A parameterization modeling method based on finite element mesh to create complex large-scale lattice structures for AM is presented, and a corresponding approach for size optimization of lattice structures is also developed. In the modeling method, meshing technique is employed to obtain the meshes and nodes of lattice structures for a given geometry. Then, a parametric description of lattice unit cells based on the element type, element nodes and their connecting relationships is developed. Once the unit cell design is selected, the initial lattice structure can be assembled by the unit cells in each finite element. Furthermore, modification of lattice structures can be operated by moving mesh nodes and changing cross-sectional areas of bars. The graded and non-uniform lattice structures can be constructed easily based on the proposed modeling method. Moreover, a size optimization algorithm based on moving iso-surface threshold (MIST) method is proposed to optimize lattice structures for enhancing the mechanical performance. To demonstrate the effectiveness of the proposed method, numerical examples and experimental testing are presented, and experimental testing shows 11% improved stiffness of the optimized non-uniform lattice structure than uniform one.

The lightweight design of the sandwich mirror, as a commonly used space primary mirror structure, is one of the key topics for the design of space-based optomechanical systems. Owing to the limitation of traditional manufacturing capabilities, the induced holes on the mirror back are usually of the open or half-open form, which compresses the optimization design space. With rapid development of additive manufacturing (AM) technologies, it is possible to fabricate a closed-back sandwich mirror with a complex internal structure to achieve outstanding performance. In this paper, a novel topology optimization model for a closed-back primary mirror of a large-aperture space telescope is proposed. First, extrusion constraints are considered in the optimization model to obtain the layout design of stiffening webs inside the mirror core. Then, a simply connected constraint, as one type of constraint in AM, is considered to avoid enclosed voids in the structures. Through solving the proposed model, a new c...

Acoustic metamaterial with negative or near-zero refractive index exhibits extraordinary acoustic transmission characteristics, including acoustic total reflection, acoustic stealth and acoustic tunneling. Based on the coiled-up space structure, a football like near-zero refractive index acoustic metamaterial (FNZIM) was proposed. The result reveals the formation of two transmission peaks at 1270 Hz and 2300 Hz from the equivalent parameters by using the transfer matrix method. The first peak exhibits excellent air impedance matching, while the second peak arising from the metamaterial’s near-zero refractive index. We then constructed an acoustic prism using 15 cells of FNZIM and calculated the dispersion curve, revealing that the near-zero refractive index supernormal transmission of metamaterials is attributable to multimode degeneracy. Furthermore, we find that the positions of the transmission peaks and transmission loss can be adjusted by appropriately altering the structural parameters. Finally, we tested two groups of samples by using impedance tube four-channel to verify the accuracy of the simulation and the validity of insulation performance of FNZIM. The broadband ventilation sound insulation coupled structure is constructed, and the average sound insulation performance of this structure is more than 25 dB in the range of 1140–2210 Hz.