Mechanical Design and Properties Characterization of Additively-Manufactured Microlattice Structures

Lijun Xiao, Weidong Song^* ,Shi Li

Beijing Institute of Technology, Beijing, 100081, China

ABSTRACT: Lightweight design of materials and structures is an eternal theme pursued in the fields of aerospace, transportation industry and national defense equipment. Microlattice structures have received extensive attention from scholars due to their ultra-lightweight, high specific strength/rigidity, structural designability and excellent energy absorption capabilities. In recent years, with the rapid development of advanced manufacturing technologies such as additive manufacturing, it becomes more and more convenient for the fabrication of new ultra-lightweight microlattice structures. Therefore, it is of great significance to conduct the mechanical property design and characterization of the additively-manufactured microlattice structures. This paper systematically investigated the preparation process, mesoscopic structure and macroscopic behavior of the materials. Firstly, experimental research was carried out on titanium alloy matrix materials and microlattice materials printed by different additive manufacturing processes. Combining with the microstructural characterization, the influence of preparation process and sample size on the mechanical properties of the materials was determined. Considering the different deformation mechanisms of micro-lattice materials, the correlation of the macroscopic properties of the specimens and geometric defects was detected by using X-ray tomography and 3D microscopic finite element analysis. Meanwhile, the high-temperature properties and dynamic failure mechanism of  titanium alloy micro-lattice materials were discussed. Inspired by the characteristics such as gradient mesostructure in natural biomaterials, different design methods including density gradient, multi-cell hybrid and hierarchical structure of microlattice materials were proposed. Accordingly, the mechanical response of the newly proposed microlattice materials under different impact speeds was investigated through experiments and numerical simulations, revealing the macro and mesoscopic failure mechanism of these materials. The above research results provide guiding significance for the mechanical performance characterization and meso-optimization design of additively-manufactured microlattice materials.