Multi-scale topology optimization with shell and interface layers for additive manufacturing

Abstract

Abstract This paper contributes a multi-scale topology optimization method for lattice structure design with both shell and lattice-lattice interface layers to enhance the structural aesthetical, mechanical, and manufacturability properties. To improve the robustness, a multi-step algorithm is proposed. The variable thickness sheet (VTS) method and the projection-based regularization mechanism are used to realize the free material optimization with a limited number of lattice microstructures. Then, a series of successive filtering and projection operations are adopted to identify the lattice-lattice interface layers based on the material density distribution. Elements with close densities are grouped into clusters and for elements inside each cluster, they are assumed to have the same periodical lattice microstructure. In the second step, based on the achieved discrete material distribution, the macrostructure with a solid shell layer and the multiple representative lattice microstructures are concurrently optimized with the density-based multi-scale topology optimization method. Several benchmark numerical examples are studied to demonstrate the effectiveness of the proposed method. Finally, additive manufacturing experiments are performed to validate the stiffness enhancement by including the lattice-lattice interface layers.