Additive Manufacturing of Metal Cellular Structures: Design and Fabrication LI YANG, 1,4 OLA HARRYSSON, 2 DENIS CORMIER, 3 HARVEY WEST, 2 HAIJUN GONG, 1 and BRENT STUCKER 1 1.—Department of Industrial Engineering, University of Louisville, Louisville, KY 40292, USA. 2.—Department of Industrial & System Engineering, North Carolina State University, Raleigh, NC 27695, USA. 3.—Department of Industrial & System Engineering, Rochester Institute of Technology, Rochester, NY 14623, USA. 4.—e-mail: li.yang.1@louisville.edu With the rapid development of additive manufacturing (AM), high-quality fabrication of lightweight design-efficient structures no longer poses an in- surmountable challenge. On the other hand, much of the current research and development with AM technologies still focuses on material and process de- velopment. With the design for additive manufacturing in mind, this article explores the design issue for lightweight cellular structures that could be efficiently realized via AM processes. A unit-cell-based modeling approach that combines experimentation and limited-scale simulation was demon- strated, and it was suggested that this approach could potentially lead to computationally efficient design optimizations with the lightweight structures in future applications. INTRODUCTION In recent years, additive manufacturing (AM) has received considerable attention for its potential in transforming global manufacturing industries. In some of the leading application areas such as aerospace, biomedical, and automotive, AM has demonstrated unprecedented flexibility for part con- solidation, function integration, and lightweighting of structure and component designs. 1–3 Lightweight de- sign is one area that AM addresses well where other traditional manufacturing technologies become largely impractical. 4–6 Because of the requirements for design optimization and the complex resulting geometries, full-freedom lightweight design often involves multiscale analysis, which makes pure finite- element based design computationally demanding. Topology optimization methods have been investi- gated as a feasible solution. 7–9 However, currently topology optimization has been used only for max- imum stiffness design to date, and it lacks sufficient capabilities for hierarchical design integrations at multiple scales. Another common approach that at- tempts to achieve the blalance between design con- venience/efficiency and design accuracy is the unit cell design approach, which uses representative geome- tries to efficiently perform design tasks. Cellular structures are characterized by the large percentage of porosity in the solids 10 and can often be treated as assemblies of cells with solid edges or faces. 11 In past decades, cellular structures have received a lot of interest due to their promising potential in a wide range of engineering applica- tions. 10–13 It is well known that cellular structures exhibit a combination of mechanical and thermal properties such as high stiffness-to-weight ratio, 11,13–15 high energy absorption, 16–18 and low heat conduc- tivity, 19 which are highly desired in applications such as aerospace structures, automobiles components, stiffening spatial fillers, impact cushions, thermal in- sulations, sandwich cores, vibration dampers, and civil structures. 13 In addition, due to their large surface areas, cellular structures are also extensively used as catalysts and filters 10,14, 20,21 and biological inter- faces. 22–24 The unique advantage of adopting analytical modeling-based cellular design is that it becomes possible to integrate multiple design objectives and to achieve a combination of mechanical properties through design optimization. This is enabled by the explicit geometry–property relationships of the rep- resentative unit cells, which have simplified forms and could be readily manipulated via optimization methods. Traditionally, due to manufacturability JOM DOI: 10.1007/s11837-015-1322-y Ó 2015 The Minerals, Metals & Materials Society