Abstract
Mechanical properties of parts produced with polymer deposition additive manufacturing (AM) depend on the print bead direction, particularly when short carbon-fiber reinforcement is added to the polymer feedstock. This offers a unique opportunity in the design of these structures since the AM print path can potentially be defined in a direction that takes advantage of the enhanced stiffness gained in the bead and, therefore, fiber direction. This paper presents a topology optimization approach for continuous fiber angle optimization (CFAO), which computes the best layout and orientation of fiber reinforcement for AM structures. Statically loaded structures are designed for minimum compliance where the adjoint variable method is used to compute design derivatives, and a sensitivity filter is employed to reduce the checkerboard effect. The nature of the layer-by-layer approach in AM is given special consideration in the algorithm presented. Examples are provided to demonstrate the applicability of the method in both two and three dimensions. The solution to our two dimensional problem is then printed with a fused filament fabrication (FFF) desktop printer using the material distribution results and a simple infill method which approximates the optimal fiber angle results using a contour-parallel deposition strategy. Mechanical stiffness testing of the printed parts shows improved results as compared to structures designed without accounting for the direction of the composite structure. Results show that the mechanical properties of the final FFF carbon fiber/polymer composite printed parts are greatly influenced by the print direction, and optimized material orientation tends to align with the imposed force direction to minimize the compliance.
Highlights
Carbon-fiber-filled polymer composites continue to provide unique engineering solutions for lightweight structures in industries such as automotive and aerospace
This paper focuses on the use of short fiber/polymer composites in the fused filament fabrication (FFF) process; the design method presented here is applicable to other additive manufacturing (AM) processes that result in oriented microstructures
Fiber orientation symmetry existed in each layer by comparing the first three layersThis counting the top ato topology the three layers countingapproach from the bottom
Summary
Carbon-fiber-filled polymer composites continue to provide unique engineering solutions for lightweight structures in industries such as automotive and aerospace. It is well understood that the mechanical properties of thermoplastic polymers can be greatly improved by adding short carbon or glass fibers to the polymer matrix, making it possible to produce structures having superior performance with existing tooling. This is true in today’s additive manufacturing (AM) where small-scale three-dimensional (3D) printer filament suppliers offer carbon-fiber-filled products for the fused filament fabrication (FFF) process ( known as fused filament deposition (FDM)). A unique design opportunity emerged for fiber-reinforced polymer composite AM since the direction of the non-isotropic print bead can potentially be designed to give the best overall structural performance. This paper focuses on the use of short fiber/polymer composites in the FFF process; the design method presented here is applicable to other AM processes that result in oriented microstructures
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