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Tribo-Mechanical Responses of Glass Fiber Reinforced Polymer Hybrid Nanocomposites
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 18 (2019) 4042–4047
www.materialstoday.com/proceedings
ICMPC-2019
Tribo-Mechanical Responses of Glass Fiber Reinforced Polymer Hybrid Nanocomposites Smaranika Nayaka, R.K.Nayakb*, I.Panigrahia, A.K.Sahooa a
School of Mechanical Engineering, KIIT Deemed to be University, Bhubaneswar-751024 b Department of Materials and Metallugical Engineering ,MANIT,Bhopal -462003,india
Abstract In the trending materials technology, nano composites are gaining importance due to enhanced mechanical, thermal and optical properties. Among various nanofillers used in fiber reinforced polymer nanocomposites, nanoclays have received several attractions among academia and researchers due to its high aspect ratio and characteristic exfoliation/intercalation properties. The stiffness of glass fibre reinforced polymer composites is not very high in comparison to carbon fibres. In the present work, an attempt has been made to enhance the stiffness and tribological properties of glass fibres by mixing nanoclays in the epoxy matrix. Hand lay up method was adopted to make ten layered glass fibre reinforced polymer hybrid composite. The weight percentage of nanoclay was 1%, 3%, 5%, and 7% to understand the behaviour of the hybrid composites. It was observed that 5% loading of nanoclay shows the optimum amount at which all the properties like hardness, impact strength, flexural strength and specific wear rate was increased. However, with further increase in nanoclays, all the above said properties were deteriorated. At 5% nanoclay content, hardness increased by 33.8%, impact strength by 74.8%, flexural strength and modulus by 37.5% and 37.67% respectively. Hence the above hybrid composite may be considered as a better composite for various structural and industrial applications. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: GFRP; nanoclay; flexural strength; impact energy;Dry abrasion wear ; SWR
1. Introduction Composites play a vital role in this present era. It not only makes progressive contribution to its widest application but its own characteristic properties like high strength, high stiffness, high fracture toughness, low density, corrosion resistance, wear resistance etc. make it all together a very versatile and different material. We can
* Corresponding author. Tel.: +91-8763724080; E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
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find an enormous potential of these composite materials starting from sports goods to aircraft components. It comprises of complex materials showing distinctive anisotropic properties. Basically it consists of three essential parts fiber, matrix and the coupling agents. Glass fiber reinforced polymer composites (GFRP) are widely used in windmill blade, military application, aerospace, automotive etc. due to its advantageous properties like high strength, non-corrosive and light weight [1-3]. However its stiffness is found to be less in comparison to conventional materials like aluminum, steel etc. Hence, nanoclays are added to the epoxy matrix to increase the stiffness of the composites for structural applications. Nano-composites are a specific category of materials which involves addition of nano sized particles ((10⁻⁹) scale) into polymer or matrix which results in a considerable enhancement in different mechanical [4,5] and optical properties. Nano-fillers are basically classified as metals (Al, Fe, etc.), metal oxide (Al₂Oз, TiO₂, ZnO, etc.), organic (CNT, SWCNT, MWCNT, graphene, etc.), inorganic (SiC, SiO₂, etc.) and others (MoS₂ nanoclay, WS₂, etc.)[6]. It has been observed that the mechanical properties and thermal stability get enhanced when nano fillers are added into the polymer matrix while permeability gets lowered in comparison to neat epoxy glass fibre reinforced polymer composites[7,8]. Due to superior properties like thermal, mechanical, low density and cheap manufacturing costs, nano Al₂Oз and TiO₂ are found to be the best among various nano fillers used [9-11]. For different hydrothermal applications , the durability of nano Al₂Oз based glass fiber reinforced composite was also studied by Nayak et al. [12]. Nanoclay have gained numerous attention from several researchers and academia due to its characteristic intercalation/exfoliation properties and high aspect ratio[13]. When the nanoclays are well dispersed in the epoxy matrix, the mechanical properties of fiber reinforced polymers are strengthened[14]. The influence of addition of montmorillonite nanoclay on CFRPs was investigated by Zainuddin et al.[15] and reported that flexural modulus, flexural strength and glass transition temperature were enhanced by about 8.7%, 17.4% and 16ᵒC with incorporation of 2 wt%. Avila et al.[16] investigated the low-velocity impact response of a nanoclay modified glass fibre reinforced composite where the laminate with 10% content of nanoclay did not perform as well as the 5% content condition. Reinforcement with nanoclay is found to be effective at high temperature. Good material properties can be achieved using 2 wt% nanoclay after exposing to UV as investigated by Tcherbi-Narteh et al.[17]. Sivasaravanan S et al.[18] investigated that the impact results showed an increasing trend with the addition of nano-clay into the epoxy matrix. Ermias G Koricho et al. [19] studied the low velocity impact behaviour of pristine and micro/nano filled GFRP compostes for vehicular applications that is bumper system. It has been observed that the addition of nanoclay to the epoxy matix of GFRP composite results in increase in flexural properties[20], interlaminar shear strength[21] and decrease in thermal expansion co-efficient[22]. However, if the amount of nanoclay goes beyond an optimum level, the resultant mechanical properties gets reduced [23]. In the present study, Cloisite 30B MMT nanoclay has been employed (viz 0%, 1%, 3%, 5% and 7%) to modify the existing epoxy matrix system. By hand layup method five different hybrid nanocomposites of varying percentages of nanoclay were fabricated. These hybrid nanocomposites were investigated as per ASTM standard to determine its characteristic properties like hardness, impact, flexural and dry abrasive wear behavior. 2. Experimental Work 2.1 Materials In the present study, Cloisite 30B MMT nanoclay is used which is supplied by Southern Clay Products Inc (Gonzales, TX, USA). The fabrication of composites was carried out using plain woven E-Glass of 360gsm and density 2.52 g/cm3 from Owens Corning, India. Epoxy (Diglycidyl ether of Bisphenol A) marketed as Lapox L-12 of density 1.16 g/cm3 and Triethylene tetra amine (hardener) labeled as K-6 procured from Atul Industries, India were used. The nanoclay in varying weight percentages (viz 0%, 1%, 3%, 5%, and 7%) was added to the epoxy matrix system. 2.2 Fabrication Method The required percentage of nanoclays was dried in a oven at 900C for 5hrs in order to remove the moisture. Then it was mixed with epoxy in a glass beaker. After that, it was mechanically stirred at 600rpm. It was stirred magnetically at 300 rpm followed by sonication of Athena technology (ATP-150,20KHz). During the entire
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process of mixing constant temperature was maintained. After that, hardener was mixed in the ratio of 1:10 in the epoxy matrix until the system was cooled down to the room temperature. The hand lay up method was used to fabricate the composites by reinforcing ten layers of glass fibres in nano clay modified polymer matrix. The roller was applied to remove the entrapped air bubbles and voids from the composites. Then the nano modified glass fibre reinforced composites were kept under 10 kg loads for 24 hours at room temperature for initial curing. After that, specimens were cut to required dimensions as per the specifications and finally cured in an oven at 140 0C for six hours before testing. 3. Results and Discussions 3.1 Hardness The hardness of different nanocomposites was determined as per ASTM D2583 standard using Barcol Hardness Tester supplied by Barber Colman, USA. This hardness feature is essential to know the wear behaviour of the material. Five specimens of each composite having 0%, 1%, 3%, 5% and 7% nanoclays were tested and their average values were reported. Fig.1. shows the hardness of neat epoxy based GFRP and GFRP with varying percentages of nanoclay. It was observed that with increase in percentage of nanoclay upto 5% hardness increases; however, it decreases with further increase in nanoclay content. The hardness of the nanocomposite having 5% nano clay was increased by 33.8% as compared to others.
Fig.1. Hardness of different composites
3.2 Impact Strength The ability to resist the fracture under impact/shock loads is nothing but impact resistance of the composites. Here the impact strength was evaluated using Izod impact testing machine where the specimen is held in vertical position with a pendulum striking at the tip position. The required specimens are rectangular in shape having dimension 64 mm × 12.7 mm × 2.54 mm. The samples were cut as per the ASTM D256 standard. Five specimens of each type were tested. Fig.2 shows that the impact energy increases with increase in nanoclay content and is maximum at 5% nanoclay. Fig.3 shows the different specimens before and after impact testing. It can also be concluded that almost a brittle kind of fracture occurred at 0% and 7%, while maximum deformation of fibres was seen at 5% due to more amount of impact energy absorption. The nanocomposite having 5% loading of nanoclay improves the impact strength by 74.8% as compared to plain glass fiber reinforced polymer composite.
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Fig.2. Impact Energy of different Specimens
Fig.3. Specimens with varying wt.% of nanoclay before and after impact tests.
3.3 Flexural Strength According to ASTM D7264 standard, flexural strength and modulus were determined using Instron 3382 Universal Testing Machine .Rectangular specimens of dimensions 100mm x12.7mm x3 mm were cut for the test. The span length was kept at 60 mm and cross head speed was maintained at 2mm/min throughout the test. Five specimens of each type were tested and their average values were considered. From the fig.4(a-b), it is observed that the flexural strength is the highest at 5% loading of nanoclay as compared to other nanocomposites. But beyond that there is a decline in flexural strength . Similarly, the modulus of the 5% nanoclay is also found to be the greatest among other percentage loading of nanoclay which is mainly attributed to the finer dispersion of nanoclay in the epoxy matrix. Composites with nanoclay loading uptil 5% shows good increasing trends of flexural strength and modulus and decreases further with increase in nanoclay.The compsoites having 5% nanoclay improve the flexural strength and modulus by 37.5% and 37.67% respectively as compared to neat/plain glass fiber reinforced polymer composites.
Fig.4. (a) Flexural Strength; (b) Flexural Modulus of nanocomposite
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3.4 Dry Abrasive Wear Dry abrasive wear test was conducted using dry abrasion tester of DUCOM TR-50. Specimens of required dimensions (76mm x 25.5mm x 3 mm) were cut according to the ASTM G65 standard. Abrasive particle of dry sand of grade AFS 60 was flown between the wheel and the desired specimen. A constant load of 25.5 N was applied with the help of lever arm and rotating wheel speed was maintained at 125 rpm. With respect to density and weight loss, the volume loss was calculated. Specific wear rate (SWR) was then calculated from the following equation SWR = ∆V/L x D (1) where ∆V is the loss in volume in mmᶟ, L is the applied load applied (N) and D is the sliding distance in (m). Fig.5 shows that the specific wear rate versus types of composite having different weight percentage of nanoclay. It is observed that at 5% loading of nanoclay has the lowest SWR as compared to other hybrid nanocomposites. As the hardness number of the specimen is more, so it is obvious that the wearing of the above mentioned specimen will be the least. Hence, the nanoclay loading of 5% gives us better results and Fig.6 (a-e) shows the different specimens subjected to dry abrasive wear test. It is observed that maximum volume loss was for 0% and 7% nanoclay content. The SWR of the nanocomposite having 5% nanoclay was reduced by 20% as compared to other composites.
Fig.5. Specific wear rate of different nanocomposites
Fig. 6. Dry Abrasive wear test of different composites corresponding to (a)0%, (b)1%, (c)3%, (d)5% and (e)7% loadings of nanoclay.
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4. Conclusion Nanoclay reinforced epoxy polymer matrix nanocomposite were fabricated and the mechanical and tribological properties were investigated. The following conclusion may be drawn. The hardness of the composites with varying percentages of nanoclay (0%, 1%, 3%, 5%, and 7% of wt.) was increased up to 5% loading of nanoclay and decreases further increase in it. The toughness of the composites which is a measure of impact energy was increased with the nanoclay content. The maximum impact energy was found to be at 5% loading of nanoclay which was found to be 40.8% more than neat epoxy glass fibre reinforced composite. The flexural strength and modulus of the nanocomposite having 5% nanoclay was increased by 37.5% and 37.67% respectively in comparison to neat epoxy based glass fibre reinforced composite. The SWR of the nanocomposite having 5% nanoclay was found to be less which indicates good wear behaviour of the material. References 1. Shetty, M. R., Vijay Kumar, K. R., Sudhir, S., Raghu, P., Madhuranath, A. D., & Rao, R. M. V. G. K. Journal of reinforced plastics and composites, 19(8)(2000), 606-620. 2. Hug, G., Thévenet, P., Fitoussi, J., & Baptiste, D. (2006). Effect of the loading rate on mode I interlaminar fracture toughness of laminated composites. Engineering Fracture Mechanics, 73(16), 2456-2462. 3. Zhou, Y., Pervin, F., Rangari, V. K., & Jeelani, S. (2007). Influence of montmorillonite clay on the thermal and mechanical properties of conventional carbon fiber reinforced composites. Journal of Materials Processing Technology, 191(1-3), 347-351. 4. Ramesh Kumar Nayak, Bankim Chandra Ray, Archives of Civil and Mechanical Engineering, 18.4(2018) 1597–1607. 5. Nayak, Ramesh Kumar, and Bankim Chandra Ray, Polymer-Plastics Technology and Engineering (2018) 1-11. 6. Naffakh, M., Díez-Pascual, A. M., Marco, C., Ellis, G. J., & Gomez-Fatou, M. A, Progress in Polymer Science, 38(8) (2013) 1163-1231. 7. Anjana, R., & George, K. E. (2012). Reinforcing effect of nano kaolin clay on PP/HDPE blends. International journal of engineering research and applications, 2(4), 868-872. 8. Garcia, M., Van Vliet, G., Jain, S., Schrauwen, B., Sarkissov, A., Van Zyl, W. E., & Boukamp, B. (2004). Polypropylene/SiO 2 nanocomposites with improved mechanical properties. Reviews on advanced materials science, 6(2), 169-175. 9. Daneshpayeh, S., Ghasemi, F. A., Ghasemi, I., & Ayaz, M. (2016). Predicting of mechanical properties of PP/LLDPE/TiO2 nano-composites by response surface methodology. Composites Part B: Engineering, 84, 109-120. 10. Nayak, R. K., Dash, A., & Ray, B. C. (2014). Effect of epoxy modifiers (Al2O3/SiO2/TiO2) on mechanical performance of epoxy/glass fiber hybrid composites. Procedia materials science, 6, 1359-1364. 11. Golru, S. S., Attar, M. M., & Ramezanzadeh, B. (2014). Studying the influence of nano-Al2O3 particles on the corrosion performance and hydrolytic degradation resistance of an epoxy/polyamide coating on AA-1050. Progress in Organic Coatings, 77(9), 1391-1399. 12. Nayak, R. K., & Ray, B. C. (2017). Water absorption, residual mechanical and thermal properties of hydrothermally conditioned nano-Al2O3 enhanced glass fiber reinforced polymer composites. Polymer Bulletin, 74(10), 4175-4194. 13. Amir, W. W., Jumahat, A., & Mahmud, J. (2015). Effect of nanoclay content on flexural properties of glass fiber reinforced polymer (GFRP) composite. J. Teknol, 76, 31-35. 14. Timmerman, J. F., Hayes, B. S., & Seferis, J. C. (2002). Nanoclay reinforcement effects on the cryogenic microcracking of carbon fiber/epoxy composites. Composites Science and Technology, 62(9), 1249-1258. 15. Zainuddin, S., Hosur, M. V., Zhou, Y., Narteh, A. T., Kumar, A., & Jeelani, S. (2010). Experimental and numerical investigations on flexural and thermal properties of nanoclay–epoxy nanocomposites. Materials Science and Engineering: A, 527(29-30), 7920-7926. 16. Avila, A. F., Soares, M. I., & Neto, A. S. (2007). A study on nanostructured laminated plates behavior under low-velocity impact loadings. International journal of impact engineering, 34(1), 28-41. 17. Tcherbi-Narteh, A., Hosur, M., Triggs, E., & Jeelani, S. (2013). Thermal stability and degradation of diglycidyl ether of bisphenol A epoxy modified with different nanoclays exposed to UV radiation. Polymer degradation and stability, 98(3), 759-770. 18. Sivasaravanan, S., & Raja, V. B. (2014). Impact characterization of epoxy LY556/E-glass fibre/nano clay hybrid nano composite materials. Procedia Engineering, 97, 968-974. 19. Koricho, E. G., Khomenko, A., Haq, M., Drzal, L. T., Belingardi, G., & Martorana, B. (2015). Effect of hybrid (micro-and nano-) fillers on impact response of GFRP composite. Composite Structures, 134, 789-798. 20. Morfologi, S., & dan Mekanik, T. (2013). Glass fiber and nanoclay reinforced polypropylene composites: Morphological, thermal and mechanical properties. Sains Malaysiana, 42(4), 537-546. 21. Devendra, K., & Rangaswamy, T. (2012). Evaluation of thermal properties of E-Glass/Epoxy Composites filled by different filler materials. International journal of computational engineering research, 2(5), 1708-1714. 22. Dorigato, A., Morandi, S., & Pegoretti, A. (2012). Effect of nanoclay addition on the fiber/matrix adhesion in epoxy/glass composites. Journal of Composite materials, 46(12), 1439-1451. 23. Chan, M. L., Lau, K. T., Wong, T. T., Ho, M. P., & Hui, D. (2011). Mechanism of reinforcement in a nanoclay/polymer composite. Composites Part B: Engineering, 42(6), 1708-1712.
ScienceDirect Materials Today: Proceedings 18 (2019) 4042–4047
www.materialstoday.com/proceedings
ICMPC-2019
Tribo-Mechanical Responses of Glass Fiber Reinforced Polymer Hybrid Nanocomposites Smaranika Nayaka, R.K.Nayakb*, I.Panigrahia, A.K.Sahooa a
School of Mechanical Engineering, KIIT Deemed to be University, Bhubaneswar-751024 b Department of Materials and Metallugical Engineering ,MANIT,Bhopal -462003,india
Abstract In the trending materials technology, nano composites are gaining importance due to enhanced mechanical, thermal and optical properties. Among various nanofillers used in fiber reinforced polymer nanocomposites, nanoclays have received several attractions among academia and researchers due to its high aspect ratio and characteristic exfoliation/intercalation properties. The stiffness of glass fibre reinforced polymer composites is not very high in comparison to carbon fibres. In the present work, an attempt has been made to enhance the stiffness and tribological properties of glass fibres by mixing nanoclays in the epoxy matrix. Hand lay up method was adopted to make ten layered glass fibre reinforced polymer hybrid composite. The weight percentage of nanoclay was 1%, 3%, 5%, and 7% to understand the behaviour of the hybrid composites. It was observed that 5% loading of nanoclay shows the optimum amount at which all the properties like hardness, impact strength, flexural strength and specific wear rate was increased. However, with further increase in nanoclays, all the above said properties were deteriorated. At 5% nanoclay content, hardness increased by 33.8%, impact strength by 74.8%, flexural strength and modulus by 37.5% and 37.67% respectively. Hence the above hybrid composite may be considered as a better composite for various structural and industrial applications. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019 Keywords: GFRP; nanoclay; flexural strength; impact energy;Dry abrasion wear ; SWR
1. Introduction Composites play a vital role in this present era. It not only makes progressive contribution to its widest application but its own characteristic properties like high strength, high stiffness, high fracture toughness, low density, corrosion resistance, wear resistance etc. make it all together a very versatile and different material. We can
* Corresponding author. Tel.: +91-8763724080; E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
S. Nayak et al./ Materials Today: Proceedings 18 (2019) 4042–4047
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find an enormous potential of these composite materials starting from sports goods to aircraft components. It comprises of complex materials showing distinctive anisotropic properties. Basically it consists of three essential parts fiber, matrix and the coupling agents. Glass fiber reinforced polymer composites (GFRP) are widely used in windmill blade, military application, aerospace, automotive etc. due to its advantageous properties like high strength, non-corrosive and light weight [1-3]. However its stiffness is found to be less in comparison to conventional materials like aluminum, steel etc. Hence, nanoclays are added to the epoxy matrix to increase the stiffness of the composites for structural applications. Nano-composites are a specific category of materials which involves addition of nano sized particles ((10⁻⁹) scale) into polymer or matrix which results in a considerable enhancement in different mechanical [4,5] and optical properties. Nano-fillers are basically classified as metals (Al, Fe, etc.), metal oxide (Al₂Oз, TiO₂, ZnO, etc.), organic (CNT, SWCNT, MWCNT, graphene, etc.), inorganic (SiC, SiO₂, etc.) and others (MoS₂ nanoclay, WS₂, etc.)[6]. It has been observed that the mechanical properties and thermal stability get enhanced when nano fillers are added into the polymer matrix while permeability gets lowered in comparison to neat epoxy glass fibre reinforced polymer composites[7,8]. Due to superior properties like thermal, mechanical, low density and cheap manufacturing costs, nano Al₂Oз and TiO₂ are found to be the best among various nano fillers used [9-11]. For different hydrothermal applications , the durability of nano Al₂Oз based glass fiber reinforced composite was also studied by Nayak et al. [12]. Nanoclay have gained numerous attention from several researchers and academia due to its characteristic intercalation/exfoliation properties and high aspect ratio[13]. When the nanoclays are well dispersed in the epoxy matrix, the mechanical properties of fiber reinforced polymers are strengthened[14]. The influence of addition of montmorillonite nanoclay on CFRPs was investigated by Zainuddin et al.[15] and reported that flexural modulus, flexural strength and glass transition temperature were enhanced by about 8.7%, 17.4% and 16ᵒC with incorporation of 2 wt%. Avila et al.[16] investigated the low-velocity impact response of a nanoclay modified glass fibre reinforced composite where the laminate with 10% content of nanoclay did not perform as well as the 5% content condition. Reinforcement with nanoclay is found to be effective at high temperature. Good material properties can be achieved using 2 wt% nanoclay after exposing to UV as investigated by Tcherbi-Narteh et al.[17]. Sivasaravanan S et al.[18] investigated that the impact results showed an increasing trend with the addition of nano-clay into the epoxy matrix. Ermias G Koricho et al. [19] studied the low velocity impact behaviour of pristine and micro/nano filled GFRP compostes for vehicular applications that is bumper system. It has been observed that the addition of nanoclay to the epoxy matix of GFRP composite results in increase in flexural properties[20], interlaminar shear strength[21] and decrease in thermal expansion co-efficient[22]. However, if the amount of nanoclay goes beyond an optimum level, the resultant mechanical properties gets reduced [23]. In the present study, Cloisite 30B MMT nanoclay has been employed (viz 0%, 1%, 3%, 5% and 7%) to modify the existing epoxy matrix system. By hand layup method five different hybrid nanocomposites of varying percentages of nanoclay were fabricated. These hybrid nanocomposites were investigated as per ASTM standard to determine its characteristic properties like hardness, impact, flexural and dry abrasive wear behavior. 2. Experimental Work 2.1 Materials In the present study, Cloisite 30B MMT nanoclay is used which is supplied by Southern Clay Products Inc (Gonzales, TX, USA). The fabrication of composites was carried out using plain woven E-Glass of 360gsm and density 2.52 g/cm3 from Owens Corning, India. Epoxy (Diglycidyl ether of Bisphenol A) marketed as Lapox L-12 of density 1.16 g/cm3 and Triethylene tetra amine (hardener) labeled as K-6 procured from Atul Industries, India were used. The nanoclay in varying weight percentages (viz 0%, 1%, 3%, 5%, and 7%) was added to the epoxy matrix system. 2.2 Fabrication Method The required percentage of nanoclays was dried in a oven at 900C for 5hrs in order to remove the moisture. Then it was mixed with epoxy in a glass beaker. After that, it was mechanically stirred at 600rpm. It was stirred magnetically at 300 rpm followed by sonication of Athena technology (ATP-150,20KHz). During the entire
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process of mixing constant temperature was maintained. After that, hardener was mixed in the ratio of 1:10 in the epoxy matrix until the system was cooled down to the room temperature. The hand lay up method was used to fabricate the composites by reinforcing ten layers of glass fibres in nano clay modified polymer matrix. The roller was applied to remove the entrapped air bubbles and voids from the composites. Then the nano modified glass fibre reinforced composites were kept under 10 kg loads for 24 hours at room temperature for initial curing. After that, specimens were cut to required dimensions as per the specifications and finally cured in an oven at 140 0C for six hours before testing. 3. Results and Discussions 3.1 Hardness The hardness of different nanocomposites was determined as per ASTM D2583 standard using Barcol Hardness Tester supplied by Barber Colman, USA. This hardness feature is essential to know the wear behaviour of the material. Five specimens of each composite having 0%, 1%, 3%, 5% and 7% nanoclays were tested and their average values were reported. Fig.1. shows the hardness of neat epoxy based GFRP and GFRP with varying percentages of nanoclay. It was observed that with increase in percentage of nanoclay upto 5% hardness increases; however, it decreases with further increase in nanoclay content. The hardness of the nanocomposite having 5% nano clay was increased by 33.8% as compared to others.
Fig.1. Hardness of different composites
3.2 Impact Strength The ability to resist the fracture under impact/shock loads is nothing but impact resistance of the composites. Here the impact strength was evaluated using Izod impact testing machine where the specimen is held in vertical position with a pendulum striking at the tip position. The required specimens are rectangular in shape having dimension 64 mm × 12.7 mm × 2.54 mm. The samples were cut as per the ASTM D256 standard. Five specimens of each type were tested. Fig.2 shows that the impact energy increases with increase in nanoclay content and is maximum at 5% nanoclay. Fig.3 shows the different specimens before and after impact testing. It can also be concluded that almost a brittle kind of fracture occurred at 0% and 7%, while maximum deformation of fibres was seen at 5% due to more amount of impact energy absorption. The nanocomposite having 5% loading of nanoclay improves the impact strength by 74.8% as compared to plain glass fiber reinforced polymer composite.
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Fig.2. Impact Energy of different Specimens
Fig.3. Specimens with varying wt.% of nanoclay before and after impact tests.
3.3 Flexural Strength According to ASTM D7264 standard, flexural strength and modulus were determined using Instron 3382 Universal Testing Machine .Rectangular specimens of dimensions 100mm x12.7mm x3 mm were cut for the test. The span length was kept at 60 mm and cross head speed was maintained at 2mm/min throughout the test. Five specimens of each type were tested and their average values were considered. From the fig.4(a-b), it is observed that the flexural strength is the highest at 5% loading of nanoclay as compared to other nanocomposites. But beyond that there is a decline in flexural strength . Similarly, the modulus of the 5% nanoclay is also found to be the greatest among other percentage loading of nanoclay which is mainly attributed to the finer dispersion of nanoclay in the epoxy matrix. Composites with nanoclay loading uptil 5% shows good increasing trends of flexural strength and modulus and decreases further with increase in nanoclay.The compsoites having 5% nanoclay improve the flexural strength and modulus by 37.5% and 37.67% respectively as compared to neat/plain glass fiber reinforced polymer composites.
Fig.4. (a) Flexural Strength; (b) Flexural Modulus of nanocomposite
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3.4 Dry Abrasive Wear Dry abrasive wear test was conducted using dry abrasion tester of DUCOM TR-50. Specimens of required dimensions (76mm x 25.5mm x 3 mm) were cut according to the ASTM G65 standard. Abrasive particle of dry sand of grade AFS 60 was flown between the wheel and the desired specimen. A constant load of 25.5 N was applied with the help of lever arm and rotating wheel speed was maintained at 125 rpm. With respect to density and weight loss, the volume loss was calculated. Specific wear rate (SWR) was then calculated from the following equation SWR = ∆V/L x D (1) where ∆V is the loss in volume in mmᶟ, L is the applied load applied (N) and D is the sliding distance in (m). Fig.5 shows that the specific wear rate versus types of composite having different weight percentage of nanoclay. It is observed that at 5% loading of nanoclay has the lowest SWR as compared to other hybrid nanocomposites. As the hardness number of the specimen is more, so it is obvious that the wearing of the above mentioned specimen will be the least. Hence, the nanoclay loading of 5% gives us better results and Fig.6 (a-e) shows the different specimens subjected to dry abrasive wear test. It is observed that maximum volume loss was for 0% and 7% nanoclay content. The SWR of the nanocomposite having 5% nanoclay was reduced by 20% as compared to other composites.
Fig.5. Specific wear rate of different nanocomposites
Fig. 6. Dry Abrasive wear test of different composites corresponding to (a)0%, (b)1%, (c)3%, (d)5% and (e)7% loadings of nanoclay.
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4. Conclusion Nanoclay reinforced epoxy polymer matrix nanocomposite were fabricated and the mechanical and tribological properties were investigated. The following conclusion may be drawn. The hardness of the composites with varying percentages of nanoclay (0%, 1%, 3%, 5%, and 7% of wt.) was increased up to 5% loading of nanoclay and decreases further increase in it. The toughness of the composites which is a measure of impact energy was increased with the nanoclay content. The maximum impact energy was found to be at 5% loading of nanoclay which was found to be 40.8% more than neat epoxy glass fibre reinforced composite. The flexural strength and modulus of the nanocomposite having 5% nanoclay was increased by 37.5% and 37.67% respectively in comparison to neat epoxy based glass fibre reinforced composite. The SWR of the nanocomposite having 5% nanoclay was found to be less which indicates good wear behaviour of the material. References 1. Shetty, M. R., Vijay Kumar, K. 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