Effect of 3D grading thickness on mechanical and deformation behaviour of gyroid structures produced via powder bed fusion with electron beam

The production of complex geometries with geometrical tuned features is made possible by Additive manufacturing (AM) processes. Powder Bed Fusion using Electron Beam (PBF-EB) is one of the AM techniques for metallic components, which stands out for its ability to fabricate intricate structures with high-performance materials. One example is surface-based architectures known as Triply Periodic Minimal Surfaces (TPMS), where structural walls are defined by a specific thickness. The mechanical behaviour and deformation mechanisms of TPMS are governed by both the geometry and the wall thickness of the structure. Conventional TPMS designs typically employ a uniform or one-dimensional thickness gradient, which constrains their performance under varied loading conditions. This study explores a novel approach involving three-dimensional thickness gradation, aiming to enhance structural integrity, improve load-bearing capacity, and enable functional optimisation. The gyroid surface, a widely studied TPMS for applications ranging from lightweight aerospace components to biomedical implants, is used as a reference geometry. Three types of initiator surface (diagonal plane, cross-shape, and sphere) are employed to create spatial variations in wall thickness between predefined minimum and maximum values. Samples are fabricated using the PBF-EB process, and the resulting structures are characterised via X-ray computed tomography to assess morphometric parameters. These parameters are then correlated with mechanical properties and deformation mechanisms and compared against gyroid TPMS with uniform thickness. The results reveal a significant influence of 3D thickness variation on performance, offering new insights for the design and additive manufacturing of next-generation TPMS structures with tailored mechanical responses.