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ScienceDirect Materials Today: Proceedings 16 (2019) 800–807

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ICAMMAS17

Effect of MWCNT particles on wear loss in dry sliding wear of PEEK matrix composites D. Kumar a T. Rajmohan a, *

a&b

Sri Chandrasekharendra Saraswathi Viswa Maha Vidyalaya University, Enathur, Kanchipuram – 631561, India

Abstract In present circumstances nano particles reinforced with polymer matrix composites (PMC) are used for plentiful applications. Poly-ether-ether-ketone (PEEK) is enactment thermoplastic which have been used extensively in many engineering applications due their excellent mechanical, thermal electrical properties and wears resistance. Multi Wall Carbon Nano Tubes (MWCNT) reinforced PMCs can improve the properties of matrix material in terms of frictional resistance and tensile strength. In the current research, the wear performance of MWCNT reinforced PEEK matrix composites is examined using the pin-on-disk apparatus under dry condition. The wear parameters such as load, sliding speeds, temperature and wt % MWCNT are considered to evaluate wear loss in the composites. The MWCNT reinforced PEEK matrix composites were prepared by using melt mixing technique. Machining and polishing operations were used to make the pin size of square 8 mm and height 30 mm. Response surface design is engaged to perform the experiments. After wear test the worn out surfaces are studied through scanning electron microscopy. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials, Manufacturing and Applied Sciences. Keywords: Polymer matrix composites; MWCNT; Temperature; Weight loss; SEM; PEEK.

1. Introduction In present scenario nano particles reinforced with polymer is used for numerous applications in particular Polyetheretherkotone (PEEK) have plentiful applications due their outstanding properties. The high-performance PEEK polymer is first primed by Bonner in 1962[1].The wear behavior of PEEK under varying loading is investigated by Vioss and Friedrich[2]. The addition of silica nano particles in PEEK will increase the degree of crytallinity of nano composites[3]. Bijwe.et.al found that Inclusion of PTFE( 0 to 30 wt %) in PEEK will increase the performance of PEEK – Low wear rate 1x10-16 m3/Nm and five times in coefficient of friction[4]. Friction coefficient of functionally graded PEEK surface is less than compositionally graded PEEK and PTFE components and Wear rate of graded PEEK surface improved then the compositionally graded PEEK and PTFE components [5] * Corresponding author. E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials, Manufacturing and Applied Sciences.

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Tribological behaviour of PEEK nano composites in dry and vacuum environment (dry sliding conditions) have very low friction and wear rate [6]. Lai & Chen investigated that Coefficient of thermal expansion and modulus of PEEK nano composite of surface treated with stearic acid have more value of coefficient of thermal expansion then unmodified PEEK [7]. Sliding behaviour of PEEK composite with potassium titanate whiskers under water lubricated condition will increases Strength and Stiffness and decrease in temperature of crystallization of PEEK and wear rate is decreased for the filled composites[8]. Zhong.et al. established that carbon fibre reinforced PEEK matrix composites have exceptional wear resistance due to synergy effect between filler and carbon fibre[9]. Tribological behaviour of PEEK /Poly tetra fluoro ethylene composite reinforced with Pottassium Titanate Whiskers found better tribological properties than those without Pottassium Titanate Whiskers [10]. Kuo et al.[11] have concluded that the addition of nano silica particles improves the peak crystallization times in the PEEK matrix Vail.et.al[12] investigated that wear rates of PTFE-PEEK composites were better than filled composites. Rajmohan et al.[13] have found that glass fibre reinforced PEEK matrix composites have enhanced wear resistance due to formation of platic film on the counterpart at higher levels.The friction coefficient is mainly influenced by sliding distance followed by the temperature[14]. The performance of MWCNT reinforced PEEK under dry sliding conditions is studied under varying load, sliding speed and Varying % of MNCNT developed modeling equations for each response[15]. The best of our literature survey, the reports on the performance of PEEK reinforced with MWCNT is very scarce; it left the scope to the authors to study the wear performance of PEEK composites. In the present investigation, the wear loss of MWCNT reinforced PEEK composites is studied under various dry sliding conditions After wear test, the worn our surfaces are examined using SEM. 2. Experimental 3.1. Materials \used The starting materials such as PEEK (5300 grade) and MWCNT were procured from M/s Gharda Chemicals,Ltd. Panoli, Gujarat, India and M/S US Research Nano materials Inc, USA respectively, The received materials were pre dried out at 125°C for 6 hours earlier to compounding. The composites were primed by using melt mixing technique[16]. The prepared composites are presented in Fig. 1.

Fig.1. Prepared MWCNT reinforced PEEK composites

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3.2. Experimental plan: D-optimal design is employed to conduct the experiments and to analyze the wear loss of PEEK matrix composites. Table 1 shows the design matrix in which speed, load, temperature were varied for three levels, while and wt % MWCNT is varied at two levels. Table 1.Control parameters Parameters

Symbol

Sliding speed m/s Load N Temperature Wt of MWCNT %

S W T M

Numerical Numerical Numerical Categorical

Levels 2 1.82 30 90 1

1 0.63 10 75 0

3 3 50 120

Table 2. Experimental results S. no.

Sliding speed m/s

Load N

Temp deg

Material

Wear loss mm3

1

1.82

30

90

PEEK

4.60384E-06

2

0.63

10

120

PEEK+1% MWCNT

3.15231E-06

3

3

10

75

PEEK

6.43269E-06

4

3

10

90

PEEK+1% MWCNT

3.33774E-06

5

3

50

90

PEEK

0.000005175

6

0.63

50

90

PEEK+1% MWCNT

3.59106E-06

7

3

10

120

PEEK

4.53846E-06

8

0.63

50

120

PEEK

4.89231E-06

9

0.63

10

75

PEEK+1% MWCNT

4.47021E-06

10

3

50

75

PEEK+1% MWCNT

5.63742E-06

11

0.63

10

75

PEEK

5.94231E-06

12

1.82

50

120

PEEK+1% MWCNT

3.82782E-06

13

0.63

50

75

PEEK

6.92308E-06

14

3

30

120

PEEK+1% MWCNT

2.78146E-06

15

1.82

30

75

PEEK+1% MWCNT

5.01656E-06

16

1.82

10

75

PEEK

6.17308E-06

17

0.63

30

75

PEEK

6.43269E-06

18

1.82

10

75

PEEK+1% MWCNT

4.14735E-06

19

1.82

30

75

PEEK

6.66349E-06

20

0.63

10

120

PEEK+1% MWCNT

3.15231E-06

21

3

10

120

PEEK

4.53846E-06

22

3

50

75

PEEK+1% MWCNT

5.63742E-06

23

0.63

50

120

PEEK

4.89231E-06

24

0.63

50

90

PEEK+1% MWCNT

3.59106E-06

The pin on disc machine supplied by M/s Ducom, India is used conduct dry sliding wear tests for the MWCNT reinforced PEEK matrix composites [15], The pin size of diameter 6mm and height 10 mm was prepared by

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machining and then polished. The arrangement of the pin-on-disc wear testing machine is presented in Fig. 2. The pin is supposed stationary against the counter face of 110mm diameter disc made of Stainless steel 316 having hardness HRC 65.The pin is detached and cleaned with acetone for each experiment. The weight loss is calculated by using digital balance having least count of 1mg. The experimental results are shown in Table 2.

Fig. 2. Pin on Disc setup

3. Results and Discussions 3.1. Development of quadratic model for wear loss: Response Surface Methodology (RSM) is significant division of experimental design. RSM design is a cooperative tool for quantification of the correlation between one or more measured responses and the dynamic input factors. The D-optimal design is intended to use with categorical factors as substitute to the general optimal design option. In engineering fields, there is a correlation between the output response of interest ‘y’ and a set of independent input variables {x1, x2, ……… xn}. If, the natures of the correlation between y and x values are known, then, a model can be formulated in the form (2) y f ( x1, x 2 ,... x n )

Where, represents the noise or error observed in the response y. If we denote the expected response be E(y) = f ( x1, x 2 ,... x n ) , then the surface represented by

f ( x1, x 2 ,... x n )

(3)

is called response surface.Usually a second order model is utilized in response surface methodology k

k

i 1

i 1

y 0 i xi ii xi2 ij xi x j i

(4)

j

The coefficients, which should be determined in the second order model, are obtained by the least square method. The unbiased estimator € of the regression coefficient. The quadratic mathematical models for wear loss are developed by using Design Expert® software. In this study, the final quadratic models given in the actual

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D. Kumar and T. Rajmohan / Materials Today: Proceedings 16 (2019) 800–807

terms regarding wear loss (mm3} for PEEK and PEEK+MWCNT composites is presented in Equation 5 and 6 respectively. Wear loss =+7.40921E-006 +3.60606E-007 * Speed +1.91183E-008* Load -1.14838E-008* Temperature +4.57609E-009 * Speed * Load -7.52909E-009 * Speed * Temperature -3.26323E-010 * Load * Temperature -----------(5) Wear loss =+4.63061E-006 +7.13497E-007 * Speed+3.66001E-008* Load-1.16936E-008 *Temperature+ 4.57609E-009 * Speed * Load-7.52909E-009* Speed * Temperature -3.26323E-010* Load * Temperature--------------(6) 3.2. The investigation of the quadratic mathematical model: The mathematical models for wear loss (mm3) and the data are examined statistically by using analysis of variance (ANOVA). ANOVA is used for categorizing the factors that affects the performance measures of quadratic models [13]. In modelling, the goals are used to approximate the variability of the parameters and variability among the error effects. The sum of Square (SS) is the square of the deviation from the grand mean of the response and mean Square (MS) is the ratio of sum of squares to the number of degrees of freedom. F-value is an index used to check the adequacy of the model, which is the ratio of mean squares of the regression to the error terms [13]. The test for significance and the test for lack-of-fit are accomplished to analyse the adequacy of the established model as shown in Table 3. The values of “F-value”, the “Prob. > F”, R2 and adjusted R2imply are transactions of how fine the model fits the data. These values can help to select the model with the best fit. The value of Adeq precision (AP) in this model, which associates the range of the predicted value at the design point to the average prediction error is well above 15. The value of the ratio is greater than 15, which presents the adequate model discrimination. Moreover the analysis of model validation is carried out using normal probability plot. The normal plots for responses presented in Figure 3 are normally distributed and they be similar to a straight line, which indicate that the developed models are significant.

Design-Expert® Softw are R1

Normal Plot of Residuals

Color points by value of R1: 6.92308E-006

95

Normal % Probability

2.78146E-006

99

90 80 70 50 30 20 10 5 1

-2.10

-1.12

-0.14

0.84

Internally Studentized Residuals

Fig.3. Normal plot of residual for wear loss

1.82

D. Kumar and T. Rajmohan / Materials Today: Proceedings 16 (2019) 800–807

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The wear loss of the PEEK matrix composite can be calculated from Equations presented in 5 and 6. The values of β0 for PEEK and PEEK-MWCNT composites are 7.4 and 4.6 respectively. The value of β0 is the catch of the plane and is a mean response value for all the experiments conducted. The value of β0 depends on the wear parameters and experimental irregularities. It is very perfect from the experimental results and the coefficient β0 of the equations that the wear resistance of PEE+MWCNT is less than that of PEEK. The positive values of the coefficient recommend that the wear loss of the composites increases with the increase in the related variables, whereas the negative values of the coefficients indicates the differing effect [13]. The magnitude of the variables indicates the relative weight of each of these factors. It is observed from Equations 5 & 6 that temperature and wt % of MWCNT has a significant effect on wear loss.

Fig.4. SEM image of MWCNT reinforced PEEK composites : a. 100% PEEK b. PEEK reinforced with 1% MWCNT c. Worn surface of 100% PEEK at low temperature d. Worn surface of PEEK reinforced with 1% MWCNT at low temperature e. . Worn surface of 100% PEEK at high temperature f. Worn surface of PEEK reinforced with 1% MWCNT at high temperature

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3.3. SEM Analysis. To recognize wear parameters and the effect of wt %MWCNT on the wear loss, the worn out pin faces are examined through SEM and the micro structures are presented in Figure 4. From micro graph it is emphasize that, the worn surface of the MWCNT reinforced PEEK composite is spotless. The micro-cracks and plow up tracks are also present. The structure of the worn surfaces slowly changes from fine scrapes to distinct trenches at higher temperatures [13]. Table 3. ANOVA for Wear loss

Source

Sum of Squares

df

Mean Square

F Value

p-value Prob > F

Model

3.01E-11

10

3.01E-12

9.24

0.0002

A-Speed

6.62E-14

1

6.62E-14

0.20

0.6596

B-Load

1.01E-13

1

1.01E-13

0.31

0.5878

C-Temperature

9.59E-12

1

9.59E-12

29.45

0.0001

D-% MWCNT

1.27E-11

1

1.27E-11

39.03

< 0.0001

AB

1.31E-13

1

1.31E-13

0.40

0.5364

AC

4.64E-13

1

4.64E-13

1.43

0.2538

AD

5.99E-13

1

5.99E-13

1.84

0.1980

BC

2.63E-13

1

2.63E-13

0.81

0.3850

BD

4.38E-13

1

4.38E-13

1.34

0.2671

CD

8.89E-17

1

8.89E-17

0.00

0.9871

Residual

4.23E-12

13

3.26E-13

Lack of Fit

4.23E-12

8

5.29E-13

Pure Error

0

5

0

Cor Total

3.43E-11

23

significant

In significant

4. Conclusion The dry sliding wear test is conducted on Pin on disc for assessing the wear loss in MWCNT reinforced PEEK matrix composites. The following important conclusions drawn from the present study are Mathematical model were developed to analyze the wear loss in the dry sliding wear of MWCNT reinforced PEEK matrix composites. The competence of the models is tested by using ANOVA. The developed models are found to be adequate at 95% confidence level. It is witnessed that the temperature and wt % of MWCNT has a better effect on wear loss in in the dry sliding wear of PEEK matrix composites The worn out surface of MWCNT reinforced PEEK is impeccable. The present investigation shows, PEEK reinforced with 1% MWCNT is an alternative material for steel and other metals due to light weight and high wear resistance at low different temperature. References [1] W.H. Bonner, Patent 3065205, USA, 1962. [2] H. Voss, K. Friedrich, Wear, 116 (1987) 1-18. [3] M.C.Kuo,C.M.Tsai,J .C.Huang, M.Chen, Mat. Chem. and Phy. 9 (2005) 185-195.

D. Kumar and T. Rajmohan / Materials Today: Proceedings 16 (2019) 800–807 [4] J. Bijwe, S. Sukanta, A. Ghosh, Wear 258 (2005) 1536-1542. [5] D.L. Burris, W.G. Sawyer,Wear 261(2006) 410-418. [6] N.L. McCook, M.A. Hamilton, D.L Burris, W.G.Sawyer, Wear (2007) www.elsservier/locate/wear. [7] Y.H.Lai, M.C.Kuo, J.C.Huang, M.Chen, E. mat. 351 (2007) 15-20. [8] G. You, Y.J. Guo xin, R. Yang, J. App. Poly. 117 (2010) 186-193. [9] G.Y.Xie, G.S.Zhuang, G.X.Sui, R.Yang, J. App. Poly. Sci. 119 (2010) 1711-1720. [10] G.Y.Xie, G.X.Sui, R.Yang, Tribol. Let. 38 (2010) 87-96. [11] M.C. Kuo, J.S. Kuo, M.H. Yang, J.C. Huang www.elsevier.com/locate/mat. Chem. Phys. (2010). [12] J.R.Vail , B.A. Krick, K.R. Marchman, W.G. Sawyer, Wear (2010) doi: 10.1016/j.wear.2010.12.003. [13] Rajmohan, J. Thermoplast. Comp. Mat. 1–27 DOI: 10.1177/0892705713518790. [14] J. P. Davim, R. Cardoso, 57, 5 (2005) 181–186. [15] T.Rajmohan, D. Kumar, S. Manimaran, App. Mech. Mat.813-814 (2015) 218-225. [16] T Rajmohan, R Rangarajan, D Seshadhri, L Seshan, D Kumar Applied Mechanics and Materials 813, 235-239

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