Density penalty-based interface identification in shell–infill topology optimization

This paper introduces a density penalty-based topology optimization method for designing shell–infill structures. During the optimization, the shell is identified by simultaneously penalizing density variables of both the solid and the void phases. Two-phase density filtering and Boolean operations are further applied to model the shell–infill structure. In the optimization of shell–infill structures, the shell thickness is controlled through density filtering and the density penalty. For explicit control of the shell thickness, its analytical relationship with the filter radius and the penalty parameter is derived. Both 2D and 3D numerical examples are investigated to showcase the effectiveness of the shell–infill optimization approach. The effects of mass constraints, filter radius, penalty parameter, mesh resolution, and material properties are thoroughly studied. The results demonstrate that the density penalty-based method can efficiently identify interfaces for different settings in shell–infill optimization. The presented formulations can be directly integrated into the optimization process, offering a new perspective for the design of shell–infill structures.