Quasi-static and dynamic fracture of additively manufactured AlSi10Mg lattice structures

Prominent industries are increasingly turning to aluminum structures due to their exceptional strength-to-weight ratio. The advent of additive manufacturing (AM) technology has revolutionized the landscape, enabling the production of intricate 3D architectures with unparalleled quality. AM provides the opportunity to produce complex shapes while reducing the lead time and manufacturing costs compared to conventional manufacturing. The lattice structure exemplifies such promising structures owing to its commendable fracture resistance, high specific strength, and thermal advantages. While numerous studies have investigated the strength characteristics of lattice structures, there is a relative scarcity of research focusing on the fracture mechanisms of these structures, particularly under dynamic loading conditions. We fabricated fracture specimens for quasi-static and dynamic testing. Mode I quasi-static experiments were performed, utilizing an Instron screw-driven testing machine. Dynamic Mode I and Mode II fracture tests were carried out using a Split Hopkinson Pressure Bar (SHPB) apparatus for one-point impact configuration. These experiments were supplemented with high-speed video recording, thermal imaging, and Finite Element Analysis (FEA) to improve the interpretation of the results. The primary conclusions of this research are that under static and dynamic loading conditions, fracture initiation in this class of low- ductility materials does not initiate at the notch tip, as could be expected from the presence of a stress concentrator. Rather, crack propagation proceeds through the sequential formation of micro-cracks that develop along the struts in the plane of the applied load. Based on the dynamic tensile characterization of the material, it is also found that for finite element analyses (FEA), a maximum positive tensile strain failure criterion adequately reproduces the struts' failure sequence, paving the way to simple design possibilities.