Continuous Fiber Angle Topology Optimization for Polymer Fused Filament Fabrication

Mechanical properties of parts produced with the Fused Filament Fabrication (FFF) process are known to be dependent on the printed bead direction, especially when short carbon fiber reinforcement is added to the filament. Given that many FFF filament suppliers now offer carbon-fiber filled products, a unique opportunity emerges in the design of polymer composite FFF parts since bead and fiber direction can potentially be prescribed to give the best structural performance. As FFF moves from a technology for rapid prototyping and the hobbyist to a viable additive manufacturing method, it is important to also have a design tool that takes advantage of the opportunities that present themselves when polymer composites are employed. This paper presents a topology optimization method for continuous fiber angle optimization approach (CFAO), which computes optimal material distribution (as in the well known SIMP method) in addition to a preferred fiber angle direction by minimizing compliance of statically loaded structures. Our computed results show the effects of variable orientation angle on fiber reinforced microstructure for the topology of two-dimensional FFF parts. Optimal fiber orientations are shown to align with the axis of structural members that form within the structure as expected. Example design problems are solved and then printed on desktop 3D FFF printers using the material distribution results and a simple infill method which approximates the optimal fiber angle results by a contour-parallel deposition strategy. Mechanical stiffness testing of the printed parts show improved results as compared to structures designed without accounting for the direction of the composite structure. Future work includes extension of the method to three dimensional structures for further application.