimental tests and numerical simulations. The 3D REC metamaterials were fabricated by the additive manufactured (AM) technique based on different polymer matrix materials, including polyamide-carbon fiber (PA-CF), polyamide (PA) and polypropylene (PP). The morphological characterizations of strut surfaces were revealed, and the effect of matrix material on the crushing behaviors of the REC specimens was examined. The numerical plateau stress and SEA agree well with the experimental results with a maximum relative error of 14.5%. The results show that the PA-CF- and PA-based specimens exhibit different fracture failures, while the PP-based specimen does not fracture during the crushing process. The initial force peak, plateau stress and specific energy absorption (SEA) of the REC specimens decrease in the order of PA-CF > PA > PP, and the larger relative density leads to larger values. In addition, the PP-based specimen shows the smallest Poisson’s ratio under quasi-static crushing, i.e. the most obvious NPR effect, while the PA-CF-based specimen shows the largest Poisson’s ratio.