Abstract

Fused Filament Fabrication (FFF) is becoming increasingly important in the automotive industry as it enables the additive manufacturing (AM) of short fiber reinforced plastic components. AM of composites enables load bearing and highly stiff parts for the use in automotive applications (jigs, fixtures, functional prototypes). During the process, molten plastic is deposited as a continuous bead layer by layer onto a print bed until the component is completed. While adding short fibers enhances the mechanical properties of FFF parts, the anisotropic behavior increases since the fibers are aligned during printing in bead direction. This leads to high mechanical properties in bead direction, but only low strength and stiffness remain perpendicular to the bead direction. As the deposition strategy includes part orientation and infill pattern design decisions, it has a significant effect on the part’s resulting structural behavior. The objective of this work was to develop a method that enables the printing of stiffness-optimized parts via FFF with short fiber reinforced materials to increase part perfomance. The anisotropic material behavior was considered during the preparation of the part orientation and infill pattern through a structural FE analysis with an orthotropic material. An energy-based method was used to optimize the local material orientations. Afterwards, the optimized orientations were exported into a slicer programmed with Python and converted into print paths (G-code). As a result, the short fibers in the printed part are optimally aligned for a specific load case. The developed method was used to optimize infill patterns of two geometries with simple and more complex loading conditions. Afterwards, those infill patterns were compared to conventional patterns from common slicers by performing quasi-static tests. The optimized infill showed a significant increase in stiffness. The results enable engineers to prepare load path compliant infill patterns for highly stiff structural parts customized for a specific load case without additional design changes and tooling.