Mechanical properties of three-dimensional functionally graded triply periodic minimum surface structures

Lattice structures based on triply periodic minimum surfaces (TPMS) have received extensive attention due to their superior light-weighting and energy absorption properties. To generate a more competent design to accommodate multi-directional loading conditions in real-life applications, a three-dimensional functionally graded (FG-3D) TPMS structure was proposed in this study. Selective laser melting (SLM) was utilized to fabricate the designed TPMS lattice structures with Ti-6Al-4 V powder. They were investigated experimentally and numerically in terms of mechanical properties under different loading directions. The results indicated that the FG-3D Primitive (P) and Gyroid (G) structures can absorb 45.3% and 12% more energy than the uniform counterparts, respectively, and exhibit excellent energy absorption capacity under different loading directions. In contrast, the mechanical properties of both one- and two-dimensional FG structures might be inferior in some loading directions. Meanwhile, the parametric study of FG-3D structures was conducted and found that a large volume fraction and proper range of gradient variation are preferable for improving the energy absorption capability. These findings can provide guidelines on gradient design strategies, which can promote the application of energy-absorbing structures in real-life engineering.