Effects of extrudate swell and nozzle geometry on fiber orientation in Fused Filament Fabrication nozzle flow

Heller, Blake P.; Smith, Douglas E.; Jack, David A.

doi:10.1016/j.addma.2016.06.005

Cited by 118 publications

(126 citation statements)

References 31 publications

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“…We hypothesized that this is caused by radial flow and fusion between adjacent roads. Additionally, the difference between CNT alignment at the intersection between printed roads and within individual roads suggested the importance of a convergence zone within the printer chamber, consistent with a recent FDM simulation study . Lastly, inclusion of 5% CNTs (by weight) increased the Young's modulus of the FDM parts by 30%, but the tensile strength and toughness decreased by 11 and 22%, respectively.…”

Section: Discussionsupporting

confidence: 82%

“…S5), the nozzle is tapered. The converging flow further leads to extensional deformation, which aligns the CNTs more effectively than simple shear flows because of the absence of a rotation component .…”

Section: Resultsmentioning

confidence: 99%

“…For a given volumetric flow rate, the flow velocity increases as the cross‐sectional area decreases. The increase in flow velocity leads to extensional deformations, which further align the fibers at the core .…”

Section: Resultsmentioning

confidence: 99%

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The microstructure and mechanical properties of 3D printed carbon nanotube‐polylactic acid composites

et al. 2017

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This article reports 3D printing of carbon nanotube‐polylactic acid (CNT‐PLA) composites using an extrusion‐based Fused Deposition Modeling (FDM) method. CNTs with an average diameter of 128 nm and an average length of 2.5 μm were first compounded with PLA and extruded into feedstock filaments at 0.5%, 2.5%, and 5% (w/w) CNT loadings. CNT aggregates were observed, but no clogging occurred during printing with a 500‐μm print nozzle. The rheology of the CNT‐PLA samples was characterized to understand the printing‐induced alignment of CNTs along the road axis. Additionally, the effect of printing flow rate was explored for a fixed printing gap and nozzle diameter. Higher flow rates reduced the void fraction in the FDM parts, but unexpectedly resulted in less degree of CNT alignment, which is attributed to radial flow and fusion between adjacent roads. The mechanical properties of the CNT‐PLA tensile test coupons were characterized. Inclusion of CNTs increased the Young's modulus by 30% at 5% CNT loading, but reduced the tensile strength and overall toughness of the FDM parts. Experimental data were compared against the Rule of Mixtures (RoM) model, the Halpin‐Tsai model, and the modified RoM model and were further explained by the void fraction and CNT orientation. POLYM. COMPOS., 39:E1060–E1071, 2018. © 2017 Society of Plastics Engineers

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Section: Discussionsupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

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The microstructure and mechanical properties of 3D printed carbon nanotube‐polylactic acid composites

et al. 2017

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“…Since there are no other beads to constrain the flow, the material moves more in the crossflow direction. The change in orientation through processing is consistent with Heller's and Skrabala's results [16,21], showing that orientation will decrease during the expansion due to die swell occurring after the nozzle. However, the actual flow field is more complex than simple die swell, since the material turns 90° and is deformed as it is deposited.…”

Section: Fiber Orientation Measurementssupporting

confidence: 78%

“…However, any reorientation that occurs, as suggested by these results, is positive for the wall conductivity, as discussed in the following section. Geometric changes to the nozzle could increase this effect; for example, Heller's work suggests that lengthening the land at the nozzle exit could lead to higher perpendicular orientation [16]. Figure 9 shows the thermal diffusivity for 20% vol copper fiber PA6 in the through-plane, wall, and laminate samples.…”

Section: Fiber Orientation Measurementsmentioning

confidence: 99%

Process-Induced Fiber Orientation in Fused Filament Fabrication

et al. 2018

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Abstract:As the applications for additive manufacturing have continued to grow, so too has the range of available materials, with more functional or better performing materials constantly under development. This work characterizes a copper-filled polyamide 6 (PA6) thermoplastic composite designed to enhance the thermal conductivity of fused filament fabrication (FFF) parts, especially for heat transfer applications. The composite was mixed and extruded into filament using twin screw extrusion. Because the fiber orientation within the material governs the thermal conductivity of the material, the orientation was measured in the filament, through the nozzle, and in printed parts using micro-computed tomography. The thermal conductivity of the material was measured and achieved 4.95, 2.38, and 0.75 W/(m·K) at 70 • C in the inflow, crossflow, and thickness directions, respectively. The implications of this anisotropy are discussed using the example of an airto-water crossflow heat exchanger. The lower conductivity in the crossflow direction reduces thermal performance due to the orientation in thin-walled parts.

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Processes, Machines and Materials

2017

From Additive Manufacturing to 3d/4d Printing 1

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Effects of extrudate swell and nozzle geometry on fiber orientation in Fused Filament Fabrication nozzle flow

Cited by 118 publications

References 31 publications

The microstructure and mechanical properties of 3D printed carbon nanotube‐polylactic acid composites

The microstructure and mechanical properties of 3D printed carbon nanotube‐polylactic acid composites

Process-Induced Fiber Orientation in Fused Filament Fabrication

Processes, Machines and Materials

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