Experimental Investigation of Mechanical Behavior in Auxetic Metamaterials Manufactured by FDM Using PLA and PETG

Additive manufacturing (AM) has expanded the development of structures with high ge-ometric complexity and tunable mechanical behavior, particularly in mechanical met-amaterials. This study evaluates the mechanical performance of cellular structures pro-duced by fused deposition modeling (FDM) using polylactic acid (PLA) and polyethylene terephthalate glycol (PETG), considering standard specimens and three cellular architec-tures: conventional honeycomb, reentrant honeycomb, and EigenModes. The specimens were subjected to tensile, flexural, and compressive tests. PLA exhibited higher mechanical resistance in the standard specimens, reaching 1008 N in tensile loading, 41 N in flexural loading, and 99,150 N in compression. PETG showed lower maximum force values in most standard configurations but demonstrated better performance in selected cellular architectures. In the reentrant honeycomb geometry under compression, PETG reached 9,075 N, outperforming PLA by approximately 173%. This result indicates that ductility becomes decisive when the architecture activates deformation mechanisms typical of aux-etic mechanical metamaterials, such as inward folding, rib rotation, and cell-wall bending. Scanning electron microscopy (SEM) confirmed distinct fracture features, with PLA showing predominantly brittle fracture and interlayer separation, while PETG showed greater tolerance to voids and localized deformation. Overall, the results demonstrate that the mechanical response of FDM-printed metamaterials is governed by the interaction be-tween material behavior and cellular topology, rather than by polymer properties alone.