Stress equalizing in optimal design of High-Toughness lattice structures

In this paper, the recently proposed structural optimization strategy, the Galilei-Optimization (GO), is adapted for improving the toughness response of a holed two-dimensional lattice system made of a network of micro-beams whose geometrical arrangement was prescribed. By taking advantage of the possibility of minimizing stress gradients and stress peaks around the hole via GO, we redesigned the cross sections of the lattice beam elements, equalizing the stresses over the entire domain. Consequently, the resulting optimized microstructure highlighted a significant enhancement of the overall toughness due to a drastic decrease of the stress concentration factor in the hole proximity, preserving the initial stiffness and lowering the total overall weight. To validate the robustness of the procedure and the numerical Finite Element outcomes, two non-optimized and optimized structures were actually built up through 3D printing and tested in the laboratory under the same boundary conditions used for the simulations. This evidence confirmed the effectiveness of the proposed method in obtaining optimized beam-like plates with high toughness, which could pave the way for designing new light materials with extreme mechanical performance well beyond the sole stiffness and strength.