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Glass Composites
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ScienceDirect Materials Today: Proceedings 4 (2017) 9542–9546
www.materialstoday.com/proceedings
ICEMS 2016
Statistical Optimization of Process Parameters on Mechanical Properties of Abs/Glass Composites Mahesh T S1*, Nandeeshaiah2, M Krishna3 1 2
Dr AIT, Dept.of Mechanical Engg., Bangalore-560056, Karnataka, India
Dr AIT, Dept. of Mechanical Engg., Bangalore-560056, Karnataka, India 3
R V College of Engineering, Dept. of Mechanical Engg.,Bangalore-560059,Karnataka,India
Abstract The objective of the paper was to investigate by statistical analysis, the degradation of mechanical properties due to hygrothermal exposure of the glass fibre-reinforced acrylonitrile butadiene styrene (ABS) composites at different orientations and compositions. The glass reinforced ABS composites were prepared by hot press technique with different orientation sequences such as 0o/90o, 45o/-45o and 30o/60o strand orientations. The specimens of tensile, flexural and impact fatigue tests were exposed to artificial sea water at 50 °C. All the tests were conducted as per ASTM. Design of experiments using Taguchi L18 Array was formulated to examine the influence of parameters on properties degradation in sea water exposure. The taguchi results showed that fibre orientation of 0°/90° and fibre to resin ratio of 40:60 are the most optimal combinations based on their flexural strength (86.6 MPa), UTS (37.8MPa), and impact strength (134.9 J/m). The overall results showed that 0°/90° fibre orientation and 40:60 fibre-to-resin ratio are best combination for high degradation resistance. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International conference on materials research and applications2016. Keywords: ABS; Glass Fiber; Taguchi; Mechanical Properties; ANOVA ____________________________________________________________________________________________________________________ * Corresponding author. Tel/fax.: +91-94486-70213 E-mail:[email protected].
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Recent Trends in Engineering and Material Sciences (ICEMS2016).
Mahesh T S / Materials Today: Proceedings 4 (2017) 9542–9546
9543
1. Introduction ABS has found its way into diverse fields of engineering, ranging from automobile to off-offshore drilling stations to toys. Addition of glass fibre-reinforced composites has much higher strength than neat ABS materials. In this direction, many researchers investigated reasons for improving mechanical properties. Addition of glass along with clay increases the toughness of ABS composites [1]. Using ABS/PC blends gives better tensile and flexural properties than neat ABS; these properties can be further enhanced by the addition of Kevlar fibres as reinforcement [2]. The tensile properties of ABS can also be improved in the form of hybrid composites of short glass fibre/calcite fibre reinforced ABS [3]. In case of particle reinforced ABS composites, size of the particles affects the mechanical properties; micron-sized calcium carbonate improved the modulus but lowered tensile and impact strength, whereas, nano-sized calcium carbonate showed increase in impact properties along with modulus in a study by L Jiang et al. [4]. Addition of short glass fibre to neat ABS lowers the fracture toughness, whereas, addition of short glass fibres to calcite-filled ABS improves the fracture toughness [5]. When used in marine applications, it is essential that composites retain their mechanical properties and do not degrade when immersed in sea water for many years. Ageing of polymer composites by water soaking, weathering and fungal decay techniques degrades the composite’s surface resulting in increased moisture sorption [6]. S M Sapuan et al.[7] conducted soil burial test on thermoplastic polyurethane/kenaf fibre composites and noticed a drop in tensile strength of the composites whereas flexural properties showed no significant changes [8]. Although most of authors have worked on various properties of ABS composites, but no previous study records have been found on the moisture diffusion and its effect on the mechanical properties of ABS/glass composites. The objective of the work, apparently the first on moisture ageing of ABS composites, is concentrated on studying mechanical properties of ABS of /glass composites exposed to artificial sea water at constant temperature 50 °C for a period of 90 days and optimizing the process parameters using statistical tools like Taguchi analysis, ANOVA and Grey relational analysis. 2. Experimental studies Compression molding technique was used for the fabrication of glass fibre reinforced ABS composite laminates. The moving platens of the hot press were heated to a temperature of 180 °C, general grade ABS and E-glass fibres were used as charge during the fabrication. ABS granules and glass fibre sheets were taken in pre-determined weight ratios. A metallic mould of dimension 300 × 300 mm2 was placed on the bottom platen, a layer of ABS granules was laid inside the mould followed by a layer glass fibre sheets in alternate layers. Then the top platen was kept in place and both the platens were gradually heated to a temperature of 180oC and held at that temperature for about 3 hours. Then, the mould was allowed to cool down to room temperature during which curing of the composites occurs. The obtained 300 × 300 mm2 sheet of composite was cut to the required dimensions by water jet machining process. The test specimen were first prepared in the form of sheets and then cut to the ASTM standards for tensile test (ASTMD638), impact test (ASTM-D256), and flexural test (ASTM-D790)standards. Artificial sea water was prepared as per ASTM D1141 standard in a temperature controlled tank. 260 litres of distilled water was utilised for preparing
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Mahesh T S / Materials Today: Proceedings 4 (2017) 9542–9546
artificial sea water. Precisely weighed quantities of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate and sodium carbonate were added to the distilled water. Design of Experiment (DOE) was performed using mixed level Taguchi orthogonal array in Minitab V16 software. Three factors were considered for the DOE, namely, Period of immersion in artificial sea water with 6 levels (15, 30, 45, 60, 75 and 90 days), fibre-to-resin ratio with 3 levels (60:40, 50:50 and 40:60) and fibre orientation with 3 levels (0o/90o, 45o/45o and 30o/60o). The orthogonal array is shown in Table 1. The flexural tests were performed on the Kalpak Universal testing machine of 10ton capacity. The tests were performed at a strain rate of 1 mm/sec with a gauge length of 40mm. Tensile tests were also performed on the same Table 1. Taguchi orthogonal array Experiment number
Days
F:R ratio
1
15
40:60
Fibre orientation, deg 0/90
2
15
50:50
30/60
3
15
60:40
45/45
4
30
40:60
0/90
5
30
50:50
30/60
6
30
60:40
45/45
7
45
60:40
0/90
8
45
40:60
30/60
9
45
50:50
45/45
10
60
50:50
0/90
11
60
60:40
30/60
12
60
40:60
45/45
13
75
40:60
30/60
14
75
50:50
45/45
15
75
60:40
0/90
16
90
40:60
45/45
17
90
50:50
0/90
18
90
60:40
30/60
Kalpak Universal testing machine of 10 Ton capacity at a strain rate of 1.5 m/sec. A gauge length of 105 mm was used. In this test the maximum load carrying capacity of the composite specimen under tension was determined. Izod impact tests were performed on an impact testing machine with Unnotched test specimens were used for the tests. This test determines the amount of energy consumed by the specimen for initiating and propagating a crack in terms of Joules per unit thickness.
Mahesh T S / Materials Today: Proceedings 4 (2017) 9542–9546
9545
3. Results and Discussion The mean of means flexural strength of ABS/glass composites as shown in Fig. 1 as a function of days, F:R ratio and fiber orientation. The Fig.1 indicate maximum strength for specimen with 40:60 fibre-to-resin ratio with 0o/90o fibre orientation. Also, longer the exposure to seawater more is the reduction in the strength of the composite material. It can be observed that the flexural strength shows a continuously decreasing trend with increase in the period of immersion of composite specimen in the artificial sea water. A decreasing trend for flexural strength is seen for the increasing fibre-to-resin ratio. And the fibre orientation of 0o/90o exhibits highest flexural strength followed by 30o/60o and 45o/45o. The following mean of means of UTS shown in Fig. 2, indicate that maximum strength is shown by composite specimen with 40:60 fibre to resin ratio, 0o/90o fibre orientation and 15 days of exposure to sea water. Fig. 2 shows mean of means plots for different factors for ultimate tensile strength. It can be observed that inter laminar shear stress shows a continuously decreasing trend with increase in the period of immersion of composite specimen in the artificial sea water. A downward trend can be concluded for the increasing fibre-to-resin ratio from the above plot. And the fibre orientation of 0o/90o exhibit highest ultimate tensile strength followed by 30o/60o and 45o/45o. Days
Days
F:R rat io
F:R rat io
34 32
65 60 55 50 15
30
45
60
75
90
40;60
50;50
60;40
Fiber orientat ion
70 65
Mean of Means for UTS
Mean of Means for Flexural strength
70
30 28 15
30
45 60 Fiber orientat ion
75
90
40;60
50;50
60;40
34 32 30
60
28
55
0/90
50 0/90
30/60
30/60
45/45
45/45
Fig. 1 Mean of means for Flexural strength of ABS/glass composites
Fig. 2 Mean of means for ultimate tensile strength of ABS/glass composites
The mean of means impact strength as shown in Fig. 3, indicate that the composites with 40:60 fibre-to-resin ratio along with 0o/90o fibre orientation and least period of immersion in sea water (15 days) exhibits maximum impact strength. Fig. 3 shows mean of means plots for different factors for impact strength. It can be observed that impact strength shows a continuously decreasing trend with increase in the period of immersion of composite specimen in the artificial sea water. Significantly decreasing trend can be seen for the increasing fibre-to-resin ratio from the above plot. And the fibre orientation of 0o/90o exhibits highest impact strength followed by 30o/60o and 45o/45o. The moisture attacks the glass fiber along surface and forms hydroxides which lead degrading the free silica structure. The ABS protects the degradation of silica and avoids further degradation. This indicates that most of the damage mechanisms initiated by sea water exposure are at the interface rather than merely at the fiber level [9]. The quantity of leached organic materials is very less in ABS based composites and they are highly stable in the seawater environment. Analysis of variance shows F-ratio is highest for fibre orientation with a contribution of 23.12%,
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Mahesh T S / Materials Today: Proceedings 4 (2017) 9542–9546
45.19% and 23.14%, making it the most significant factor for flexural, tensile and impact respectively followed by fibre to resin ratio and period of immersion in artificial sea water [10].
Days
Mean of Means for Impact strength
110
F:R rat io
100 90 80 15
30
45
60
75
90
40;60
50;50
60;40
Fiber orient at ion
110 100 90 80 0/90
30/60
45/45
Fig. 3 Mean of means for impact strength of ABS/glass composites 4. Conclusion •
The mechanical properties of the ABS/ glass composites show a downward trend with increased exposure to the artificial sea water.
•
The Taguchi analysis results showed fibre orientation of 0o/90o and fibre-to-resin ratio of 40:60 are the most optimal combination based on their flexural strength (86.6 MPa), UTS (37.8MPa) and impact strength (134.9 J/m.
•
From ANOVA it was found that fibre orientation (23.12%) for flexural strength, fibre orientation (23.15%) for impact strength, period of immersion (45.18%) for ultimate tensile strength, with level of confidence of 95%.
References [1]
Basurto, F.C., García-López, D., Villarreal-Bastardo, N., Merino, J.C., Pastor, J.M., Composites:Part B, vol.47, 2013, pp. 42-47. [2] Sarawut Rimdusit, Parkpoom Lorjia, Kuljira Sujirote and Sunan Tiptipakorn, Engineering Journal, vol 16, 2012, pp. 57-66. [3] Shao-Yun Fu and Bernd Lauke, Composites: PartA, vol. 29A, 1998, pp. 575-583. [4] Jiang, L., Lama, Y.C., Tam, K.C., Chua, T.H., Sim, G.W., Ang, L.S., vol. 46, 2005, pp. 243-252. [5] Shao-Yun Fu and Bernd Lauke, Composites: Part A, vol. 29A, 1998, pp. 631-641. [6] Kristofer Segerholm, B., Rebecca E Ibach, Magnus E P Walinder, BioResources, vol.7, (1), 2012, pp. 1283-1293. [7] Sapuan, S.M., Fei-ling Pua, El-Shekeil, Y.A., Faris M. AL-Oqla, Materials and Design, vol. 50, 2013, pp. 467-470. [8] Ben Difallah, B., Kharrat, M., Dammaka, M., Monteil, G., Materials and Design, vol. 34, 2012, pp. 782787. [9] Xi-Qiang Liu, Wei Yang , Bang-Hu Xie, Ming-Bo Yang, “Materials and Design, vol. 34, 2012, pp. 355362. [10] Naoya Tsuchikura, Michael C. Faudree and Yoshitake Nishi, Materials Transactions, vol. 54, (3), 2013, pp. 371-379.
ScienceDirect Materials Today: Proceedings 4 (2017) 9542–9546
www.materialstoday.com/proceedings
ICEMS 2016
Statistical Optimization of Process Parameters on Mechanical Properties of Abs/Glass Composites Mahesh T S1*, Nandeeshaiah2, M Krishna3 1 2
Dr AIT, Dept.of Mechanical Engg., Bangalore-560056, Karnataka, India
Dr AIT, Dept. of Mechanical Engg., Bangalore-560056, Karnataka, India 3
R V College of Engineering, Dept. of Mechanical Engg.,Bangalore-560059,Karnataka,India
Abstract The objective of the paper was to investigate by statistical analysis, the degradation of mechanical properties due to hygrothermal exposure of the glass fibre-reinforced acrylonitrile butadiene styrene (ABS) composites at different orientations and compositions. The glass reinforced ABS composites were prepared by hot press technique with different orientation sequences such as 0o/90o, 45o/-45o and 30o/60o strand orientations. The specimens of tensile, flexural and impact fatigue tests were exposed to artificial sea water at 50 °C. All the tests were conducted as per ASTM. Design of experiments using Taguchi L18 Array was formulated to examine the influence of parameters on properties degradation in sea water exposure. The taguchi results showed that fibre orientation of 0°/90° and fibre to resin ratio of 40:60 are the most optimal combinations based on their flexural strength (86.6 MPa), UTS (37.8MPa), and impact strength (134.9 J/m). The overall results showed that 0°/90° fibre orientation and 40:60 fibre-to-resin ratio are best combination for high degradation resistance. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International conference on materials research and applications2016. Keywords: ABS; Glass Fiber; Taguchi; Mechanical Properties; ANOVA ____________________________________________________________________________________________________________________ * Corresponding author. Tel/fax.: +91-94486-70213 E-mail:[email protected].
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Recent Trends in Engineering and Material Sciences (ICEMS2016).
Mahesh T S / Materials Today: Proceedings 4 (2017) 9542–9546
9543
1. Introduction ABS has found its way into diverse fields of engineering, ranging from automobile to off-offshore drilling stations to toys. Addition of glass fibre-reinforced composites has much higher strength than neat ABS materials. In this direction, many researchers investigated reasons for improving mechanical properties. Addition of glass along with clay increases the toughness of ABS composites [1]. Using ABS/PC blends gives better tensile and flexural properties than neat ABS; these properties can be further enhanced by the addition of Kevlar fibres as reinforcement [2]. The tensile properties of ABS can also be improved in the form of hybrid composites of short glass fibre/calcite fibre reinforced ABS [3]. In case of particle reinforced ABS composites, size of the particles affects the mechanical properties; micron-sized calcium carbonate improved the modulus but lowered tensile and impact strength, whereas, nano-sized calcium carbonate showed increase in impact properties along with modulus in a study by L Jiang et al. [4]. Addition of short glass fibre to neat ABS lowers the fracture toughness, whereas, addition of short glass fibres to calcite-filled ABS improves the fracture toughness [5]. When used in marine applications, it is essential that composites retain their mechanical properties and do not degrade when immersed in sea water for many years. Ageing of polymer composites by water soaking, weathering and fungal decay techniques degrades the composite’s surface resulting in increased moisture sorption [6]. S M Sapuan et al.[7] conducted soil burial test on thermoplastic polyurethane/kenaf fibre composites and noticed a drop in tensile strength of the composites whereas flexural properties showed no significant changes [8]. Although most of authors have worked on various properties of ABS composites, but no previous study records have been found on the moisture diffusion and its effect on the mechanical properties of ABS/glass composites. The objective of the work, apparently the first on moisture ageing of ABS composites, is concentrated on studying mechanical properties of ABS of /glass composites exposed to artificial sea water at constant temperature 50 °C for a period of 90 days and optimizing the process parameters using statistical tools like Taguchi analysis, ANOVA and Grey relational analysis. 2. Experimental studies Compression molding technique was used for the fabrication of glass fibre reinforced ABS composite laminates. The moving platens of the hot press were heated to a temperature of 180 °C, general grade ABS and E-glass fibres were used as charge during the fabrication. ABS granules and glass fibre sheets were taken in pre-determined weight ratios. A metallic mould of dimension 300 × 300 mm2 was placed on the bottom platen, a layer of ABS granules was laid inside the mould followed by a layer glass fibre sheets in alternate layers. Then the top platen was kept in place and both the platens were gradually heated to a temperature of 180oC and held at that temperature for about 3 hours. Then, the mould was allowed to cool down to room temperature during which curing of the composites occurs. The obtained 300 × 300 mm2 sheet of composite was cut to the required dimensions by water jet machining process. The test specimen were first prepared in the form of sheets and then cut to the ASTM standards for tensile test (ASTMD638), impact test (ASTM-D256), and flexural test (ASTM-D790)standards. Artificial sea water was prepared as per ASTM D1141 standard in a temperature controlled tank. 260 litres of distilled water was utilised for preparing
9544
Mahesh T S / Materials Today: Proceedings 4 (2017) 9542–9546
artificial sea water. Precisely weighed quantities of sodium chloride, calcium chloride, magnesium chloride, sodium bicarbonate and sodium carbonate were added to the distilled water. Design of Experiment (DOE) was performed using mixed level Taguchi orthogonal array in Minitab V16 software. Three factors were considered for the DOE, namely, Period of immersion in artificial sea water with 6 levels (15, 30, 45, 60, 75 and 90 days), fibre-to-resin ratio with 3 levels (60:40, 50:50 and 40:60) and fibre orientation with 3 levels (0o/90o, 45o/45o and 30o/60o). The orthogonal array is shown in Table 1. The flexural tests were performed on the Kalpak Universal testing machine of 10ton capacity. The tests were performed at a strain rate of 1 mm/sec with a gauge length of 40mm. Tensile tests were also performed on the same Table 1. Taguchi orthogonal array Experiment number
Days
F:R ratio
1
15
40:60
Fibre orientation, deg 0/90
2
15
50:50
30/60
3
15
60:40
45/45
4
30
40:60
0/90
5
30
50:50
30/60
6
30
60:40
45/45
7
45
60:40
0/90
8
45
40:60
30/60
9
45
50:50
45/45
10
60
50:50
0/90
11
60
60:40
30/60
12
60
40:60
45/45
13
75
40:60
30/60
14
75
50:50
45/45
15
75
60:40
0/90
16
90
40:60
45/45
17
90
50:50
0/90
18
90
60:40
30/60
Kalpak Universal testing machine of 10 Ton capacity at a strain rate of 1.5 m/sec. A gauge length of 105 mm was used. In this test the maximum load carrying capacity of the composite specimen under tension was determined. Izod impact tests were performed on an impact testing machine with Unnotched test specimens were used for the tests. This test determines the amount of energy consumed by the specimen for initiating and propagating a crack in terms of Joules per unit thickness.
Mahesh T S / Materials Today: Proceedings 4 (2017) 9542–9546
9545
3. Results and Discussion The mean of means flexural strength of ABS/glass composites as shown in Fig. 1 as a function of days, F:R ratio and fiber orientation. The Fig.1 indicate maximum strength for specimen with 40:60 fibre-to-resin ratio with 0o/90o fibre orientation. Also, longer the exposure to seawater more is the reduction in the strength of the composite material. It can be observed that the flexural strength shows a continuously decreasing trend with increase in the period of immersion of composite specimen in the artificial sea water. A decreasing trend for flexural strength is seen for the increasing fibre-to-resin ratio. And the fibre orientation of 0o/90o exhibits highest flexural strength followed by 30o/60o and 45o/45o. The following mean of means of UTS shown in Fig. 2, indicate that maximum strength is shown by composite specimen with 40:60 fibre to resin ratio, 0o/90o fibre orientation and 15 days of exposure to sea water. Fig. 2 shows mean of means plots for different factors for ultimate tensile strength. It can be observed that inter laminar shear stress shows a continuously decreasing trend with increase in the period of immersion of composite specimen in the artificial sea water. A downward trend can be concluded for the increasing fibre-to-resin ratio from the above plot. And the fibre orientation of 0o/90o exhibit highest ultimate tensile strength followed by 30o/60o and 45o/45o. Days
Days
F:R rat io
F:R rat io
34 32
65 60 55 50 15
30
45
60
75
90
40;60
50;50
60;40
Fiber orientat ion
70 65
Mean of Means for UTS
Mean of Means for Flexural strength
70
30 28 15
30
45 60 Fiber orientat ion
75
90
40;60
50;50
60;40
34 32 30
60
28
55
0/90
50 0/90
30/60
30/60
45/45
45/45
Fig. 1 Mean of means for Flexural strength of ABS/glass composites
Fig. 2 Mean of means for ultimate tensile strength of ABS/glass composites
The mean of means impact strength as shown in Fig. 3, indicate that the composites with 40:60 fibre-to-resin ratio along with 0o/90o fibre orientation and least period of immersion in sea water (15 days) exhibits maximum impact strength. Fig. 3 shows mean of means plots for different factors for impact strength. It can be observed that impact strength shows a continuously decreasing trend with increase in the period of immersion of composite specimen in the artificial sea water. Significantly decreasing trend can be seen for the increasing fibre-to-resin ratio from the above plot. And the fibre orientation of 0o/90o exhibits highest impact strength followed by 30o/60o and 45o/45o. The moisture attacks the glass fiber along surface and forms hydroxides which lead degrading the free silica structure. The ABS protects the degradation of silica and avoids further degradation. This indicates that most of the damage mechanisms initiated by sea water exposure are at the interface rather than merely at the fiber level [9]. The quantity of leached organic materials is very less in ABS based composites and they are highly stable in the seawater environment. Analysis of variance shows F-ratio is highest for fibre orientation with a contribution of 23.12%,
9546
Mahesh T S / Materials Today: Proceedings 4 (2017) 9542–9546
45.19% and 23.14%, making it the most significant factor for flexural, tensile and impact respectively followed by fibre to resin ratio and period of immersion in artificial sea water [10].
Days
Mean of Means for Impact strength
110
F:R rat io
100 90 80 15
30
45
60
75
90
40;60
50;50
60;40
Fiber orient at ion
110 100 90 80 0/90
30/60
45/45
Fig. 3 Mean of means for impact strength of ABS/glass composites 4. Conclusion •
The mechanical properties of the ABS/ glass composites show a downward trend with increased exposure to the artificial sea water.
•
The Taguchi analysis results showed fibre orientation of 0o/90o and fibre-to-resin ratio of 40:60 are the most optimal combination based on their flexural strength (86.6 MPa), UTS (37.8MPa) and impact strength (134.9 J/m.
•
From ANOVA it was found that fibre orientation (23.12%) for flexural strength, fibre orientation (23.15%) for impact strength, period of immersion (45.18%) for ultimate tensile strength, with level of confidence of 95%.
References [1]
Basurto, F.C., García-López, D., Villarreal-Bastardo, N., Merino, J.C., Pastor, J.M., Composites:Part B, vol.47, 2013, pp. 42-47. [2] Sarawut Rimdusit, Parkpoom Lorjia, Kuljira Sujirote and Sunan Tiptipakorn, Engineering Journal, vol 16, 2012, pp. 57-66. [3] Shao-Yun Fu and Bernd Lauke, Composites: PartA, vol. 29A, 1998, pp. 575-583. [4] Jiang, L., Lama, Y.C., Tam, K.C., Chua, T.H., Sim, G.W., Ang, L.S., vol. 46, 2005, pp. 243-252. [5] Shao-Yun Fu and Bernd Lauke, Composites: Part A, vol. 29A, 1998, pp. 631-641. [6] Kristofer Segerholm, B., Rebecca E Ibach, Magnus E P Walinder, BioResources, vol.7, (1), 2012, pp. 1283-1293. [7] Sapuan, S.M., Fei-ling Pua, El-Shekeil, Y.A., Faris M. AL-Oqla, Materials and Design, vol. 50, 2013, pp. 467-470. [8] Ben Difallah, B., Kharrat, M., Dammaka, M., Monteil, G., Materials and Design, vol. 34, 2012, pp. 782787. [9] Xi-Qiang Liu, Wei Yang , Bang-Hu Xie, Ming-Bo Yang, “Materials and Design, vol. 34, 2012, pp. 355362. [10] Naoya Tsuchikura, Michael C. Faudree and Yoshitake Nishi, Materials Transactions, vol. 54, (3), 2013, pp. 371-379.