Multiscale Topology Optimization Combining Density-Based Optimization and Lattice Enhancement for Additive Manufacturing

Topology optimization (TO) is a shape optimization method based on finite element (FE) analysis, and has recently been used in lightweight design on the basis of the rapid advances of additive manufacturing (AM). While the conventional TO has been applied to obtain the optimal pseudo density in a macroscale domain, microscale TO involving optimization of the strut diameters of a lattice structure has also been studied. In this study, a multiscale TO method was developed by performing the conventional macroscale TO with additional enhancement of microscale lattices. To compare the structural efficiency of the proposed multiscale TO with that of the macroscale and microscale TOs, three optimization methods were applied to a meta-sandwich beam under a three-point bending load condition. Structural FE analyses were then conducted for the three optimized beams, and their deformation behaviors were compared in terms of the structural stiffness and safety. Three optimized beams were then fabricated by the photo-polymerization type AM process using an acrylic photopolymer, and bending experiments were conducted to investigate their deformation behaviors. From the results, the multiscale TO showed the highest structural stiffness and strength owing to the enhancement of microscale lattices. The energy absorption capability was also improved compared to the result of the macroscale TO. These results demonstrate that the multiscale TO is advantageous in the design of efficient lightweight structures with enhanced structural stiffness and safety compared to the conventional macroscale and microscale TO methods.