Design of shell-infill structures by a multiscale level set topology optimization method

Abstract

Shell-infill structures are widely used in additive manufacturing (AM) to retain the external appearance and reduce the printing costs. However, shell-infill structures are generally designed by a mono-scale topology optimization method. In this case, these shell-infill structures are not optimal designs due to their incompatible shell and infill layouts. In order to obtain the optimized shell and infill simultaneously, this paper presents a multiscale level set topology optimization method for designing shell-infill structures. In macroscale optimization, two distinct level sets of a single level set function (LSF) are used to represent the interface of the shell and the infill, respectively. The thickness of the shell is assumed to be uniform, which is guaranteed by a level set reinitialization scheme. In microscale optimization, the pattern of the microstructure is optimized to achieve the optimal macro structural performance. The numerical homogenization method is applied to evaluate the effective elasticity matrix of the microstructural infill. The shell-coated macro structure and the micro infill are optimized concurrently to achieve the optimal shell-infill design with prescribed volume fractions. Both 2D and 3D examples are investigated to demonstrate the effectiveness of the presented method.