High- and low-fidelity modal and mechanical analysis of architected strut-based lattice structures with auxetic topologies

This study presents an in-depth numerical investigation of the dynamic and mechanical performance of architected, strut-based lattice structures, with a critical emphasis on auxetic topologies, such as double pyramids with and without lateral supports. Finite element simulations using both high-fidelity (actual) and low-fidelity (homogenized) models are carried out across various lattice geometries, including octet, diamond, cubic variants, and double pyramids, spanning unit cell configurations from 1 × 1 × 1 to 5 × 5 × 5. The modal analysis reveals that homogenized models provide excellent agreement for geometrically regular and isotropic lattices, such as the octet. However, they tend to significantly overpredict lower-order natural frequencies in complex or auxetic architectures, especially at smaller scales. A threshold of 3 × 3 × 3 unit cells is identified for achieving reliable homogenization in anisotropic lattices. Effective mechanical properties using periodic boundary conditions were also studied, confirming auxetic behavior (negative Poisson's ratio) in selected configurations. Furthermore, the inclusion of rounded fillets at sharp junctions in the lattices enhances both stiffness and modal accuracy. Notably, modal degeneracy observed in specific symmetric geometries underscores the role of topology in vibrational behavior. This work offers comprehensive design guidance for tailoring lattice-based materials in high-performance applications, enabling optimized fidelity selection and resonance avoidance strategies in aerospace, biomedical, and multifunctional composite systems.