M.A.Caminero et al 2022a - Revision history

Materiales.Compuestos at 18:16, 1 November 2022

2022-11-01T18:16:39Z

Scipediacontent: Scipediacontent moved page Review 486245807399 to M.A.Caminero et al 2022a

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Scipediacontent moved page Review 486245807399 to M.A.Caminero et al 2022a

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M.A.Caminero^a, J.M.Chacón^b, E. García-Plaza^a, P.J.Núñez..."

2022-03-30T21:56:10Z

Created page with " <div class="center" style="width: auto; margin-left: auto; margin-right: auto;"> M.A.Camineroa, J.M.Chacónb, E. García-Plazaa, P.J.Núñez..."

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 There are no standard test methods for tensile and flexural properties of parts fabricated using FDM. In this work, the ASTM D638 [45] and D790 [46] methods were applied for testing tensile and flexural specimens, respectively. The geometry of the 3D printed specimens were modelled using SolidWorks software, exported as an STL file and imported to the 3D printing software. The geometry of the tensile and flexural specimens are shown in Figure [1].
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 Build orientation has a major role on the structural properties of FDM parts. It refers to how and which direction a sample is placed on the 3D printing build platform. Due to the layered nature of the FDM process, 3D printed materials exhibit anisotropic behaviour that makes structural performance highly dependent on build orientation. The effects of build orientation on mechanical performance of FDM parts have been previously studied [1,4,5,10,38,39] and the highest tensile strength is obtained when the fused filament deposition coincided with the pull direction [6]. However, a range of orientations may be found along this pull direction, which have not been analysed in other studies. In this study, three build orientations were assessed, see Figure 2a : Flat (F) and On-Edge (O), where the fused filament deposition was positioned in the same direction as the pull direction for the tensile case and Upright (U), in which layers were deposited perpendicular to the pull direction.
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-<span style="text-align: center; font-size: 75%;">'''Figure 2. '''Process parameters: a) Build orientation. b) Layer thickness and perimeter raster</span></div>
+<span style="text-align: center; font-size: 75%;">'''Figure 2. '''Process parameters: a) Build orientation. b) Layer thickness and perimeter raster.</span></div>
 One of the most important and controversial parameters to determinate the quality of a part fabricated using FDM is the layer thickness (Lt), see Figure 2b. Rankouhi et al. [6] stated that, although layer thickness has been studied extensively, see for examples References [1,9,11,32,38], it should be further analysed, due to the disparity of results. In this work, different layer thickness values were considered in order to analyse the influence of this parameter. These values were selected according to the Witbox 3D printer range. In comparison, in the case of the Dimension Elite 3D printer, only two layer thickness values were analysed due to restrictions in the selection of this parameter. In both cases, layer thickness was measured in the Z direction.
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 The uniaxial tensile tests were performed following the standard ASTM D638-10 standard [45]. A 50 kN universal electro-mechanical testing machine at a fixed loading rate of 2 mm/min was used for the tensile test, see Figure 3a. Figure 3b shows the set-up of a tensile specimen and test fixture. Strain was measured using a MTS 634.14 high-performance axial extensometer. The experimental data were processed following the recommendations of the previous standard, for the determination of the maximum tensile strength and the tensile Young's modulus. Young's modulus was determined considering the linear part of the stress-strain curve and the slope was estimated by a linear fit. Tensile strength was calculated as a ratio between the maximum load reached during the test and the cross-sectional area.
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 ABS tensile and flexural specimens were fabricated with the industrial 3D printer Dimension Elite for comparative purposes. Due to the limitation of this industrial 3D printer, only a feed rate of 43 mm/s  and two different layer thickness (L<sub>t</sub>=0.18 mm and 0.24 mm) could be selected. A total of 60 ABS specimens were fabricated and tested. Average and standard deviation of the tensile and flexural test results for the ABS samples are shown in Table 2. The results have shown that PLA samples exhibited strength and stiffness values that are about twice the values of ABS samples. However, even if PLA samples were stronger than ABS samples, they were more brittle. Indeed, the deformation at fracture was about 2-4% for the tensile PLA samples and more than 8% for the ABS ones, see Figure 4. PLA offers better thermomechanical characteristics than ABS, having a stronger mechanical resistance and a lower thermal expansion.coefficient. On the other hand, the most important disadvantage of PLA compared  with ABS is the lower durability due to its biodegradability [5].
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 As expected from the tensile test results of Table 3, functional load bearing samples with L<sub>t</sub>=0.06 mm depicted higher mechanical strength compared to samples with L<sub>t</sub>=0.24 mm.
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 |  style="text-align: right;"|<span style="text-align: center; font-size: 75%;">1917-2507 MPa</span>
 |}
 PLA samples were fabricated using a WitBox desktop 3D printer, manufactured by BQ [42]. WitBox is a low cost desktop printer that uses PLA material with a 0.4 mm nozzle size. WitBox can be controlled with any open source software. In this study, Cura software [43] was used to generate G-code files and to command and control all the process parameters. Furthermore, ABS samples were fabricated using the industrial 3D printer Dimension Elite, developed by Stratasys. The Dimension Elite is a high performance industrial printer that uses ABS material, and is controlled by CatalystEX Software [44], a specific software that can modify only a limited number of process parameters.
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 |  style="border-bottom: 2pt solid black;text-align: center;vertical-align: top;"|<span style="text-align: center; font-size: 75%;">758.3 (50.5)</span>
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 ABS tensile and flexural specimens were fabricated with the industrial 3D printer Dimension Elite for comparative purposes. Due to the limitation of this industrial 3D printer, only a feed rate of 43 mm/s  and two different layer thickness (L<sub>t</sub>=0.18 mm and 0.24 mm) could be selected. A total of 60 ABS specimens were fabricated and tested. Average and standard deviation of the tensile and flexural test results for the ABS samples are shown in Table 2. The results have shown that PLA samples exhibited strength and stiffness values that are about twice the values of ABS samples. However, even if PLA samples were stronger than ABS samples, they were more brittle. Indeed, the deformation at fracture was about 2-4% for the tensile PLA samples and more than 8% for the ABS ones, see Figure 4. PLA offers better thermomechanical characteristics than ABS, having a stronger mechanical resistance and a lower thermal expansion.coefficient. On the other hand, the most important disadvantage of PLA compared  with ABS is the lower durability due to its biodegradability [5].

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