Multi-morphology cellular structure design with smooth transition of geometry and homogenized mechanical properties between adjacent cells

Abstract

The recent development of additive manufacturing has led to an increased interest in the study of functionally graded cellular structures, which exhibit superior mechanical properties to the conventional uniform structures. However, connectivity is a critical problem that should be addressed, especially when multiple unit cell topologies are incorporated into a structure. In particular, inappropriate connectivity may cause stress concentration at the interfaces, reducing the structure’s lifespan. This paper proposes a method to design multi-morphology cellular structures that ensures smooth transition of geometry and homogenized mechanical properties between adjacent unit cells. The proposed method uses a genetic algorithm to design intermediate unit cells between a base and a target unit cell. Moreover, a customized parametric unit cell representation supports the design process. An implicit modeling method is adopted to synthesize the explicit 3D models. Numerical analyses demonstrate that the proposed method guarantees smooth transitions of geometry at the interfaces, variations in density, and homogeneous mechanical properties. Moreover, experimental characterization resulted in an increase of 78.7% in the elastic modulus and a reduction of 54.9% in the maximum von Mises stress for the structure designed with the proposed method when compared with that created using the conventional non-smoothing technique.