Optimization Design And Performance Analysis Of 3D Lattice Material With Zero-expansion And High Ultra-stiff

The aerospace structures' stability and detection instruments' testing accuracy will be challenged by thermal issues when operate in ultra-high,low temperature or rapid temperature changes service environment.In order to prevent precision structures or equipment from losing their original design functions under the influence of thermal deformation or thermal stress,it is very urgent to design materials with thermal stability.As a structured material,lattice materials have excellent properties such as high porosity,ultra-stiffness,heat insulation,and strong designability,which have a high degree of matching with the lightweight and versatility of materials in the aerospace field.So,it is a very suitable choice for designing zero/low expansion materials.The paper aims to design materials that can help to improve the thermal stability of aerospace structures and related electronic equipment.A series of research work has been carried out on the optimal design,performance analysis and preparation of 3D metal lattice materials with ultra-stiffness and zero-expansion properties.The details are as follows:1.Configuration design of lattice material micro-cell.Combined with the inverse homogenization design idea and the NIAH method,the technical route for multi-functional lattice material design was established.And based on this route,a lattice material micro-cell with ultra-stiffness and specific direction's zero-expansion performance was optimized design,which included topology optimization,size optimization and topography optimization design.Through multiple rounds of calculations,innovative micro-cell was obtained and its thermal deformation mechanism research was carried out.It was pointed out that the direction and size of the thermal deformation of each rod in the innovative micro-cell are different and their mutual constraints are the fundamental reason for it has zero-expansion performance.2.Performance verification and analysis of innovative micro-cell.Based on the finite element calculation,the thermal deformation of the innovative lattice structure under unit temperature rise was calculated to verify the effectiveness of the zero-expansion design.Simultaneously,it was pointed out that the imbalance of the unit cells at the boundary is the essential reason for the thermal deformation of the structure to have the boundary effect.The analysis and discussion of the load-bearing and versatility of the innovative micro-cell were carried out.Based on the Ashby diagram,the specific stiffness of the innovative micro-cell is compared with several advanced materials to prove its superiority in load-bearing performance.The comprehensive comparison result of the bulk modulus and thermal expansion coefficient of micro-unit with various lattice materials shows that the innovative micro-cell has strong versatility.By changing the relative material density,the elastic modulus and thermal expansion coefficient of the innovative micro-cell can be adjusted in a large range,showing a certain degree of performance adjustment ability.3.Improved design of innovative micro-cell for manufacturing.Based on the preparation method of the bimetallic lattice material and the corresponding manufacturing constraints,it was pointed out that the inter-embedding phenomenon of the bimaterials existing in the beam model innovation micro-cell will increase the manufacturing difficulty.Furthermore,the difference between the thermal deformation mode of the beam element and the actual physical phenomenon will result in insufficient accuracy of the thermal deformation simulation results.For the purpose of enhancing practicability and reducing manufacturing difficulty,a solid innovative micro-cell model was established,the material distribution method at the bimaterial junction was adjusted,and the cross-sectional shape of some rods was optimized.Based on the finite element calculation and NIAH method,the thermal deformation and equivalent elastic modulus of the improved solid innovative micro-cells were calculated,which proved that the stiffness and thermal expansion performance were not weakened by the change of modeling method.