This article presents a topology optimization method for structures consisting of multiple lattice components under a certain size, which can be manufactured with an additive manufacturing machine with a size limit and assembled via conventional joining processes, such as welding, gluing, riveting, and bolting. The proposed method can simultaneously optimize overall structural topology, partitioning to multiple components and functionally graded lattices within each component. The functionally graded lattice infill with guaranteed connectivity is realized by applying the Helmholtz PDE filter with a variable radius on the density field in the solid isotropic material with penalization (SIMP) method.The partitioning of an overall structure into multiple components is realized by applying the discrete material optimization (DMO) method, in which each material is interpreted as each component, and the size limit for each component imposed by a chosen additive manufacturing machine. A gradient-free coating filter realizes bulk solid boundaries for each component, which provide continuous mating surfaces between adjacent components to enable the subsequent joining. The structural interfaces between the bulk solid boundaries are extracted and assigned a distinct material property, which model the joints between the adjacent components. Several numeral examples are solved for demonstration.
K E Y W O R D Sbulk solid interfaces, lattice infill, multicomponent structures, topology optimization
INTRODUCTIONLattice structures exhibit superior structural properties such as low stiffness-to-weight ratio, robustness for random direction loads, damage resistance against defects, and extreme physical properties such as large energy absorption, 1,2 negative Poisson's ratio, 3,4 large thermal expansion, 5,6 and special acoustic absorption. 7,8 Owing to the recent advancement in additive manufacturing processes, especially those in metals, the fabrication and testing of engineered lattice structures have become much more accessible to researchers. Thompson et al. 9 reviewed recent work on design for additive manufacturing including the design of engineered lattice structures. They pointed out there was still a lack of systematic design method to overcome the complexity of lattice structures whose dimension spans from the micro/meso-scale to macro-scale. In addition to the structural complexity, additively manufactured lattice structures for industrial applications