The effects of printing directions on the compression behavior of the Re-entrant structure produced by 3D printing technology

In this work, a re-entrant structure having a negative Poisson’s ratio (NPRs) was designed and produced with polylactic acid (PLA) using 3D printing technology. A series of samples was prepared with the different printing directions, namely, printed following (PF) the structure orientation, at 0[Formula: see text] (PZ) and at 90[Formula: see text] (PN). Results showed that the printing direction plays a crucial role in determining the mechanical properties of the printed meta-materials. In particular, PF specimens achieved the highest energy absorption at break, which is [Formula: see text]2 times as high as PZ or PN samples. The PF specimens also showed the highest stiffness under compression. However, the Poisson’s ratio was less sensitive to the changes in printing directions. The measured Poisson’s ratios for PF, PZ and PN samples are −1.68, −1.87 and −1.70, respectively. Based on the experimental results, the effects of the printing direction and the geometry configuration of the structure on the deformation behavior of the printed meta-material were further discussed.