Browsing by Subject "convergence zone"

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Effect of Extrudate Swell, Nozzle Shape, and Convergence Zone on Fiber Orientation in Fused Deposition Modeling Nozzle Flow
(University of Texas at Austin, 2015) Heller, B.P.; Smith, D.E.; Jack, D.A.
Recent advances for improving the mechanical properties of materials used in Fused Deposition Modeling (FDM) include the addition of carbon fibers to the filament feedstock. During processing, the flow field within the polymer melt orients the fiber suspension, which is important to quantify since fiber orientation influences mechanical and thermal properties. This paper presents a computational approach for evaluating polymer melt flow and fiber orientation within a FDM nozzle taking into consideration the converging flow in the nozzle, fluid expansion caused by extrudate swell, and nozzle exit shape. Finite elements are used to evaluate the Stoke’s flow in an axisymmetric nozzle and fiber orientation tensors are evaluated along streamlines within the flow using the Fast Exact Closure and Folgar-Tucker isotropic rotary diffusion. Fiber orientation is shown to increase in the shear-dominated flow through the nozzle, however, alignment is found to decrease in the expansion flow of the die swell.