A static and high-cycle fatigue characterization framework of metallic lattice structures additive manufactured via fused deposition modeling based method

Compared to conventional metal additive manufacturing techniques, metal fused deposition modeling (Metal FDM) reduces cost at the expense of deterioration in materials' mechanical performance. To realize the full design potential that Metal FDM components can offer, effectively predicting the performance becomes imperative, especially for lattice structures that are widely used in aerospace under complex and cyclic loading. This work developed a framework for characterizing and predicting static and high-cycle fatigue behaviors of FDMprinted metal lattices. Constitutive model constants of FDM-printed 17-4PH steels were identified via experiments on dog bone samples at the same length scale of lattice microstructures. The material exhibits quasi-brittle behavior at microstructural size, with a tensile stiffness of 24 GPa. It is only 13 % of the expected stiffness for macroscopic level materials, showing a severe effect by length scale. Residual porosity leads to microcracks, which act as the primary failure mechanism under high-cycle fatigue, reducing the fatigue limit to 31 % of rolled steel. Assigning developed constitutive models, the asymptotic homogenization method was employed to obtain equivalent static properties of stretch- and bend-dominated lattices, which were in accord with testing results. Through the Brown-Miller-Morrow method, the framework numerically predicted lattice high-cycle fatigue life, which was validated against experiments.