Experimentally program large magnitude of Poisson's ratio in additively manufactured mechanical metamaterials

Triangle and honeycomb mechanical metamaterials possess exclusive characteristic of programmable Poisson's ratio. Up to now, the Poisson's ratio of these metamaterials in reported experiments is only within the range of [-4, 1], which is far narrow than the theoretical prediction. In this work, triangle and honeycomb metamaterials were exclusively designed and were fabricated by additive manufacturing. The large magnitude of Poisson's ratios including both positive and negative values was obtained in experimental measurements. Theoretical analysis and numerical simulation were also performed and discussed with the experiments. The results reveal that, under large loading strain, the metamaterials suffer plastic and large deformation, making their Poisson's ratios show significant loading strain dependence. Below the critical loading strain, the metamaterials generate elastic deformation, and the experimentally measured Poisson's ratios agree well with the theoretical perditions and numerical calculation. The as-fabricated triangle and honeycomb metamaterials present programmable positive Poisson's ratio in the ranges of [0.75, 10.92] and [2.80, 13.79], respectively. Besides, the reentrant triangle and honeycomb metamaterials show programmable negative Poisson's ratio in the ranges of [-0.87, -7.01] and [-2.13, -10.24], respectively. These experimentally obtained ranges of Poisson's ratios are far larger than the literature reported experimental results, and provide experimental basis of these mechanical metamaterials to the applications in such as aerospace, civil and transportation.