Fractal Analysis and Mechanical Characterization of 3D-Printed Concave Hexagonal Structures With Negative Poisson's Ratio

Materials with a negative Poisson's ratio have gained attention for their unique mechanical properties, enabling applications in aerospace, construction, and medicine. However, the complex geometry of such structures poses challenges for traditional manufacturing. 3D printing offers a solution, allowing precise fabrication of these intricate designs. This study uses 3D printing to create three types of structures from PLA: concave hexagonal, four-directional chiral, and biomimetic feather structures. Tensile testing revealed that the concave hexagonal structure outperformed the others in mechanical strength. Finite element simulations confirmed its superior load-bearing capacity during fracture. Additionally, fractal analysis showed the concave hexagonal structure had the highest fractal dimension in crack propagation, further validating its mechanical superiority. These findings highlight the concave hexagonal structure's advantages through experimental, numerical, and fractal analyses.