Multi jet fusion printing of heterogeneous lamellar lattice structures with superior mechanical properties

• Main Author: Hou, Boyuan
• Other Authors: Zhou Kun
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Heterogeneous lamellar lattice structures
• Online Access: https://hdl.handle.net/10356/176860
• Institution: Nanyang Technological University

Recent research and application of additive manufacturing (AM), also referred to as three-dimensional (3D) printing, have both increased. The layer-by-layer nature of 3D printing offers design freedom and allows for fabricating structures with delicate geometries and outstanding properties. Powder bed fusion (PBF) is a 3D printing technique that employs a focused energy source to selectively fuse or consolidate powdered materials layer by layer, resulting in the formation of complex 3D structures. Multi Jet Fusion (MJF), a fast-growing PBF technique, can produce high-quality, functional parts while increasing productivity. Lattice structures can be created using MJF. These structures have been extensively employed as protective layer in various fields due to high specific energy absorption and specific strength. However, the shear bands often appear in these structures subjected to compression, inducing an unstable mechanical response and significant reduction in their energy absorption and loading-bearing capacities. Here, we leverage the design freedom offered by additive manufacturing and the geometrical relation of dual-phase nanolamellar crystals, for the first time, to fabricate heterogeneous lamellar lattice structures consisting of body-centered cubic (BCC) and face-centered cubic (FCC) unit cells in alternating lamella. The lamellar lattice structures achieve a favourable combination of elevated plateau stress, stable stress response, enhanced specific strength, and improved specific energy absorption (SEA) and energy absorption efficiency (EAE). Specifically, a heterogeneous lamellar lattice structure demonstrates more than 10 and 9 times higher specific energy absorption and energy absorption efficiency, respectively, than the BCC lattice. This dramatic improvement in energy absorption capacity arises because the nucleation of shear bands is inhibited by the discrete energy threshold for plastic buckling of the adjacent heterogeneous lattice lamella during loading, thus avoiding global catastrophic failure. Compared with the FCC lattice, the plateau stress of the lamellar lattice are improved significantly despite its lower density, which is ascribed to the strengthening effect induced by the simultaneous deformation of unit cells in the soft BCC lattice lamella and the resulting cushion shielding effect. The designed lamellar lattice compares favourably against a wide range of lightweight structures and materials proposed for mechanical protection. This approach opens new avenues for lattice structure design, leading to improved overall mechanical performance, paves the way for advanced mechanical protection solutions in aerospace, transportation, and military applications.