Mechanical characterization of innovative 3D-printed auxetic (NPR) structures: role of considering anisotropy on accuracy of numerical modeling

Owing to being lightweight and offering excellent properties, the auxetic structures characterized by negative Poisson’s ratio are gaining growing interest from academia and industry. In view of the complex nature of these structures, 3D printing owing to offering shape flexibility is gaining increasing attention as a preferred fabrication process. Each cell in these structures consists of multiple ribs printed with different orientations thereby likely to show mechanical anisotropy when loaded. To accurately model their mechanical behavior and thus to reliably assess their performance through numerical modeling, anisotropy should be taken into account. This subject has been merely addressed in numerical modeling of printed auxetic structures, especially for those fabricated through fused deposition modeling (FDM), a 3D printing technique. The present study, therefore, addresses this subject. The ABS polymer is employed as the experimental material. For numerical modeling, the necessary material constants are determined by following the standard printing and testing practices. A variety of auxetic structures are designed and their mechanical behaviors are studied numerically as well as experimentally. The analysis shows that the anisotropic model yields fairly accurate results comparable to the experimental ones, while the isotropic model suffers from an error of 26%. The presented study is the first of its nature and is believed to act as a guideline for accurately assessing the mechanical performance of auxetic structures.