Discussing size effect on topological design of periodic unit cells in sandwich core

In the topological optimization problem, objective functions are respectively the maximization of bending stiffness and that of the first order eigen-frequency of sandwich panels under a given volume constraint. Sections 1 and 2 explain the topological optimization work we did; the optimization results are presented in Tables 1 through 6 and Figs. 2, 4 and 6. The core of sections 1 and 2 is: ″the variable-linking technique and the dual optimization scheme are used to design the 3D representative volume elements of the sandwich core with size variation. the upper and lower skins of sandwich panels are non-designable domains.″ On the basis of the above-mentioned optimization results, section 3 deeply analyzes and discusses the effect of the size and volume fraction of unit cell on the configuration design of sandwich core.