Parametric Investigation of Reentrant Hexagonal Auxetic Honeycombs Under Tension Mechanical Response and Fractal Characterization of Crack Paths

Auxetic structures with negative Poisson's ratio show promise in aerospace, automotive, and healthcare applications due to their energy absorption and impact resistance. However, most studies focus on compression, leaving tensile deformation mechanisms underexplored. This work investigates reentrant hexagonal auxetic structures with varying strut ratios (2, 2.5, 3) and reentrant angles (40°–80°), fabricated via FDM 3D printing using PLA. Uniaxial tensile tests and finite element simulations were performed to evaluate stress–strain behavior, Poisson's ratio evolution, and failure. Fractal theory quantified crack paths. Results show that increasing strut ratio raises maximum stress but reduces fracture strain. Larger reentrant angles decrease modulus and maximum stress while increasing fracture strain. Energy absorption peaks at 50°–60°. Fractal dimension reveals complex crack paths at 50°–70°, corresponding to optimal absorption. This study elucidates the coupled effects of strut ratio and reentrant angle on tensile behavior, offering insights for multiparameter optimization of auxetic structures.