Topology optimization of sandwich structures with solid-porous hybrid infill under geometric constraints

Topology optimization of sandwich structures is attracting more interests due to its potential to balance mechanical performances and lightweight level, especially with the increasing application of additive manufacturing. This paper presents a topology optimization method to generate sandwich structures with solid-porous hybrid infill, in which this design feature of hybrid infill will improve the structural performance such as stiffness-to-weight ratio and strength-to-weight ratio, compared to designs with pure porous infill. Two design variable fields are introduced to describe the fundamental topology, in which one used to determine corresponding shell and infill domain through two-step density filtering under the SIMP framework, while another for assigning each solid-type or porous-type material into the infill domain. A projection-based geometric constraint method is developed to restrict the maximum size of solid infill, leading to solid infill distributed at the expected regions for manufacturing concerns. Furthermore, compliance-minimization topology design problem under mass constraints of solid and porous materials is formulated and solved with MMA in combination with the derived sensitivities. Three numerical examples are systematically investigated to demonstrate the effectiveness of the proposed method.