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

Additive manufacturing enables the fabrication of cellular structures with complex geometries and tunable mechanical response. This study evaluates auxetic-inspired cellular metamaterials manufactured by fused deposition modeling using polylactic acid (PLA) and polyethylene terephthalate glycol (PETG). Standard specimens and three cellular architectures, namely conventional honeycomb, re-entrant honeycomb, and EigenModes, were investigated under tensile, flexural, and compressive loading. Results are reported as the mean ± standard deviation from three specimens per condition. In standard tensile specimens, PLA reached its highest failure load at 60% infill (1034.7 ± 5.8 N), whereas PETG increased with infill density, reaching 919.0 ± 16.5 N at 100% infill. Under flexural loading, the highest standard-specimen values were 38.7 ± 1.2 N for PLA and 20.0 ± 1.0 N for PETG, both at 90% infill. In compression, PLA standard specimens reached 98,645 ± 448 N at 100% infill, while PETG reached 47,292 ± 16,139 N. For cellular compression specimens manufactured at 90% infill, PLA showed higher failure load values than PETG in all evaluated geometries, with re-entrant honeycomb and EigenModes reaching 9424 ± 1327 N and 9172 ± 157 N, respectively. Scanning electron microscopy indicated brittle fracture and interlayer microcracking in PLA, while PETG showed greater deformation tolerance around voids and local discontinuities. Overall, the mechanical response depended on polymer behavior, loading mode, infill density, and cellular topology. Since Poisson’s ratio was not directly measured, auxetic-inspired metamaterial refers to architectures commonly associated with auxetic behavior in the literature.