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Fabrication and experimental evaluation of properties with reinforcement of polyester resin with sisal fibre
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 27081–27087
www.materialstoday.com/proceedings
ICAMM_2016
Fabrication and experimental evaluation of properties with reinforcement of polyester resin with sisal fibre I.S. Phani Sushma1*, B. Vasundhar2, and N.V. Jagadeesh Varma2 1 2
Student, Department of Mechanical engineering, UCEV JNTUK, Vizianagaram, Andhra Pradesh, India
Abstract In this present work we are introducing a new concept to improve the properties by reinforcement of polyester resin with sisal fiber by changing its orientation of sisal fiber for the shielding armor. The effects of surface treatment and some mechanical properties of sisal fiber reinforced unsaturated polyester resin has been investigated. The composite laminates was cut into different sizes and shapes for mechanical testing. Universal testing machine (UTM) was used to test the flexural and tensile test. From the results of the mechanical test, it was observed that, concentrations of 10% NaOH at (2 & 5 hours), 6 % NaOH at 5 hours and 2 % NaOH at 5 hours show great improvement of the mechanical performance for tensile, flexural and impact test respectively than the other various concentrations of NaOH at different time intervals. This shows that, the extent of surface modification depends on the concentration of NaOH solution and time of treatment. The influence of orientation on tensile and flexural properties of oriented sisal fibre polyester composite is studied and results were discussed. The results show that the oriented composite has superior tensile and flexural properties when compared with randomly oriented composite. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of ICAMM-2016. Keywords: sisal fiber; polymer matrix composite; impact test
1. Introduction 1.1. Composites: A composite material is a combination two or materials (mixed and bonded) on a macroscopic scale in order to obtain an improved material properties[1] Generally composite materials are heterogeneous materials which consists of two or more solid phases and they are in intimate contact with each other on a microscopic scale. But they can be also considered as homogeneous materials on a microscopic scale because of that any portion of it will have the same physical properties. *Corresponding author Mobile No: +91- 986 63 61 374; E-mail: [email protected]
2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of ICAMM-2016.
27082
I S Phani Sushma / Materials Today: Proceedings 5 (2018) 27081–27087
1.2. Composites: A composite material is a combination two or materials (mixed and bonded) on a macroscopic scale in order to obtain an improved material properties[1]. Generally composite materials are heterogeneous materials which consists of two or more solid phases and they are in intimate contact with each other on a microscopic scale. But they can be also considered as homogeneous materials on a microscopic scale because of that any portion of it will have the same physical properties. 1.3. Polymer Matrix Composites: Most commonly polymeric matrix materials are used. Because of the reason this is twofold. Generally the mechanical properties of polymers like strength and stiffness are low compared to metals and ceramics. In order to improve the properties these are reinforced. And the processing of polymer matrix composites does not require high pressure and high temperature. Also equipment required is simpler for manufacturing polymer matrix composites. These are the reasons to polymer matrix composites developed rapidly and became popular for mechanical and structural applications. And also overall properties of the composites are superior to those of the individual components for example polymer/ceramic [3-4]. 1.4. Sisal Fiber: Sisal fiber is one of the natural fibers, which possesses high modulus and specific strength, low price, easy availability, recyclability. Using sisal fiber as reinforcement to make sisal fiber reinforced polymer composites has aroused great interest of materials scientists and engineers all over the world[5][6]. Uses of sisal in engineering field: It is used in automobiles industry with fiberglass in composite materials. Sisal fiber is used commonly in the shipping industry for lashing, mooring small craft and handling cargo. Properties of sisal fibers: Sisal fiber is highly durable with a low maintenance and minimal wear and tear. It is recyclable. Its leaves can also be treated with natural borax in order to improve fire resistance properties. It exhibits good impact and sound absorbing properties.
Fig.1 Sisal Fiber
1.5. Resin: Resin is a “solid or highly viscous substance,” which are typically convertible into polymers. Resins are generally of two kinds. Thermoplastic Thermosetting
I S Phani Sushma / Materials Today: Proceedings 5 (2018) 27081–27087
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1.6. Objective of This Invention: The present investigation concentrates on the enhanced properties of natural fiber as bullet proof and guarding element. 2.
Experimental procedure
Materials used include sisal leaves (obtained from Kaduna, Nigeria); NaOH, unsaturated polyester resin and hardener. 2.1. Sisal Fibers Extraction: The dried sisal leaves were crushed and beaten manually with a smooth edged stick until the fibers. Then the fiber are cleaned thoroughly in plenty of distilled water in order to remove dust and surplus wastes and finally air-dried. 2.2. Morphology Study: Scanning electron microscopic (SEM) photographs of untreated and alkali (NaOH) treated sisal fibers were obtained with a PhenomProX SEM at room temperature. 2.3. Alkali Treatment of Sisal Fibers: 20 grams each of the extracted sisal fibers was soaked in 2, 6 and 10 % NaOH solution for 2, 3 and 5 hours each at a temperature of 65oC under constant stirring. The fibers were then rinsed with distilled water followed by neutralization in 2 % acetic acid solution to remove the residual NaOH solution. A final rinse in distilled water till the fibers was neutral to litmus paper and then dried in open air for 4 to 5 days. With this the moisture content in the fibers were completely removed. The treated sisal fibers were labeled and packed in air tight polyethylene bags to prevent dust and dirt from coming in contact with them [7]. 2.4. Fabrication of Composites: The unsaturated polyester resin was mixed with the methyl ethyl ketone peroxide (catalyst) and cobalt accelerator. The sisal fibers were cut to size, each weighing 0.3 g. Composites laminates were obtained by impregnating 0.3 g of each of the treated and untreated sisal fiber samples with polyester matrix in a mould using the hand lay-up method at room temperature to obtain 0.65 fiber volume fractions. 2.5. Sample Preparation: Add 1.5ml of catalyst and 1.5ml of accelerator to the 100ml of resin for the solidification process as shown in fig.2. In this we are using resin as polyester and accelerator as cobalt napthanate and catalyst as methyl ethyl ketone peroxide. Above proportions are prepared and stirred in volumetric flask. Mould should be coated with gel. Transfer the solution to the respective moulds. Solidification time is 35 – 45 min. Specimen is taken from the mould for testing.
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I S Phani Sushma / Materials Today: Proceedings 5 (2018) 27081–27087
Fig 2. (a) Resin preparation (b) Mould with applied gel (c) Mould
2.6. Tensile and Flexural Testing of Composites: Tensile tests and 3-point flexural tests were conducted with a Universal testing machine (model 4202). Tensile tests were performed at a strain rate of 10 mm per min and gauge length of 140 mm according to ASTM D638-06[12]. Flexural testing was also carried out in accordance with ASTM D-790-08. A 3-point loading system was employed to determine the flexural strength of the various composites fabricated. The dimensions of the specimens in each case were 140 mm × 25 mm × 4 mm. The tensile strength at break was calculated from the equation below: Tensile strength = )ܰ( ݁ܿݎ݂݃݊݅݇ܽ݁ݎܤ/ܱ݉( ܽ݁ݎܣ݈ܽ݊݅ݐܿ݁ݏݏݎܥ݈ܽ݊݅݃݅ݎ2)
(1)
The flexural strength (F.S.) and flexural modulus of the composite specimens were determined using the following equations. Flexural Strength = 3ܲܮ/2ܾݐ2 (2) Flexural Modulus = ܲܮ3/4ܾݐ3ݓ (3) Where, L is the span length of the sample. P is the load applied; b and t are the width and thickness of the specimen respectively, w is the deflection. Tensile strength is an indication that the ability of a composite material to withstand forces that pull it apart and also the capacity of the material to stretch prior to failure [10]. 2.7. Sample Preparation with Fiber: Special moulds are prepared for reinforcement of sisal fiber in resin matrix. In this we are concentrating on orientation of the fiber. With reference to the following source an orientation of (0, 45, 90, 45, and 0) was taken for study [8]. National Conference on Recent Trends and Developments in Sustainable Green Technologies Journal of Chemical and Pharmaceutical Sciences www.jchps.com ISSN: 0974-2115. 2.8. Experimental procedure with fiber: Initially the fibers are combed and are arranged neatly as long fibers. The orientation to be followed in the composite is selected. Desired amount of fiber is taken in order to achieve the weight percentage of 50±2. Then the fibers are arranged in the particular angle as per the orientation selected in the specially designed mould. The mould consists of markings for every angle, from which we can ensure that the fibers are in the desired angle. The resin is prepared in the meantime. For every 100ml of the resin 1.5 ml of catalyst and 1.5ml of accelerator are added to it. The resin is poured over the fibers are in kept in compression moulding machine at a pressure of 170kg/cm2. The composite is left in the moulding machine for about 24 hours for curing.
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Fig 3. Specimen of sisal fiber composite
3. Results 3.1. Tensile Test: Tensile test was conducted by using Instron (Series-3382). Tensile test determine strength of the composite specimen shown in fig.3. The force needed to break the composite is measured in tensile test. Tensile test is done in universal test machine. The machine consists of two grips to hold the specimen on either side. When the machine is operated it pulls the specimen from either side until it breaks. The extent to which the specimen elongates or stretches until the breaking point can also be found out in the tensile test. The results of the tensile test are useful in determining where the composite can be used. The most common specimen is a constant rectangular cross section as per the ASTM: D3039-08, 20 mm wide and 200 mm long. Tensile test result is measured in MPa. The composites strength is depend upon many factors such as bonding between the fiber to matrix, fiber orientation and etc. The fig.1 indicates the tensile strength of different orientations by using sisal fiber reinforced composites. As mentioned in graph 1 the tensile strength of 0˚/90˚/0˚ composite has higher than the other type of composites. This might be due to the uniform stress transfer distribution between the fibers compare to the 0˚/45˚/0˚ and random type of composites. Further the most of the fibers are orientated longitudinally so as to withstand the tensile load along the length of fiber orientation.
Graph 1. Fiber orientation v/s Tensile strength
3.2. Flexural Test: The flexural test was conducted by using the Instron (Series-3382). The force required to bend beam under three point loading conditions is measured by flexural test. The results helpful in determining materials for parts that will support loads without flexing. The setup consists of a support span above which the specimen is placed and the load is applied at the centre with the help of a loading nose. The load produces three points bending at a specified rate. Commonly the specimen with the size ( as per ASTM: D790-10) 125mm×13mm×13mm. Flexural strength is measured in terms of MPa[2].
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I S Phani Sushma / Materials Today: Proceedings 5 (2018) 27081–27087
Graph 2. Fiber orientation v/s Flexural strength
Composite flexural properties were tested by using the 3 point bend test. The flexural strength of 0˚/45˚/0˚, 0˚/90˚/0˚ and random orientation is presented in graph 2. The flexural strength was higher in 0˚/45˚/0˚ (61.1 MPa). Incorporating the degrees of 0˚/45˚/0˚ for fabricating the composites gives a superior capacity to withstand compressive strength and also gives improved resistance to transverse forces [9] [10]. Further the proper interlocking between the fibers in 0˚/45˚/0˚ enhances the flexural strength of the composites. One of the tested flexural stressstrain curve is shown in fig. 4. The percentages of improvement from 0˚/90˚/0˚, random to 0˚/45˚/0˚ are 15.38% and 6.50% [11]. 4. Conclusion It was observed that the surface of the sisal fibers before treatment was filled with hemicelluloses, waxes, lignin, pectin, impurities etc. covered up by cementing materials. However, NaOH solution treatment at various percentage concentrations (2%, 6%, and 10%), and at different timing (2 hours, 3 hours and 5 hours) at 65 OC temperature carried out on the sisal fibers, removed the adhesives and impurities constituents in the fibers according to the degree of modification. This work revelled that due to the stronger bond between the polymer matrix and treated fiber the effect of surface treatment on the mechanical properties of sisal fiber reinforced composite is actually by chemical treatment. The chemical treatment of composite was removed the hemicelluloses and lignin which act as obstructions being a matrix in the natural fibers.Based on the above experiments, the following conclusions have been made: All the three type of different oriented sisal fiber polyester composites were fabricated by using the compression moulding technique. The three types of composites are 0˚/45˚/0˚, 0˚/90˚/0˚ and random orientation[11]. 50±2 wt% of fiber was maintained in all the three types of composites. The maximum increase in tensile and flexural strength was found in the oriented combination of 0˚/90˚/0˚ and 0˚/45˚/0˚. References [1] Dhakal H. N., Zhang Z. Y., Richardson M. O. W. (2007): Effect of water absorption on the mechanical properties of hemp fiber reinforced unsaturated polyester composites. Composites Science and Technology, 67, pp 1674-1683. [2] Alavudeen, N.Rajini, S.Karthikeyan, M.Thiruchitrambalam and N.Venkateshwaren “Mechanical properties of banana/kenaf fiber-reinforced hybrid polyester composites Effect of woven fabric and random orientation C.Bennet, N.Rajini, J.T.WinowlinJappes, A.Venkatesh,S.Harinarayanan and G.Vinothkumar “Effect of lamina fiber orientation on tensile and free vibration (by impluse hammer technique) properties of coconut sheath / sansevieriacylindrica hybrid composites” Advance material research. Vol.984-985, pp. 172-177, July2014 [3] Chand, N., Tiwary, R.K. and Rohatgi, P.K. (1988) Polymer composite J. Material Science, pp.23. [4] Chandra R., Rustgi R. (1998). Biodegradable Polymers: Progress in Polymer Science; Vol: 23, pp 1273-1335. [5] D.Chandramohan and K.Marimuthu “A Review on natural fibers” Academic journal. Vol-8, pp. 194, September2011. [6] P.A. Sreekumar, Kuruvilla Joseph, G.Unnikrishnan and Sabu Thomas “A Compararive Study on mechanical properties of sisal-leaf fiber-reinforced polyester composites prepared by resin transfer and compression moulding techniques” compos. Sci. technol, vol-67, pp.453-461, March 2007.
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[7] Cao, Y., Shibata, S. and Fukumoto, I. (2006). Mechanical properties of biodegradable composites reinforced with bagasse fiber before and after alkali treatments. Composites Part A. Applied Science and Manufacturing 37:423-429. [8] K.Murali Mohan Rao, K. Mohana Rao and A.V.Ratna Prasad “Fabrication and testing of natural fiber composites: Vakka, Sisal Bamboo and Banana” Mater. Des. Vol-31, pp. 508-513, Janauary 2010 [9] Shivnand, H.K., Prakash. S. Inamdar, and G Sapthagiri.. "Evaluation of tensile and flexural properties of hemp and polypropylene based natural fiber composites", 2010 2nd International Conference on Chemical Biological and Environmental Engineering, 2010 [10] S. Shibata, Y. Cao, and I. Fukumoto “Press forming of short natural fiber-reinforced biodegradable resin: Effects of fiber volume and length on flexural properties”. Polym. Test. Vol 24. Pp. 1005-1-11. 2005. [11] V.M.Fonesca, V.J.FernandesJr, L. H. de Carvalho, and J.R.M. d’Almeida “Evaluation of the mechanical properties of SisalPolyester composite as a function of the polyester matrix” J. Appl. Polym. Sci. vol-94, pp. 1209-1217, 5 November 2004. [12] V.S. Sreenivasan, D. Ravindran, V. Manikandan and R. Narayanasamy “Mechanical properties of randomly oriented short Sansevieriacylindrica fiber/polyester composites” Mater. Des. Vol-32, pp.2444–2455, 2011. [13] Ochi, S.. "Mechanical properties of kenaf fibers and kenaf/PLA composites", Mechanics of Materials, 200804.
ScienceDirect Materials Today: Proceedings 5 (2018) 27081–27087
www.materialstoday.com/proceedings
ICAMM_2016
Fabrication and experimental evaluation of properties with reinforcement of polyester resin with sisal fibre I.S. Phani Sushma1*, B. Vasundhar2, and N.V. Jagadeesh Varma2 1 2
Student, Department of Mechanical engineering, UCEV JNTUK, Vizianagaram, Andhra Pradesh, India
Abstract In this present work we are introducing a new concept to improve the properties by reinforcement of polyester resin with sisal fiber by changing its orientation of sisal fiber for the shielding armor. The effects of surface treatment and some mechanical properties of sisal fiber reinforced unsaturated polyester resin has been investigated. The composite laminates was cut into different sizes and shapes for mechanical testing. Universal testing machine (UTM) was used to test the flexural and tensile test. From the results of the mechanical test, it was observed that, concentrations of 10% NaOH at (2 & 5 hours), 6 % NaOH at 5 hours and 2 % NaOH at 5 hours show great improvement of the mechanical performance for tensile, flexural and impact test respectively than the other various concentrations of NaOH at different time intervals. This shows that, the extent of surface modification depends on the concentration of NaOH solution and time of treatment. The influence of orientation on tensile and flexural properties of oriented sisal fibre polyester composite is studied and results were discussed. The results show that the oriented composite has superior tensile and flexural properties when compared with randomly oriented composite. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of ICAMM-2016. Keywords: sisal fiber; polymer matrix composite; impact test
1. Introduction 1.1. Composites: A composite material is a combination two or materials (mixed and bonded) on a macroscopic scale in order to obtain an improved material properties[1] Generally composite materials are heterogeneous materials which consists of two or more solid phases and they are in intimate contact with each other on a microscopic scale. But they can be also considered as homogeneous materials on a microscopic scale because of that any portion of it will have the same physical properties. *Corresponding author Mobile No: +91- 986 63 61 374; E-mail: [email protected]
2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of ICAMM-2016.
27082
I S Phani Sushma / Materials Today: Proceedings 5 (2018) 27081–27087
1.2. Composites: A composite material is a combination two or materials (mixed and bonded) on a macroscopic scale in order to obtain an improved material properties[1]. Generally composite materials are heterogeneous materials which consists of two or more solid phases and they are in intimate contact with each other on a microscopic scale. But they can be also considered as homogeneous materials on a microscopic scale because of that any portion of it will have the same physical properties. 1.3. Polymer Matrix Composites: Most commonly polymeric matrix materials are used. Because of the reason this is twofold. Generally the mechanical properties of polymers like strength and stiffness are low compared to metals and ceramics. In order to improve the properties these are reinforced. And the processing of polymer matrix composites does not require high pressure and high temperature. Also equipment required is simpler for manufacturing polymer matrix composites. These are the reasons to polymer matrix composites developed rapidly and became popular for mechanical and structural applications. And also overall properties of the composites are superior to those of the individual components for example polymer/ceramic [3-4]. 1.4. Sisal Fiber: Sisal fiber is one of the natural fibers, which possesses high modulus and specific strength, low price, easy availability, recyclability. Using sisal fiber as reinforcement to make sisal fiber reinforced polymer composites has aroused great interest of materials scientists and engineers all over the world[5][6]. Uses of sisal in engineering field: It is used in automobiles industry with fiberglass in composite materials. Sisal fiber is used commonly in the shipping industry for lashing, mooring small craft and handling cargo. Properties of sisal fibers: Sisal fiber is highly durable with a low maintenance and minimal wear and tear. It is recyclable. Its leaves can also be treated with natural borax in order to improve fire resistance properties. It exhibits good impact and sound absorbing properties.
Fig.1 Sisal Fiber
1.5. Resin: Resin is a “solid or highly viscous substance,” which are typically convertible into polymers. Resins are generally of two kinds. Thermoplastic Thermosetting
I S Phani Sushma / Materials Today: Proceedings 5 (2018) 27081–27087
27083
1.6. Objective of This Invention: The present investigation concentrates on the enhanced properties of natural fiber as bullet proof and guarding element. 2.
Experimental procedure
Materials used include sisal leaves (obtained from Kaduna, Nigeria); NaOH, unsaturated polyester resin and hardener. 2.1. Sisal Fibers Extraction: The dried sisal leaves were crushed and beaten manually with a smooth edged stick until the fibers. Then the fiber are cleaned thoroughly in plenty of distilled water in order to remove dust and surplus wastes and finally air-dried. 2.2. Morphology Study: Scanning electron microscopic (SEM) photographs of untreated and alkali (NaOH) treated sisal fibers were obtained with a PhenomProX SEM at room temperature. 2.3. Alkali Treatment of Sisal Fibers: 20 grams each of the extracted sisal fibers was soaked in 2, 6 and 10 % NaOH solution for 2, 3 and 5 hours each at a temperature of 65oC under constant stirring. The fibers were then rinsed with distilled water followed by neutralization in 2 % acetic acid solution to remove the residual NaOH solution. A final rinse in distilled water till the fibers was neutral to litmus paper and then dried in open air for 4 to 5 days. With this the moisture content in the fibers were completely removed. The treated sisal fibers were labeled and packed in air tight polyethylene bags to prevent dust and dirt from coming in contact with them [7]. 2.4. Fabrication of Composites: The unsaturated polyester resin was mixed with the methyl ethyl ketone peroxide (catalyst) and cobalt accelerator. The sisal fibers were cut to size, each weighing 0.3 g. Composites laminates were obtained by impregnating 0.3 g of each of the treated and untreated sisal fiber samples with polyester matrix in a mould using the hand lay-up method at room temperature to obtain 0.65 fiber volume fractions. 2.5. Sample Preparation: Add 1.5ml of catalyst and 1.5ml of accelerator to the 100ml of resin for the solidification process as shown in fig.2. In this we are using resin as polyester and accelerator as cobalt napthanate and catalyst as methyl ethyl ketone peroxide. Above proportions are prepared and stirred in volumetric flask. Mould should be coated with gel. Transfer the solution to the respective moulds. Solidification time is 35 – 45 min. Specimen is taken from the mould for testing.
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I S Phani Sushma / Materials Today: Proceedings 5 (2018) 27081–27087
Fig 2. (a) Resin preparation (b) Mould with applied gel (c) Mould
2.6. Tensile and Flexural Testing of Composites: Tensile tests and 3-point flexural tests were conducted with a Universal testing machine (model 4202). Tensile tests were performed at a strain rate of 10 mm per min and gauge length of 140 mm according to ASTM D638-06[12]. Flexural testing was also carried out in accordance with ASTM D-790-08. A 3-point loading system was employed to determine the flexural strength of the various composites fabricated. The dimensions of the specimens in each case were 140 mm × 25 mm × 4 mm. The tensile strength at break was calculated from the equation below: Tensile strength = )ܰ( ݁ܿݎ݂݃݊݅݇ܽ݁ݎܤ/ܱ݉( ܽ݁ݎܣ݈ܽ݊݅ݐܿ݁ݏݏݎܥ݈ܽ݊݅݃݅ݎ2)
(1)
The flexural strength (F.S.) and flexural modulus of the composite specimens were determined using the following equations. Flexural Strength = 3ܲܮ/2ܾݐ2 (2) Flexural Modulus = ܲܮ3/4ܾݐ3ݓ (3) Where, L is the span length of the sample. P is the load applied; b and t are the width and thickness of the specimen respectively, w is the deflection. Tensile strength is an indication that the ability of a composite material to withstand forces that pull it apart and also the capacity of the material to stretch prior to failure [10]. 2.7. Sample Preparation with Fiber: Special moulds are prepared for reinforcement of sisal fiber in resin matrix. In this we are concentrating on orientation of the fiber. With reference to the following source an orientation of (0, 45, 90, 45, and 0) was taken for study [8]. National Conference on Recent Trends and Developments in Sustainable Green Technologies Journal of Chemical and Pharmaceutical Sciences www.jchps.com ISSN: 0974-2115. 2.8. Experimental procedure with fiber: Initially the fibers are combed and are arranged neatly as long fibers. The orientation to be followed in the composite is selected. Desired amount of fiber is taken in order to achieve the weight percentage of 50±2. Then the fibers are arranged in the particular angle as per the orientation selected in the specially designed mould. The mould consists of markings for every angle, from which we can ensure that the fibers are in the desired angle. The resin is prepared in the meantime. For every 100ml of the resin 1.5 ml of catalyst and 1.5ml of accelerator are added to it. The resin is poured over the fibers are in kept in compression moulding machine at a pressure of 170kg/cm2. The composite is left in the moulding machine for about 24 hours for curing.
I S Phani Sushma / Materials Today: Proceedings 5 (2018) 27081–27087
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Fig 3. Specimen of sisal fiber composite
3. Results 3.1. Tensile Test: Tensile test was conducted by using Instron (Series-3382). Tensile test determine strength of the composite specimen shown in fig.3. The force needed to break the composite is measured in tensile test. Tensile test is done in universal test machine. The machine consists of two grips to hold the specimen on either side. When the machine is operated it pulls the specimen from either side until it breaks. The extent to which the specimen elongates or stretches until the breaking point can also be found out in the tensile test. The results of the tensile test are useful in determining where the composite can be used. The most common specimen is a constant rectangular cross section as per the ASTM: D3039-08, 20 mm wide and 200 mm long. Tensile test result is measured in MPa. The composites strength is depend upon many factors such as bonding between the fiber to matrix, fiber orientation and etc. The fig.1 indicates the tensile strength of different orientations by using sisal fiber reinforced composites. As mentioned in graph 1 the tensile strength of 0˚/90˚/0˚ composite has higher than the other type of composites. This might be due to the uniform stress transfer distribution between the fibers compare to the 0˚/45˚/0˚ and random type of composites. Further the most of the fibers are orientated longitudinally so as to withstand the tensile load along the length of fiber orientation.
Graph 1. Fiber orientation v/s Tensile strength
3.2. Flexural Test: The flexural test was conducted by using the Instron (Series-3382). The force required to bend beam under three point loading conditions is measured by flexural test. The results helpful in determining materials for parts that will support loads without flexing. The setup consists of a support span above which the specimen is placed and the load is applied at the centre with the help of a loading nose. The load produces three points bending at a specified rate. Commonly the specimen with the size ( as per ASTM: D790-10) 125mm×13mm×13mm. Flexural strength is measured in terms of MPa[2].
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Graph 2. Fiber orientation v/s Flexural strength
Composite flexural properties were tested by using the 3 point bend test. The flexural strength of 0˚/45˚/0˚, 0˚/90˚/0˚ and random orientation is presented in graph 2. The flexural strength was higher in 0˚/45˚/0˚ (61.1 MPa). Incorporating the degrees of 0˚/45˚/0˚ for fabricating the composites gives a superior capacity to withstand compressive strength and also gives improved resistance to transverse forces [9] [10]. Further the proper interlocking between the fibers in 0˚/45˚/0˚ enhances the flexural strength of the composites. One of the tested flexural stressstrain curve is shown in fig. 4. The percentages of improvement from 0˚/90˚/0˚, random to 0˚/45˚/0˚ are 15.38% and 6.50% [11]. 4. Conclusion It was observed that the surface of the sisal fibers before treatment was filled with hemicelluloses, waxes, lignin, pectin, impurities etc. covered up by cementing materials. However, NaOH solution treatment at various percentage concentrations (2%, 6%, and 10%), and at different timing (2 hours, 3 hours and 5 hours) at 65 OC temperature carried out on the sisal fibers, removed the adhesives and impurities constituents in the fibers according to the degree of modification. This work revelled that due to the stronger bond between the polymer matrix and treated fiber the effect of surface treatment on the mechanical properties of sisal fiber reinforced composite is actually by chemical treatment. The chemical treatment of composite was removed the hemicelluloses and lignin which act as obstructions being a matrix in the natural fibers.Based on the above experiments, the following conclusions have been made: All the three type of different oriented sisal fiber polyester composites were fabricated by using the compression moulding technique. The three types of composites are 0˚/45˚/0˚, 0˚/90˚/0˚ and random orientation[11]. 50±2 wt% of fiber was maintained in all the three types of composites. The maximum increase in tensile and flexural strength was found in the oriented combination of 0˚/90˚/0˚ and 0˚/45˚/0˚. References [1] Dhakal H. N., Zhang Z. Y., Richardson M. O. W. (2007): Effect of water absorption on the mechanical properties of hemp fiber reinforced unsaturated polyester composites. Composites Science and Technology, 67, pp 1674-1683. [2] Alavudeen, N.Rajini, S.Karthikeyan, M.Thiruchitrambalam and N.Venkateshwaren “Mechanical properties of banana/kenaf fiber-reinforced hybrid polyester composites Effect of woven fabric and random orientation C.Bennet, N.Rajini, J.T.WinowlinJappes, A.Venkatesh,S.Harinarayanan and G.Vinothkumar “Effect of lamina fiber orientation on tensile and free vibration (by impluse hammer technique) properties of coconut sheath / sansevieriacylindrica hybrid composites” Advance material research. Vol.984-985, pp. 172-177, July2014 [3] Chand, N., Tiwary, R.K. and Rohatgi, P.K. (1988) Polymer composite J. Material Science, pp.23. [4] Chandra R., Rustgi R. (1998). Biodegradable Polymers: Progress in Polymer Science; Vol: 23, pp 1273-1335. [5] D.Chandramohan and K.Marimuthu “A Review on natural fibers” Academic journal. Vol-8, pp. 194, September2011. [6] P.A. Sreekumar, Kuruvilla Joseph, G.Unnikrishnan and Sabu Thomas “A Compararive Study on mechanical properties of sisal-leaf fiber-reinforced polyester composites prepared by resin transfer and compression moulding techniques” compos. Sci. technol, vol-67, pp.453-461, March 2007.
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