Evolution Mechanism of Unit Cell and Performance Forward Design of N -1 Type Polyhedral Sandwich Structure

N-1 type polyhedral sandwich structure is a kind of sandwich structure which has the advantages of high specific strength, good heat resistance and impact resistance. In the process of structure optimization, the complexity of design space and calculation lead to local optimum results. In order to solve this problem, forward design method for shear performance of N-1 type polyhedral sandwich structure based on the evolution mechanism of unit cell is proposed. Firstly, the geometric feature of N-1 type polyhedral unit cell is analyzed. The fundamental cells and evolutionary circles are defined. N-1 type polyhedral unit cells were divided into tangent cells, outer intersected cells and inner intersected cells. Secondly, the similarity evolution pattern of N-1 type polyhedral unit cell is constructed based on basic cell and evolutionary circles. The evolution mechanisms between 2 D topology and 3 D topology is obtained. And the feasible windows of unit cell evolution are put forward by calculating the feasible domain of evolution parameters. Thirdly, optimization domain and spatial distribution of N-1 type polyhedral sandwich structure shear performance are determined by analyzing the relationship between evolution parameters, thickness and shear properties. Then, the optimization model for shear performance of N-1 type polyhedral sandwich structure is established based on the Kriging approximation technique and obtained the N-1 polyhedral sandwich panel with globally optimal shear performance. Finally, the reliability of the structure is verified by comparison with the corrugated sandwich structure, which provides a theoretical basis for designing the regular polyhedral sandwich structure.