Mechanical performance of equilateral triangular lattices: The role of nodal fillets

Triangular lattices are widely employed for their high strength to weight ratios, yet their mechanical performance is sensitive to geometric features, particularly the nodal geometry. This study investigates the influence of nodal geometry on the mechanical behavior of equilateral triangular lattices across a broad range of relative densities using high fidelity finite element simulations. We characterize the elastic properties, and strength limits as functions of fillet radius. Our results confirm the expected trend that, in stretching-dominated lattices with low relative density, the introduction of fillets reduces both stiffness and buckling resistance. In contrast, at higher relative densities, filleted nodes can alter the load bearing mechanism and enhance both stiffness and structural stability. Across all ranges of relative density, fillets are effective in mitigating stress concentrations, resulting in notable improvements in yield strength. Optimal nodal configurations are identified, achieving up to 80% of the yield strength predicted by simple beam models that neglect nodal effects and effective stiffness values that approach or exceed the non filleted configuration. Finally, the results are synthesized into a design guideline for selecting the optimum fillet radius to enhance the strength of equilateral triangular lattices, and serving as a quick and practical tool for researchers and engineers to identify the best nodal configuration. • The impact of nodal fillet geometry on the mechanical properties of triangular lattices is investigated. • Elastic, yield, and buckling responses are analyzed across a wide range of relative densities. • Design guidelines are established based on material properties and failure modes.