CFGLSs: Conformal filling gradient lattice structures designed by multiscale isogeometric topology optimization for 3D swept volume

3D swept volume, enabled by advancements in additive manufacturing, present new opportunities for lightweight and functional optimization. However, efficient design methodologies for conformal filling gradient lattice structures (CFGLSs) remain scarce. This paper proposes a modified level set function (MLSF) that matches lattice structures to the geometry of 3D swept volume. Furthermore, a multiscale isogeometric topology optimization (MITO) approach is used to adaptively optimize the distribution of graded lattices, ensuring optimal integration. A surrogate constitutive model is developed using polynomial interpolation in conjunction with the MLSF and the homogenization method. Incorporating the surrogate constitutive model into the MITO, the relative density distribution of the swept volume is obtained. Continuous CFGLSs are generated using the updated MLSF method, with the equivalent density distribution guiding the simultaneous optimization of both the micro-scale lattice geometry and its macro-scale distribution. The proposed approach is validated through the design, fabrication, and experimental evaluation of semi-circular specimens and engineering rudders, exhibiting its effectiveness and practicality.