Experimental-assisted design development for an octahedral cellular structure using additive manufacturing

Abstract

Purpose – This paper aims to demonstrate the design and verification of a 3D reticulate octahedral cellular structure using both analytical modeling and additive manufacturing. Traditionally, it has been difficult to develop and verify designs for 3D cellular structures due to their design complexity. Design/methodology/approach – Unit cell modeling approach was used to model the octahedral cellular structure. By applying structural symmetry simplification, the cellular structure was simplified into a representative geometry that could be further designed with a standard beam theory. The verification samples were fabricated with EBM process using Ti6Al4V as materials, and compressive testing were performed to evaluate their properties. In addition, designs with different number of unit cells were investigated to evaluate their size effect. Findings – Explicit mechanical property design (including modulus and compressive strength) of the octahedral cellular structure was realized via parametric equations driven by geometrical designs and material types. In addition, it was verified both numerically and experimentally that the octahedral cellular structure exhibit unusual size effect, which is highly predictable. Unlike some of the other cellular structures, the octahedral cellular structure exhibits softening behavior when the number of unit cell increases between the sandwich skins, which could be explained by the upsetting effect commonly observed in bulk deformation processes. Originality/value – This paper established a more comprehensive understanding in the design of octahedral cellular structures, which could enable this type of structure to be designed for sandwich structures with higher fidelity. Therefore, this study not only demonstrated an efficient methodology to design 3D cellular structures using additive manufacturing, but also facilitated the development of design for an additive manufacturing theory.