Study on Advanced 3D Printed Lattices

Abstract

This thesis investigates the mechanical properties of 3D-printed lattices made of convex and re-entrant tetrakaidecahedron cells with different methods. In the first part of the research, cubic lattices based on tetrakaidecahedron cells with re-entrant ribs were fabricated via Select Laser Sintering (SLS) with Nylon 6 powder. The examination revealed a notable decrease in Poisson's ratio with smaller re-entrant angles and slenderer ribs, while convex tetrakaidecahedron cells exhibited a Poisson's ratio near 0.5, with rib slenderness exerting minimal influence compared to re-entrant lattices. In subsequent experiments, the mechanical properties and deformation behavior of 3D printed lattice with tetrakaidecahedron unit cells were explored. Compression tests, laser reflection experiments, and tensile testing were employed to investigate the viscoelastic characteristics and modulus of the printed materials. Small differences in viscoelasticity between the lattice and solid specimens were found, with the lattice has the least viscous behavior. Furthermore, comparative analysis between horizontally and vertically printed solid specimens shows the influence of printing orientation on material properties. Additionally, laser reflection experiments were used to discover the non-classical bulge phenomenon, which is a distinctive behavior of Cosserat solids. These comprehensive insights contribute to a deeper understanding of material responses in 3D printed structures. The last part of the experiments uses holography to find the bending modulus of the same 3D-printed tetrakaidecahedron lattice. Initial testing with a screw-driven test frame yielded a modulus of approximately 27±5 MPa, and holography methods gives the result of 24 ± 5 MPa.