Optimization Design And Experimental Verification Of Mechanical-thermal Properties Of 3D Printed Lattice Sandwich Plate

Truss-like lattice material is an ideal material to realize lightweight and functional structures for the new generation of aerospace equipment.The sandwich lattice structure composed of lattice material has become an ideal structure form for thermal bearing structure due to its excellent material properties(high specific strength and specific stiffness)and good thermal physical properties(heat insulation and heat dissipation).However,the structure of truss-like lattice material is complicated,and the structure composed of lattice material contains a large number of unit cells,so it is often expensive to use fine finite element modeling and analysis directly.Therefore,in this thesis,a series of studies based on the Novel Numerical Implement of Asymptotic Homogenization method(NIAH)have been carried out on the equivalent thermal conductivity coefficient,mechanical performance analysis,experimental validation,and multi-objective optimization of truss-like lattice materials and sandwich lattice structures.The specific research contents are as follows:(1)The NIAH method overcomes the intracellular integration difficulties of different cells in the traditional homogenization method,so the NIAH method is adapted to derive the equivalent thermal conductivity coefficients of unit cells composed of bar elements.The thermal conductivity coefficients of four different sandwich lattice structures of unit cells are obtained by using heat transfer theory and thermal resistance model.The results are compared with those obtained by the thermal resistance model when the sandwich lattice structure representing the volume element to achieve mutual verification.(2)In order to further verify the correctness of the theoretical derivation results and accuracy,with using 3D printing technology and magnesium aluminum-silicon alloy(7)₄10)2))as the base material,four different sandwich lattice structures are manufactured.Then,the thermal conductivity of sandwich lattice structures has been measured using the steady-state method.It further verifies the effectiveness of the thermal conductivity coefficient of lattice core structure based on the NIAH method.At the same time,in order to further reduce the physical experiment error,considering the effect of insufficient density of 3D printed structure on the structural performance,the error correction of the experimental results was carried out.(3)In order to further improve the mechanical properties of the lattice sandwich plate,a two-objective optimization model was established,which takes the bulk modulus and thermal conductivity coefficient as the objectives,the overall mass of the structure as the constraint,and the radius of lattice micro-cell member as the design variable.Three kinds of multi-objective optimization algorithms(NSGA-II,NCGA,AMGA)commonly used in Isight were considered to solve the established multi-objective optimization problem,and the Pareto non-inferior solution set under the three kinds of the multi-objective genetic algorithm was obtained.The obtained non-inferior solution set was better than the target performance of the initial lattice sandwich plate structure.It provides a reference for the engineering application of the lattice sandwich plate.