3D Printing and Mechanical Behavior of Anisogrid Composite Lattice Cylindrical Structures

Anisogrid cylindrical lattice (ACL) structures have been successfully used in space applications, demonstrating high mechanical performance and weight efficiency. However, the manufacturing process for the composite ACL structures is very complex and, traditionally, involves different technologies, including winding of filaments or prepregs and curing. Tacking the advantage of the fused deposition modeling (FDM) to manufacture completely integral composite parts with complex shape, in this paper, the FDM-3D printing of ACL structures using carbon fiber (CF) and glass fiber (GF) reinforced polyamide 12 (PA12) composites has been investigated. The mechanical behavior of 3D printed ACL structures has been analyzed in terms of the static stiffness, specific load, and failure mode through axial and transverse compression tests, as a function of the geometrical parameters of the lattice structure. It was observed that, under transverse compression, after the initial linear elastic response, the applied load changed its slope and continued to increase with increasing displacement up to a specified displacement (inner radius of the ACL structures) without visible fracture or delamination between layers, demonstrating that the 3D printed composite ACL structures are robust and highly efficient in the nodes. Under axial compression, the applied load increased with displacement up to a maximum load and then decreased until fracture, mainly, due to local buckling and material failure of the helical ribs. The 3D printed CF/PA12 ACL structures were found to be more efficient than either the GF/PA12 or PA12 ACL structures taking into account both the axial and transverse specific load and stiffness. The increase in the shell thickness, helical rib width or number of helical ribs resulted in a remarkable increase in the stiffness and load-bearing capacity of the 3D printed composite ACL structures. From the manufacturing perspective, it was shown that the FDM-3D printing technology holds promise for the development of mechanically robust composite ACL structures with excellent reliability.