Multi-scale topological design of asymmetric porous sandwich structures with unidentical face sheets and composite core.

• A novel multiscale topology optimization method is proposed for designing asymmetric porous sandwich structures. • Multi-material sandwich structures are topologically optimized using the proposed method. • The thickness and material of two face sheets and the configuration of composite cores are simultaneously optimized. • Parametric level set method and alternating active-phase method are adopted. • Several 2D and 3D numerical examples are investigated and compared. Compared with conventional symmetric sandwich structure with identical face sheets and single-material core, asymmetric porous sandwich structures (APSSs), which are composed of unidentical face sheets and composite core, usually take better advantage of all materials and provide superior bending stiffness. However, current studies regarding the APSSs are mainly analytical- and experimental-based methods with predefined face sheet thicknesses and core configurations, which greatly confines the potential loading capacity of sandwich structures. This paper develops a multiscale topology optimization method for the multi-material APSSs, which can realize the designs of the thickness and material of two face sheets at macroscale as well as the configuration of composite cores at microscale for minimizing structural compliance. Firstly, at macroscale, a multi-material variable thickness sheet method integrated with an alternating active-phase algorithm are employed to optimize the thickness and material of two solid face sheets. Then, at microscale, a difference-set-based multi-material level set (DS-MMLS) model is applied to represent the topology of each material phase within sandwich core, and their topological evolution can be readily achieved by using a parametric level set method also combined with the alternating active phase algorithm. Several 2D and 3D numerical examples are provided to show the effectiveness and advantages of the proposed method. The results indicate that compliances of the optimized APSSs show superior advantages over some conventional sandwich structures with predefined design features. [ABSTRACT FROM AUTHOR]