Stiffness Optimized Structures with Variable Density Gyroid Lattice Infill for Extrusion Additive Manufacturing

Additive manufacturing has enabled the fabrication of sparse lattice structures with complex geometries tailored to specific uses. These lattice infills provide attractive properties while weighing less than a fully solid part and satisfying the strength and stiffness requirements. Historically, variations in infill lattices have altered either the global geometry or the infill wall thickness to increase strength in high load regions of structures. In this work we expand the generation of these lattices to continuously vary the local infill density at each point within the part volume, allowing for further customization of the mechanical properties. Enabled by a modified penalty-based topology optimization method and an adaptation of frequency modulation, this work continuously optimizes the density of lattice infill geometry while maintaining a constant wall thickness to maximize print performance, mechanical properties, and infill continuity throughout the structure with deposition-based fabrication. These stiffness-optimized lattice structures were successfully printed, tested, and compared to equivalent constant density structures, resulting in stiffness increases from up to 15.8% without impact to material usage or fabrication time. By increasing the stiffness to mass ratio of structures through this infill, it allows for increased adoption of 3D printed components in aerospace, medical, and other applications.