the wear characteristics of thermoset polymers composites

Journal of Mechanical Engineering Research and Developments ISSN: 1024-1752 CODEN: JERDFO Vol. 44, No. 3, pp. 322-333 Published Year 2021

322

The wear characteristics of thermoset polymers composites filled

with ceramic particles Mohammed J. Kadhim, Hamza M. Kamal and Layla Muhsan Hasan*

Department of Materials Engineering, College of Engineering, Mustansiriyah University, Baghdad, Iraq.

* Corresponding Author Email: [email protected], [email protected]

ABSTRACT

This article focuses primarily on the evaluation of the hardness and tribological performance of epoxy resin integrated ceramic particles. In particular, epoxy was filled with tungsten carbide (WC) and silicon nitride (SN), using various weight fractions (0, 10, 20 and 30%). The hand-lay route was employed to prepare the composite samples after a surface treatment of the filler particles. The homogeneity of the samples were evaluated by scanning electron microscopy (SEM). The influence of ceramic fillers on tribological performance was presented as wear loss and friction coefficient which were measured at different normal loads of (25, 50, 100) N with two sliding velocities (5, and 7.5) m/s while the sliding distance remained constant. In addition, the influence of the subjected load on the tribological performance was also investigated. The results indicate that filling epoxy with tungsten carbide (WC) and silicon nitride (SN) enhanced the hardness and tribological performance of the epoxy resin. However, tungsten carbide performed better than silicon nitride. Moreover, raising the subjected load increases coefficients of friction for both (5, and 7.5) m/s sliding velocities.

KEYWORDS

Tribological performance, Epoxy resin, Tungsten carbide, Silicon nitride, Ceramics fillers

INTRODUCTION

The main challenge for the most materials engineers is the development of durable composite material. In recent decades, ceramic particles filled polymer composites have drawn the scientists’ interest and attracting scientific research which revealed the significant potential of the polymer composite materials as a type of engineering materials with enhanced wear and friction properties [1,2]. Due to their good tribological, thermal, and mechanical characteristics, polymer composites have become the key part of industrial applications. In addition to their low cost and simple process ability. Polymer composites are excellent candidate for a special type of engineering materials with unique properties [3]. One of the most commonly thermosetting resin used in composite materials as a matrix is epoxy [4]. The dominancy of epoxy resin as a matrix in the composite industry is a result of its unique properties such as good strength, low cost, ability to be used as up to 175 o C, compatibility to most of the common reinforcements [5].

The incorporation of ceramic particles such as tungsten carbide, silicon nitride, silica, alumina as a fillers can enhance the tribological behavior and mechanical characteristics of epoxy resin. Research has been done to evaluate the influence of integrating ceramic particles on the tribological performance and mechanical properties of epoxy resin [6]. Chanshetti et al. evaluated the effect of titanium oxide and tungsten carbide as reinforcing fillers in epoxy matrix on the hardness and wear resistance of the composite. Their observations disclosed that the fillers had a positive influence because they reduced the wear rate as compared to epoxy resin [7]. Kadhim et al. examined the wear and friction characteristic of epoxy reinforced by silicon carbide and boron nitride. Similarly, their results observed that the ceramic carbides enhanced the wear characteristics of epoxy. Particularly, boron carbide samples had the best performance [8]. Correspondingly, Mohan et al reported that the addition of tungsten carbide to glass epoxy reduced the erosion rate as compared to glass epoxy [9].

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The wear characteristics of thermoset polymers composites filled with ceramic particles

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Alumina has been reported as one of the wear resistance enhancer when integrated to epoxy matrix. Bazrgari et al. found that 1% of alumina resulted in significant reduction in wear rate and friction coefficient of epoxy resin [10]. It has been observed in the previous studies that the shape of ceramic particles fillers effects the mechanical properties of epoxy-ceramic composite significantly. Furthermore, the lack of strong adhesion between ceramic particles fillers and polymers has been reported [11]. In the present study, the surface of the ceramic fillers was modified by silane as coupling agent. Silane treatment provides surface modification which lowers the risk of stress concentration and micro cracks initiation. Moreover, it enhances the bonding between the ceramic particles and epoxy which improves the mechanical properties of the composite [11]. The focus of the work is to improve the wear, friction, hardness characteristics of epoxy by incorporating tungsten carbide and silicon nitride as ceramic particles fillers. This study provides a better understanding with experimental basis for the mechanical properties modification of epoxy as a result of the addition of ceramic particles because of their special mechanical properties.

MATERIALS AND METHODS

Two types of ceramic particles were used as filler materials, tungsten carbide (WC) and Silicon nitride (SN) powders, which were provided by DINES PLASTICS, LTD, England. Their properties are illustrated in Table 1

Table 1. Properties of tungsten carbide (WC) and Silicon nitride (SN).

Specification Tungsten carbide Silicon nitride Color Gray-Black Gray

Particle size (0.05-10) μm (0.05-10) μm

Density (g.cm-3) 15.63 3.2

Melting Point (˚C) 2870 1900

Young Modulus (GPa) 650 310

Hardness (Vickers) 2600 1600

Crystal Structure Hexagonal Hexagonal

Ultimate Tensile Strength (MPa) 344 400

For the matrix phase, epoxy resin type (LY556+HY951) system was used that was provided by "Advanced Materials India Pvt. Ltd." The LY 556 epoxy resin is a clear pale-yellow liquid. Its viscosity and density at 25° C are 10000-12000 mPa s and 1.15-1.20 g/cc respectively. While the Hardener HY 917 is a clear liquid with a viscosity of 10-20 mPa s and density of 0.98 g/cc both measured at 25° C. The mixing ratio (parts by weight) is 100 of LY556 and of 10 HY951. Silane was used for the surface modification of the ceramic fillers. It is used as coupling agent which helps in the enhancement of the bonding and adhesion characteristics at the interface of epoxy-ceramic particles.

The procedure of the preparation of epoxy-ceramic particles composite consisted of the following steps: The surface modification of ceramic particles: the ceramic particles fillers were treated with (1%) dilute fresh silane solution and stirred for 5 minutes accompanied by 8 hours drying cycle at 105 0C to enhance the bonding and adhesion characteristics at the interface of epoxy-ceramic particles. Two groups of epoxy resin matrix filled with ceramic particles fillers samples were prepared using hand lay-up route. The mixing ratio of 10:1 of the epoxy resin and its hardener respectively were used. The first group of samples consisted of epoxy as a matrix with 0, 10, 20, and 30% weight fraction of tungsten carbide (WC). The second group of samples consisted of epoxy matrix with 0, 10, 20, and 30% weight fraction of and silicon nitride (SN).


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The treated ceramic particles were incorporated into the epoxy resin with its hardener and mixed manually until uniform distribution of ceramic particles in the matrix were obtained and gel-like paste was achieved. To overcome the problem of precipitation of the ceramic particles in the base of matrix, the particles should be added before the gelation forming .The mixture poured in a mold for 24 hr in order to cure the composite Cylindrical molds made from acrylic plastic were used with dimensions of 10 mm diameter, 20 mm thickness for the wear test and 40 mm diameter, 10 mm thickness for the hardness test. Before the pouring process, the mold were cleaned and lubricated by Vaseline to facilitate the ejection of the samples.

Characterization

In order to investigate the required properties, three samples are prepared for each test into the required geometry according to (ASTM) standard and applying the route for each required test.

Hardness test

Shore hardness (D) device (provided from the "W-Tester Amsler Durometer (DIN 53505-ISO P858))" [12] was used to determine the hardness values of the pure epoxy resin, epoxy with WC, and epoxy with SN

Wear Test

To assess the wear behavior of epoxy- ceramic composite, Pin-on-disk apparatus was used. The test was done according to (ASTM G99)" [13]. The disk used in this test is made from steel with 8 mm thickness and 165 mm diameter. The hardness of the disk is 61 HRC while the surface roughness is 1.3 mm. The wear testing was done using the following steps: A soft cloth soaked in acetone was used to clean the disc and the specimen before the test was performed. The wear test was conducted using different loads (25 N, 50 N, and 100) N with (5, and 7.5) m/s as sliding velocities. The resulted wear values were expressed as weight loss which equals to the difference between the initial and the final weights which were measured using an electronic digital scale with an accuracy of 0.0001 g. (type METTLERTOLEDO manufactured by Switzerland Company. In addition to the weight loss measurements, the coefficient of friction was used as another parameter assess the wear behavior of epoxy-ceramic composite. The coefficient of friction is measured using equation 1[14];

Coefficient of friction =𝐹𝐹𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓

Nominal load (1)

This parameter was calculated with the same conditions that used in weight loss measurement from the applied load and sliding distance.

SEM examination

To ensure the homogeneity of the epoxy- ceramic composite, selected samples from each specimen were examined using "TESCAN Vega II XMU SEM characterization". The selected specimens were coated with 40 nm - 60 nm of gold.

RESULTS AND DISCUSSION

The hardness values for epoxy, epoxy with WC, and epoxy with SN are shown in Figure 1. The harness values increased after the addition of WC and SN to epoxy. Higher values of hardness were obtained as the concentration of the ceramic particles increased for both WC samples and SN samples. This results agreed with Axen and Jacobson [15], Durand et al. [16], and Darak and Sidhu [17] . However, the samples that reinforced by WC observed higher hardness values as compared with the samples that filled with SN using the same weight fraction which is a result of the high hardness of the tungsten carbide particles. The highest hardness values was 116 which obtained by the addition of 30 % weight fraction of WC. Our results agree with the results of Chanshetti et al. that revealed the enhancement of hardness after the addition of WC to epoxy [7].


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Figure 1. Effect of ceramic particles with different weight fraction on the hardness values of epoxy resin.

Surface treatment of WC and SN helps to change the morphology of the ceramic particles and enhanced the bonding between the epoxy and the fillers particles. Which helps in the enhancement of the hardness of the composite material. Figure 2, and 3 exhibit SEM images of epoxy with 30% WC, and Epoxy with 30% of SN. It can be noticed that the WC and SN particles were well dispersed in the epoxy matrix which helps to improve the hardness values strengthening the epoxy matrix by constrain the crack propagation [2].

Figure 2. SEM image of epoxy resin filled with (30%) WC particles.

Figure 3. SEM image of epoxy resin filled with (30%) Si3N4 particles.

Figure 4-9 display the wear loss versus weight fraction of the fillers at different loads and sliding velocities. The wear loss of epoxy- ceramic composite increased as the load and sliding velocities increased for both of the fillers.

0306090120150

0 10 20 30WC 66 82 97 116SN 66 70 84 101

Shore

Hard

ness D

Wt % of Ceramic Particles

Hardness versus Weight fraction of Ceramics Particles

WC SN


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Although, samples filled with SN obtained higher wear loss than the samples reinforced by WC. The highest wear loss was 18.9 x 10 -3 g at 100 N, and 7.5 m/s. In addition, the wear loss was significantly decreased after the addition of WC and SN. The lowest wear loss was 3x10 -3 g which was observed for the sample contained 30% of WC 25 N and 5 m/s .While 11.7x10 -3 g wear loss for the epoxy resin at the same load and sliding velocity.

This enhancement in the wear characteristics of the epoxy after the incorporation of the ceramic fillers especially (WC) is due to the unusual wear characteristics and hardness values of these fillers. Besides, the effect of the surface treatment that improved the wear characteristics as a result of the fillers surface modification and the better interfacial bonding which leads to the enhancement of stress transformation from epoxy to ceramic particles. Moreover, this treatment improve the hydrophobicity to inhibit moisture infiltration and cause more efficient distribution of the fillers in the resin.

Figure 4. Epoxy composite wear loss versus weight fraction of ceramic particles at load of 25 N, 5 m/s sliding velocity.

Figure 5. Epoxy composite wear loss versus weight fraction of ceramic particles at load of 50 N, and 5m/s sliding velocity.

0102030

0 10 20 30WC 11.7 9.1 6.7 3.2SN 11.7 10.2 8.1 5.6

Wear

Loss

x !0-3

(g)


Wear Loss versus Weight fraction of Ceramics Particles at 25 N and 5 m/s.

WC SN

0102030

0 10 20 30WC 17.9 13.1 9.9 6.4SN 17.9 15.6 11.2 8.9

Wear

Loss

x !0-3

(g)



WC SN


327

Figure 6. Epoxy composite wear loss versus weight fraction of ceramic carbides at load of 100 N, and 5 m/s sliding velocity.

Figure 7. Epoxy composite wear loss versus weight fraction of ceramic carbides at load of 25 N, and 7.5 m/s sliding velocity.

0102030

0 10 20 30WC 24.7 17.1 13.6 9.1SN 24.7 19.8 16.9 13.7

Wear

Loss

x !0-3

(g)



WC SN

0102030

0 10 20 30WC 13.4 10.9 7.6 4.7SN 13.4 12.1 9.4 7.1

Wear

Loss

x !0-3

(g)


Wear Loss versus Weight fraction of Ceramics Particles at 25 N and 7.5 m/s.

WC SN


328

Figure 8. Wear loss of epoxy resin versus weight fraction of ceramic carbides at load of 50 N, 7.5 m/s sliding velocity.

Figure 9. Wear loss of epoxy resin versus weight fraction of ceramic carbides at load of 100 N, 7.5 m/s sliding velocity.

The coefficients of friction are presented in Figures 10-15. The applied loads were 25N, 50N and 100N. The sliding velocities were 5m/s and 7.5m/s while sliding distance remained the same. The friction coefficients reduced as the weight percentages of the ceramic fillers increased at all the applied loads and with all the sliding velocities. The coefficient of friction was 0.6 for epoxy without fillers and lowered to 0.47, and 0.35 after the addition of 30 %wt. of WC and SN respectively at 25 N load and 5 m/s. The samples filled with tungsten carbide had lower coefficient of frictions than the samples that contained silicon nitride with the same weight percentages. For instance, at 30% wt. of WC the coefficient of friction was 0.58 while it was 0.63 for the same wt. of SN, Figure 12.

Accordingly, due to the heat resistance characteristics of ceramic fillers, they play a critical role in decreasing the interfacial temperature resulting in a remarkable improvement in the coefficient of friction values of the

0102030

0 10 20 30WC 20.4 16.7 12.9 8.6SN 20.4 19.4 16.9 12.5

Wear

Loss

x 10-3

(g)



WC SN

0102030

0 10 20 30WC 26.9 22.1 19.4 14.8SN 26.9 24.9 21.1 18.9

Wear

Loss

x !0-3

(g)



WC SN


329

epoxy resin. On the other hand, the friction coefficients increases as the subjected load raised for both 5, 7.5 m/s sliding velocities. For instance the coefficients of friction were 0.47, 0.53 and 0.58 for the samples contained 30% WC at loads of 25, 50 and 100 respectively with 5 m/s sliding velocity. This behavior may be a result of the increment of the contact pressure which raises the interfacial temperature which leads to higher values of the friction force.

Figure 10. Friction coefficient versus weight fraction of ceramic particles at load of 25N and 5m/s sliding velocity.

Figure 11. Friction coefficient versus weight fraction of ceramic particles at load of 50N, and 5m/s sliding velocity.

00.5

1

0 10 20 30WC 0.6 0.56 0.53 0.47SN 0.6 0.59 0.57 0.53

Coeff

icient

of Fr

iction


Coefficient of Friction versus Weight fraction of Ceramics Particles at 25 N and 5 m/s.

WC SN

00.5

1

0 10 20 30WC 0.65 0.61 0.58 0.53SN 0.65 0.63 0.61 0.57

Coeff

icient

of Fr

iction



WC SN


330

Figure 12. Friction coefficient versus weight fraction of ceramic particles at load of 100N, and 5m/s sliding velocity.

Figure 13. Friction coefficient versus weight fraction of ceramic particles at load of 25N, and 7.5m/s sliding velocity.

00.5

1

0 10 20 30WC 0.72 0.68 0.63 0.58SN 0.72 0.7 0.67 0.63

Coeff

icient

of Fr

iction



WC SN

00.5

1

0 10 20 30WC 0.63 0.59 0.56 0.51SN 0.63 0.61 0.59 0.55

Coeff

icient

of Fr

iction


Coefficient of Friction versus Weight fraction of Ceramics Particles at 25 N and 7.5 m/s.

WC SN


331



CONCLUSIONS

Tungsten carbide and silicon nitride were used as fillers in epoxy matrix to raise the hardness and improve wear and friction characteristics of epoxy. Different weight fraction of the ceramic particles were used. The surface of the ceramic particles were treated by silane to improve the bonding between the epoxy and the filler. Experiments was done to evaluate the effect of tungsten carbide and silicon nitride as reinforcing fillers in epoxy matrix on the hardness and wear resistance of the composite On this basis, we conclude that:

1. The hardness were increased as the weight percentage of the fillers increase. Nonetheless, tungsten carbide reinforced samples reported higher hardness values compared to silicon nitride filled samples using the same weight proportion. Moreover, the highest hardness values were achieved by adding 30% tungsten carbide weight fraction.

00.5

1

0 10 20 30WC 0.68 0.65 0.6 0.56SN 0.68 0.67 0.63 0.59

Coeff

icient

of Fr

iction



WC SN

00.5

1

0 10 20 30WC 0.76 0.71 0.67 0.61SN 0.76 0.73 0.7 0.66

Coeff

icient

of Fr

iction



WC SN


332

2. In the epoxy matrix, the WC and SN particles were well distributed, which helps to increase the hardness values that strengthen the epoxy matrix by limiting the propagation of cracks as can be shown in the SEM images

3. Epoxy-ceramic composite wear loss increased as the load and sliding velocities for both fillers. Samples loaded with silicon nitride, however, achieved greater wear loss than the samples reinforced by silicon nitride.

4. Better tribological behavior were obtained after the addition of tungsten carbide and silicon nitride. This was presented by wear loss and friction coefficient reduction. In addition, the lowest wear loss was was observed for the sample contained 30% of WC 25 N and 5 m/s.

5. Increasing applied load raises the coefficient of friction. On the other hand, as the weight percentages of the ceramic fillers increased at all the applied loads and with all the sliding velocities, the friction coefficients decreased.

ACKNOWLEDGMENT

The authors highly appreciate the support for this work from Mustansiriyah University, College of Engineering.

REFERENCES

[1] G. Shi, M.Q. Zhang, and M.Z. Rong, “Friction and wear of low nanometer Si3N4 filled epoxy composites”, Wear, Vol. 254, No. 7-8, Pp. 784-796, 2003.

[2] N. Ramdani, J. Wang, and H. Wang, “Mechanical and thermal properties of silicon nitride reinforced polybenzoxazine nanocomposites”, Composites science and technology, Vol. 105, Pp. 73-79, 2014.

[3] N. Ai, S. Hussein, and M. Jawad, “Effect of Al2O3 and SiO2 Nanopartical on Wear, Hardness and Impact Behavior of Epoxy Composites”, Chemistry and Materials Research, Vol. 7, No. 4, Pp. 34-40, 2015.

[4] M.K. Reddy, V.S. Babu, and K.S. Srinadh, “Mechanical properties of tungsten carbide nanoparticles filled epoxy polymer nano composites”, Materials Today: Proceedings, Vol. 26, Pp. 2711-2713, 2020.

[5] S.A. Bello, J.O. Agunsoye, and S.B. Hassan, “Epoxy Resin Based Composites, Mechanical and Tribological Properties: A Review”, Tribology in Industry, Vol. 37, No. 4, Pp. 500-524, 2015.

[6] S.R. Ranganatha, H.C. Chittappa, and D. Tulsidas, “Investigation on Three-Body Abrasive Wear of Al2O3 Filler on CFRP Composites”, International Journal of Advanced Engineering Research and Studies, Vol. 2, No. 3, Pp. 83-85, 2013.

[7] N.G. Chanshetti, and A.S. Pol, “Wear behavior of TiO2 and WC reinforced epoxy resin composites”, Int. Res. J. Eng. Technol, Vol. 3, Pp. 2395-0056, 2016.

[8] M.J. Kadhim, H.M. Kamal, and A.H. Majeed, “The Tribological Behavior of Epoxy Matrix Composite Reinforced by Ceramic Carbides”, Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, Vol. 70, No. 2, Pp. 76-88, 2020.

[9] M. Mohan, C.R. Mahesha, and B.M. Rajaprakash, “Erosive wear behaviour of WC filled glass epoxy composites”, Procedia Engineering, Vol. 68, Pp. 694-702, 2013.

[10] D. Bazrgari, F. Moztarzadeh, and S. Alvani, “Mechanical properties and tribological performance of epoxy/Al2O3 nanocomposite”, Ceramics International, Vol. 44, No. 1, Pp. 1220-1224, 2018.


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[11] J. Abenojar, J.C. Del Real, and M.A. Martinez, “Effect of silane treatment on SiC particles used as reinforcement in epoxy resins”, The Journal of Adhesion, Vol. 85, No. 6, Pp. 287-301, 2009.

[12] ASTM D2240-05. Standard test method for rubber property durometer hardness, 2015.

[13] ASTM G99-05. Standard test method for wear testing with a pin-on-disk apparatus, 2015.

[14] R.J. Bayer, Mechanical Wear Fundamentals and Testing, revised and expanded. CRC Press, 2004.

[15] N. Axen, and S. Jacobson, “A model for the abrasive wear resistance of multiphase materials”, Wear, Vol. 174, No. 1-2, Pp. 187-199, 1994.

[16] J.M. Durand, M. Vardavoulias, and M. Jeandin, “Role of reinforcing ceramic particles in the wear behavior of polymer-based model composites”, Wear, Vol. 181, Pp. 833-839, 1995.

[17] A.R. Darak, and J. S. Sidhu, “Study of mechanical properties of epoxy-based composites”, International Research Journal of Modernization in Engineering Technology and Science, Vol. 3, No. 1, Pp. 238-248, 2021.

the wear characteristics of thermoset polymers composites

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