J.R. Kubalak, C.B. Williams
Keywords: topology optimization, toolpath optimization, additive manufacturing
Summary:While there have been significant advancements in composites manufacturing processes (e.g., automated fiber placement and automated tape laying), there are still major opportunities to improve structural performance. The ability to customize fiber orientation through tow steering increases mechanical performance, but the large tool heads and tow widths cannot articulate high degrees of curvature. This restricts potential mechanical efficiency by inhibiting geometric flexibility and imposing a large minimum turning radius on the fiber. Establishing the computational frameworks required to design structures that leverage continuously varied fiber orientations also remains a challenge. In this presentation, the authors present a novel framework, based on multi-axis additive manufacturing (AM), where the orientation and placement of each deposition path (e.g., composite tow) is determined through a custom topology and toolpath optimization (TTO) workflow. A custom topology and orientation optimization algorithm determines material distribution and orientation (in 3D) relative to the input load cases, aligns material depositions to those optimized directions, and orders the deposition paths for collision-free multi-axis manufacturing. The resulting toolpath is then fabricated on a 6 degree-of-freedom industrial robotic arm, which allows material depositions in any direction (e.g., outside of the XY-plane). The manufacturing-aware generative design technique also ensures that the geometry and toolpath are achievable (i.e., printable without collisions) on any user-specified multi-axis deposition platform. As a result, the framework is scalable to any tow width or tool head size (e.g., small tow widths for areas of high curvature or large tow widths for faster deposition rates). This integration of the design and manufacturing phases of part fabrication specifically aligns and distributes the composite material to maximize part performance. When compared to conventional XY-planar toolpaths, TTO resulted in an 82.8% improvement in the mechanical efficiency of a multi-axis tensile load case using a commodity, short-chopped carbon fiber thermoplastic; with a continuously reinforced or otherwise highly anisotropic material, this degree of improvement is expected to further increase.