This study examines the mechanical behaviour of PLA auxetic lattices produced via fused-filament fabrication, including single topologies (re-entrant, modified re-entrant, star) and hybrid sequences (RSRS, SRSR, RRSS, SSRR). Lattices with 0.8 mm wall thickness were tested under uniaxial compression and tension along X and Y axes, supported by calibrated finite-element models in Ansys. Mesh convergence determined a 0.5 mm tetrahedral size, keeping deformation and stress errors under 2%. Experimental results showed strong anisotropy: star had the highest, nearly isotropic stiffness (≈ 1.7 MPa peak at 0.04% strain), while re-entrant was highly flexible in X but stiffer in Y. Hybridisation reduced directional disparity—RRSS excelled in X-axis compression (133 MPa, 460 N), SSRR absorbed more energy, and SRSR achieved the highest Y-axis tensile resistance (1.502 MPa, 601 N). SSRR remained the most compliant (0.632 MPa). Simulation–experiment errors ranged from 0.77 to 11.9% (compression) to 24–34% (tension), largely due to simplified material modelling. Star and RRSS/SSRR hybrids are optimal for load-bearing, quasi-isotropic stiffness, while modified re-entrant and RSRS/SRSR hybrids suit energy-absorbing designs, offering guidelines for lightweight, impact-resistant structure optimisation.
Cheng et al. (Fri,) studied this question.