Evaluation of dimensional accuracy and mechanical behavior of 3D printed reinforced polyamide parts

Evaluation of dimensional accuracy and mechanical behavior of 3D printed reinforced polyamide parts

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ScienceDirect

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2019) 000–000

ScienceDirect

www.elsevier.com/locate/procedia

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2019) 000–000

ScienceDirect

www.elsevier.com/locate/procedia

Procedia Structural Integrity 19 (2019) 433–441

Fatigue Design 2019

Evaluation of dimensional accuracy and mechanical behavior of 3D Fatigue Design 2019 printed reinforced polyamide parts Evaluation of dimensional accuracy and mechanical behavior of 3D Aissa Ouballoucha,*, Rachid El alaijib, Said Ettaqia, Mohammed Sallaoua, printed reinforced polyamide parts Aboubakr Bouayada, Larbi Lasria Aissa Ouballouch *, Rachid El alaijib, Said Ettaqia, Mohammed Sallaoua, a,

a

Moulay Ismail University, ENSAM, Marjane 2,B.P. 15290 Al-Mansor,Meknes 50000, Morocco Abdelmalek Essaadi University, ENSA, Road Ziaten Km 10, Tangier aPrincipale , BP: 1818a - Tangier., Tangier 90060, Morocco

b

Aboubakr Bouayad , Larbi Lasri

a

Moulay Ismail University, ENSAM, Marjane 2,B.P. 15290 Al-Mansor,Meknes 50000, Morocco Abdelmalek Essaadi University, ENSA, Road Ziaten Km 10, Tangier Principale , BP: 1818 - Tangier., Tangier 90060, Morocco

b

Abstract

This paper aims to evaluate the mechanical behavior, dimensional accuracy and total cost of fused deposition Abstract modeling (FDM) produced reinforced polyamide (RPA) parts; glass reinforced PA and Kevlar reinforced PA. First of all, the standard specimens are printed by varying three parameters, namely the layer thickness, the print speed and the extrusion temperature. Then, the weightbehavior, and maindimensional dimensions accuracy of the obtained samples measured before This paper aims to evaluate the mechanical and total cost are of fused deposition the mechanical by tensile test. The results showed the effect PA of extrusion temperature modeling (FDM)characterization produced reinforced polyamide (RPA) parts; glass reinforced and Kevlar reinforced and PA. layer First thickness materialspecimens propertiesare is more significant thanthree the impact of print speed.the The influence of evaluated of all, theon standard printed by varying parameters, namely layer thickness, the printfactors speed on the accuracy and total is also Overall,ofthis investigation showed the and thedimensional extrusion temperature. Then, thecost weight and observed. main dimensions theexperimental obtained samples are measured before advantage of reinforcement in enhancing mechanical performance (tensile fatigue properties) andand lead to the mechanical characterization by tensile test. The results showed the effectand of extrusion temperature layer improving thematerial knowledge about is geometrical tolerance ofthe FDM printed reinforced components. thickness on properties more significant than impact of print speed.polymer The influence of evaluated factors on the dimensional accuracy and total cost is also observed. Overall, this experimental investigation showed the advantage of reinforcement in enhancing mechanical performance (tensile and fatigue properties) and lead to improving the knowledge about geometrical tolerance of FDM printed reinforced polymer components. © 2019 The Authors. Published by Elsevier B.V. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. Peer-review under responsibility of the Fatigue Design 2019 Organizers.

Keywords: Fused deposition modeling; polyamide(PA); dimensional accuracy; mechanical behavior; tensile test, fatigue © 2019 The Authors. Published by reinforced Elsevier B.V.

Peer-review under responsibility of the Fatigue Design 2019 Organizers.

Keywords: Fused deposition modeling; reinforced polyamide(PA); dimensional accuracy; mechanical behavior; tensile test, fatigue

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers.

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 10.1016/j.prostr.2019.12.047

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Aissa Ouballouch et al. / Procedia Structural Integrity 19 (2019) 433–441 Aissa Ouballouch et al./ Structural Integrity Procedia 00 (2019) 000–000

1. Introduction Additive manufacturing (AM) refers to a collective advance manufacturing technologies. It is a process of joining materials to make objects from a 3D model data, usually layer by layer (ASTM F2792 - 12 Standard Terminology for Additive Manufacturing Technologies, no date)., which is invented by(‘Apparatus for production of threedimensional objects by stereolithography’, 1984) Charles Hull et al. in 80s. Various methods for polymer fabrication have been developed and drive from rapid prototyping to rapid manufacturing. Among these AM technologies streolithography (SLA), selective laser sintering (SLS) and fused deposition modeling (FDM) that uses polymer filaments (Dudek, 2013). The latter is the most widespread utilized system for plastics AM manufacture because of its relative low cost, low material waste and ease of use (Chua, Leong and Lim, 2003). The FDM process enables to utilize different polymer filaments such as neat feedstock, materials reinforced by chopped or continuous fibers. FDM machines work by controlled extrusion of polymer filaments. In detail, filaments melt into a semi-liquid state at nozzle and are extruded layer by layer onto a build stage where layers are fused together and solidify forming final parts. Basically, the quality of printed parts depends on post processing and varying of printing parameters like layer thickness, extrusion temperature, print speed etc. The influences of these processing parameters have been discussed by many authors in the literature. Although, few studies discuss the overall influence of the processing parameters such dimensional accuracy, mechanical properties and total cost. A study focused on the effect of printing conditions on the mechanical properties and dimensional accuracy was carried out by (Alafaghani et al., 2017) Ala aldin Alafghani et al. This work showed that the dimensional accuracy of PLA parts is affected by building direction, extrusion temperature and layer thickness more than infill percent, infill pattern and printing speed. And the mechanical properties are influenced significantly by building direction, extrusion temperature and layer thickness and less affected by infill patterns for high infill percents and printing speed. Some fluctuation was observed. The aim of this paper is to improve the knowledge about the overall effect of printing parameters in terms of tensile and fatigue properties, dimensional accuracy and total cost. Our study focuses on the reinforced PA parts. Chopped glass fibers and short Kevlar fibers were used in printing of polymer composites. The following sections present the experimental details and results discussion. 2. Experimental 2.1. Materials Reinforced Nylon (polyamide) filaments were supplied by CoreXtrusion Group (COREXTRUSION – Spécialiste de l’extrusion de filaments 3D sur mesure, 2019) . They are glass reinforced polyamide (GRPA) with 15% of short glass fiber and Kevlar reinforced polyamide (KRPA) with the same percent (15%) of chopped kevlar fiber. They are provided in the market by their commercial name TECHStrongTM and TECHArmedTM respectively. These both filaments have a diameter of 1.75mm. Their data sheet and detailed information are accessible and can be consulted via (COREXTRUSION – Spécialiste de l’extrusion de filaments 3D sur mesure, 2019) 2.2. The 3D Volumic 3D printer Figure 1 shows a photopraph of the 3D Volumic 3D printer (Imprimante 3D Professionnelle | VOLUMIC 3D, no date), more specifically Stream 30 Pro type from which test specimens were manufactured additively. The printing process is based on using one print head as the feedstock is formed by reinforced filaments containing chopped fibers. The design of the FDM 3D machine presents some interesting advantages: end of material detection, semiauto calibration, protection to overheating and enabling the printing with most of plastic filaments PLA, ABS, PA including reinforced ones… Its overall dimensions are 520x585x465mm.



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Fig. 1. 3D Volumic 3D printer

To study the influence of layer thickness (LT), print speed (PS) and extrusion temperature (ET) on the mechanical performance, dimensional accuracy and total cost, a number of 3 pieces were produced for each sample. The values of processing parameters are listed in Table 1 while the exact processing parameters are tabulated in Table 2. And Figure 2 illustrates the dimensions used to create the studied specimens in accordance with standard ISO 527. Table 1. Values of processing parameters Parameter

Values for GRPA

Values for KRPA

Extrusion temperature

245 °C, 255 °C, 265°C

245°C, 255°C, 265°C

Print speed

50 mm/s, 60 mm/s, 70 mm/s

50 mm/s, 60 mm/s, 70 mm/s

Layer thickness

0.1 mm, 0.15 mm, 0.2 mm

0.1 mm, 0.15 mm, 0.2 mm

Table 2. Sample processing parameters specification Sample

Material

Extrusion temperature

Print speed

Layer thickness

1

GRPA with +-45° orientation

245°C

50 mm/s

0.2 mm

2

245°C

60 mm/s

0.2 mm

3

245°C

70 mm/s

0.2 mm

4

245°C

50 mm/s

0.1 mm

5

245°C

50 mm/s

0.15 mm

6

255°C

50 mm/s

0.2 mm

7

265°C

50 mm/s

0.2 mm

1

245°C

50 mm/s

0.2 mm

2

KRPA with +-45° orientation

245°C

60 mm/s

0.2 mm

3

245°C

70 mm/s

0.2 mm

4

245°C

50 mm/s

0.1 mm

5

245°C

50 mm/s

0.15 mm

6

255°C

50 mm/s

0.2 mm

7

265°C

50 mm/s

0.2 mm

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Aissa Ouballouch et al. / Procedia Structural 19 000–000 (2019) 433–441 Aissa Ouballouch et al./ Structural Integrity ProcediaIntegrity 00 (2019)

Fig. 2. Created specimens, CAD model, dimensions in mm

2.3. Dimensional accuracy and repeatability All the 3D printed samples for both materials were meseasured and compared to created 3D model. In this study, 11 measurements for each specimen were conducted; they included the total length (TL) of the specimen, the width (W), the reduced section width (RSW) and the thickness (T). Figure 3 depicts these dimensions in detail.

Fig. 3. Dimensions specimen and locations

The measuring is ensured by means of a micrometer. The values of each dimension were averaged. 2.4. Characterization equipment , fatigue analysis and total cost Tensile tests were performed by means of a universal testing machine Zwick/Roell Z050. The specimens were held in place utilizing two grids one fixed and the other one moveable and tested at a crosshead speed of 50mm/minute within a room temperature (23°C) as per ISO 527 standard. The machine is shown in Figure 4. For total cost, the measuring of specimen’s weight was done by means of a balance. For each specimen number (run), three samples were prepared to obtain an average value of the measured properties and characteristics such as the ultime tensile strength, real built up time and weight. In our case, the total cost equation is mainly composed by the material cost per g, fabrication cost per minute. The detailed components are illustrated in Equation 1. Total cost [MAD] = (material[g] x material cost per g [MAD]) + (built up time [min] x machine cost [MAD]) (1)

Fig. 4. View of the of the tensile machine used in this study



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3. Results & discussion The 3D Volumic equipment was used to fabricate GRPA and KRPA samples for tensile testing, dimensional accuracy and total cost assessment. The mechanical performance and above-mentioned evaluations of these samples are discussed in this section. 3.1. Dimensional accuracy and repeatability The measurements of specimen dimensions were averaged into a single value for each dimension in each sample. By comparing these measured and averaged values with the design dimensions, the figures below were created using error Equation 2. Error = Measured Value – Design value (2) The following figures and lines discuss the influence of investigated processing parameters on the dimensional accuracy of studied reinforced PA (RPA) specimens. -Effect of print speed: Looking at Figure 5, the impact of print speed on dimensional error of KRPA and GRPA parts is slight. However, there is an exception for length error of GRPA that is significantly affected. The width and reduced width errors represent the highest values while the thickness error is the lowest. Also from this Figure, it can be seen that the errors in all measured dimensions are lower in the case of GRPA material except the length error. This latter has the positive values for both materials.

Dimensional error [mm]

0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 -0,1 -0,2 -0,3 -0,4 -0,5 -0,6 -0,7 -0,8

Length error KRPA Reduced width error KRPA Length error GRPA Reduced width error GRPA Width error KRPA Thickness error KRPA Width error GRPA Thickness error GRPA

50

55

60

65

Print Speed [mm/s]

70

Fig. 5. Dimensional error of RPA as function of print speed

-Effect of extrusion temperature:

Figure 6 shows the evolution of dimensional errors with the variation of extrusion temperature. The first observation is that the lower error of different dimensions is achieved at temperature 245°C. From 255°C and 265 °C, the errors are slightly affected by the extrusion temperature. From Figure 6, length error is significantly affected by the temperature while other dimensions’ errors are less depending on the temperature. Overall, the most of the errors have positive values. In other words, the length reduced as the temperature rises. For other dimensions, they tend to be higher than their values in 3D model.

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Aissa Ouballouch et al./ Structural Integrity ProcediaIntegrity 00 (2019) Aissa Ouballouch et al. / Procedia Structural 19 000–000 (2019) 433–441

Dimensional error [mm]

0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 0,0 -0,1 -0,2 -0,3 -0,4 -0,5 -0,6 -0,7

Length error KRPA Reduced width error KRPA Length error GRPA Reduced width error GRPA Width error KRPA Thickness error KRPA Width error GRPA Thickness error GRPA

245

255

265

Extrusion Temperature [°C]

Fig. 6. Dimensional error of RPA as function of extrusion temperature

-Effect of layer thickness: As can be seen from Figure 7, the thickness of layers affects the dimensional accuracy significantly. Also, the effect of material is observed. The most of the errors keep an upward trend with increasing of layer thickness except thickness errors that have some fluctuation around the value 0.15 mm. That can be explained in what concerns thickness error because T=4 mm is not an integer multiple of 0.15 mm. For almost dimensions errors, there is an upward trend with rising of layer thickness but there are lower values of errors for length and thickness at 0.2 mm, maximum value of slice height.

Dimensional error [mm]

0,65 0,60 0,55 0,50 0,45 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 0,00 -0,05 -0,10 -0,15 -0,20 -0,25 -0,30

Length error KRPA Reduced width error KRPA Length error GRPA Reduced width error GRPA Width error KRPA Thickness error KRPA Width error GRPA Thickness error GRPA

0,1

0,15

Layer Thickness [mm]

0,2

Fig. 7. Dimensional error of RPA as function of layer thickness



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3.2. Tensile testing The average ultimate tensile strength for each sample is shown in Table 3. These results were used to create Figure 8. Table 3. Tensile testing results Sample

Material

Ultimate Tensile Strength

1

GRPA with +-45° (orientation)

24.52 MPa

2

23.67 MPa

3

22.75 MPa

4

21.22 MPa

5

23.54 MPa

6

23.94 MPa

7

26.29 MPa

1

KRPA with +-45° (orientation)

33.65 MPa

2

33.33 MPa

3

37 MPa

4

25.63 MPa

5

39.54 MPa

6

36.48 MPa

7

37.41 MPa

Figure 8-a) shows the variation of tensile strength of reinforced PA parts with altering of extrusion temperature. For both materials, there is increase of ultimate tensile strength with rising of temperature however the impact in case of glass reinforcement is lower than Kevlar reinforcement case. Figure 8-b) depicts the evolution of ultimate tensile strength of studied reinforced PA parts. The tensile strength is affected by the print speed. The variation of GRPA strength has a downward trend while that of KRPA has an upward trend. The influence of printing velocity on these both materials is opposite. From Figure 8-c), it is shown that the evolution of tensile strength for both materials keep increasing with the rising of layer thickness expect at LT= 0.15 mm where the strength represents the highet value for KRPA. This can be intepreted by the fact that at this layer thickness the suitable multiple heat transfer is achieved between consecutive layers and lines. This thickness value yields lower voids and good bonding. However at thickness slice 0.2 mm, the UTS of KRA decreases which may be due to the lower number of interfaces. a)

UTS of Reinforced PA versus extrusion temperature

UTS of Reinforced PA versus print speed

b)

38 36

UTS [MPa]

34

UTS [MPa]

34

34

32

26

26

24

24 22 245

KRPA GRPA

24

22 250

255

260

Extrusion temperature [°C]

265

20

UTS of Reinforced PA versus layer thickness

40

36

36

20

38

UTS [MPa]

38

50

KRPA GRPA

22 55

60

Print speed [mm/s]

65

70

KRPA GRPA

Fig. 8. UTS of RPA as function of processing parameters

0,10

0,15

Layer Thickness [mm]

0,20

c)

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3.3. Total cost For this evaluation, the sample averaged results of the total cost are shown in Table 4. The indicated results were used to create Figure 9. Table 4. Total cost results Sample

Material

Total cost

1

GRPA with +-45° orientation

10.4 MAD

2

10 MAD

3

9.6 MAD

4

11.35 MAD

5

11 MAD

6

10.9 MAD

7

11.3 MAD

1

KRPA with +-45° orientation

8.6 MAD

2

8 MAD

3

7.5 MAD

4

9.3 MAD

5

9 MAD

6

9 MAD

7

9.4 MAD

Looking at Figure 9-a), the total cost of KRPA and GRPA parts keeps a trend decrease with increase of print speed. That is due to reduced deposition time when the printing velocity is higher. As can be seen from Figure 9-b), the total cost of KRPA and GRPA parts has a trend decrease with rising of layer thickness. This evolution can be explained by higher deposition time caused by much layers when the thickness is small. Figure 9-c) illustrates the evolution of total cost of KRPA and GRPA materials in function of extrusion temperature. With increase in temperature the total cost value increases for both materials. Regardless of printing parameter the total cost of GRPA is more than KRPA one. Among reasons of this finding the high GRPA filament price.

11

Total cost of Reinforced PA versus print speed

12,0

Total Cost of Reinforced PA versus layer thickness

50

Total Cost [MAD]

10,5

10,4

10,0

10,0 9,6

9,5

KRPA GRPA

9,0 8,5 60

Print Speed [mm/s]

70

8,0

Total Cost of Reinforced PA versus extrusion temperature

10,8

Total Cost [MAD]

Total cost [MAD] 8

12,0 11,2

11,0

9

b)

11,6

11,5

10

7

a)

KRPA GRPA

0,10

9,2 8,8

0,15

Layer Thickness [mm]

0,20

8,4 8,0

KRPA GRPA

245

Fig. 9. Total cost of RPA as function of processing parameters

250

255

260

Extrusion Temperature [°C]

265

c)

)



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3.4. Fatigue analysis The results of neat PA model and KRPA model with real density are shown in Figure 10. The experimental findings in terms of mechanical properties and density were used to implement the finite element model. The fatigue and safety factor of neat filament are illustrated respectively in Figure 10-c) and 10-d), while those of KRPA ones are depicted in Figure10-a) and 10-b). As can be seen from these pictures, the impact of Kevlar reinforcement on the fatigue properties is observed. a)

b)

c)

d)

Fig. 10. Resulting fatigue properties from FEA

4. Conclusions Chopped glass and Kevlar fibers reinforced nylon composites were fabricated additively by FDM technology. The effect of layer thickness, print speed and extrusion temperature on these reinforced PA samples was investigated, independently in terms of tensile and fatigue properties, dimensional accuracy and total cost. The FDM composites were found to exhibit tensile strengths which were superior to that of neat nylon for Kevlar reinforced PA. Comparing the fiber reinforcing investigated in this study it was found that the nylon composite strength was in the following order: Chopped Kevlar fiber> chopped glass fiber. Dimensional accuracy of KRPA is more affected by the printing parameters than GRPA. Ultimate tensile strength of GRPA is less impacted by the processing parameters than KRPA. Total cost of KRPA and GRPA are affected by the PPs following the same trend. In addition, the fatigue analysis showed the effect of Kevlar reinforcement in enhancing fatigue properties of RPA. A finite element analysis is required to provide a helpful model for understanding numerically the effect of these evaluated processing parameters. References Alafaghani, A. et al. (2017) ‘Experimental Optimization of Fused Deposition Modelling Processing Parameters: A Design-for-Manufacturing Approach’, Procedia Manufacturing. Elsevier B.V., 10, pp. 791–803. doi: 10.1016/j.promfg.2017.07.079. ‘Apparatus for production of three-dimensional objects by stereolithography’ (1984). Available at: https://patents.google.com/patent/US4575330A/en (Accessed: 22 October 2019). ASTM F2792 - 12 Standard Terminology for Additive Manufacturing Technologies, (no date). Available at: https://www.astm.org/DATABASE.CART/HISTORICAL/F2792-12.htm (Accessed: 30 October 2019). Chua, C. K., Leong, K. F. and Lim, C. S. (Chu S. (2003) Rapid prototyping : principles and applications. World Scientific. Available at: https://books.google.se/books/about/Rapid_Prototyping.html?id=dd5ddgDOsGMC&redir_esc=y (Accessed: 30 October 2019). COREXTRUSION – Spécialiste de l’extrusion de filaments 3D sur mesure (no date). Available at: https://www.corextrusion-group.com/ (Accessed: 9 October 2019). Dudek, P. (2013) ‘FDM 3D printing technology in manufacturing composite elements’, Archives of Metallurgy and Materials, 58(4), pp. 1415– 1418. doi: 10.2478/amm-2013-0186. Imprimante 3D Professionnelle | VOLUMIC 3D (no date). Available at: https://www.imprimante-3d-volumic.com/fr/volumic-3d.cfm (Accessed: 22 October 2019).