Design and fabrication of additively manufactured functionally graded porous structures

Energy-absorbing materials like cellular solids can reduce the impact load and dissipate the impact energy. They have gained attention because of their high energy absorption efficiency and excellent design flexibility. However, it is difficult for traditional manufacturing techniques to obtain the design flexibility of cellular solids, which can be achieved by the emerging additive manufacturing technique. The combination of cellular solids and additive manufacturing lays the foundation for developing advanced materials in key scientific fields. Therefore the authors overview the recent progress on additively manufactured cellular solids. Three main additive manufacturing technologies for producing cellular solids, including powder bed fusion, material extrusion, and vat photopolymerization, are first introduced. Five kinds of additively manufactured cellular solids, including open-cell foam, closed-cell foam, 2D honeycomb, 3D lattice, and gradient cellular solids, are then discussed. Finally, the authors indicate major ongoing scientific issues for future research.