Mechanical property evaluation of sisal–jute–glass fiber reinforced polyester composites

Mechanical property evaluation of sisal–jute–glass fiber reinforced polyester composites

Composites: Part B 48 (2013) 1–9 Contents lists available at SciVerse ScienceDirect Composites: Part B journal homepage: www.elsevier.com/locate/com...

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Composites: Part B 48 (2013) 1–9

Contents lists available at SciVerse ScienceDirect

Composites: Part B journal homepage: www.elsevier.com/locate/compositesb

Mechanical property evaluation of sisal–jute–glass fiber reinforced polyester composites M. Ramesh a, K. Palanikumar b,⇑, K. Hemachandra Reddy c a

Jawaharlal Nehru Technological University, Anantapur, Andhra Pradesh, India Department of Mechanical Engineering, Sri Sai Ram Institute of Technology, Chennai, Tamil Nadu, India c Department of Mechanical Engineering, Jawaharlal Nehru Technological University, Anantapur, Andhra Pradesh, India b

a r t i c l e

i n f o

Article history: Received 6 September 2012 Accepted 13 December 2012 Available online 20 December 2012 Keywords: A. Hybrid A. Polymer–matrix composites (PMCs) B. Mechanical properties D. Mechanical testing Jute–sisal–glass fiber-reinforced polyester composite

a b s t r a c t The composite materials are replacing the traditional materials, because of its superior properties such as high tensile strength, low thermal expansion, high strength to weight ratio. The developments of new materials are on the anvil and are growing day by day. Natural fiber composites such as sisal and jute polymer composites became more attractive due to their high specific strength, lightweight and biodegradability. Mixing of natural fiber with Glass-Fiber Reinforced Polymers (GFRPs) are finding increased applications. In this study, sisal–jute–glass fiber reinforced polyester composites is developed and their mechanical properties such as tensile strength, flexural strength and impact strength are evaluated. The interfacial properties, internal cracks and internal structure of the fractured surfaces are evaluated by using Scanning Electron Microscope (SEM). The results indicated that the incorporation of sisal–jute fiber with GFRP can improve the properties and used as a alternate material for glass fiber reinforced polymer composites. Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction Glass Fiber Reinforced Polymers (GFRPs) is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. Fiber glass is a lightweight, strong, and robust material used in different industries due to their excellent properties. Although strength properties are somewhat lower than carbon fiber and it is less stiff, the material is typically far less brittle, and the raw materials are much less expensive [1]. Its bulk strength and weight properties are very favorable when compared to metals, and it can be easily formed using molding processes [2]. Now a days natural fibers such as sisal and jute fiber composite materials are replacing the glass and carbon fibers owing to their easy availability and cost [3]. The use of natural fibers is improved remarkably due to the fact that the field of application is improved day by day especially in automotive industries. Several researches have been taken place in this direction. Silva et al. [4] have developed the natural fibers/castor oil polyurethane composites and tested the fracture toughness. They have achieved the best fracture toughness performance for sisal fiber composites. The thermophysical properties of natural fiber reinforced polyester composites is carried out by ⇑ Corresponding author. E-mail addresses: [email protected] (M. Ramesh), palanikumar_k@yahoo. com, [email protected] (K. Palanikumar), [email protected] (K.H. Reddy). 1359-8368/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.compositesb.2012.12.004

Idicula et al. [5]. They have indicated that the natural fiber with glass allows a significantly better heat transport ability for the composites. Cicala et al. [6] have studied the properties and performance of various hybrid glass/natural fiber composites for the applications in curved pipes. Natural fibers are lighter and cheaper, but they have low mechanical properties than glass fibers. The use of hybrid fibers may solve this issue. Most of the studies on natural fibers are concerned with single reinforcement. The addition of natural fiber to the glass fiber can make the composite hybrid which is comparatively cheaper and easy to use. Panthapulakkal and Sain [7] studied the mechanical and thermal properties of hemp/glass fiber–polypropylene (PP) composite materials. They have observed that the use of hybrid composite material enhance the flexural and impact properties. In addition they have observed that the addition of glass fiber into hemp–PP composites resulted in improved thermal properties as well as the water resistance of the composites. Arbelaiz et al. [8] have developed flax fiber/polypropylene composites and studied the influence of fiber/matrix modification and glass fiber hybridization. They have reported that the tensile strength and modulus of hybrid glass/flax–PP composites depend on the glass/flax ratio. Thwe and Liao [9] have studied the durability of bamboo/glass fiber reinforced polymer matrix hybrid composites. They have studied the properties such as tensile strength and elastic modulus of bamboo fiber reinforced polypropylene

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(BFRP) and bamboo glass fiber reinforced polypropylene hybrid composites. They have indicated that the tensile strength and elastic modulus decreased after ageing. The tensile strength of the jute fiber is directly proportional to the cross sectional area of the fiber [10] and delamination of layer is possible [11]. Sisal–jute–GFRP hybrid composites are environment friendly and user friendly materials [12] and has very good elastic properties [13]. The method of disposal of GFRP and their recycling have been the serious issue [14,15] and the natural fiber composites plays very important role in the environmental situation and variety of applications [16]. The incorporation of natural fiber with GFRP improves the tensile, flexural and impact strength of the materials [17] and placing the GFRP layers at the ends possess good mechanical strength [18]. Natural fibers are chosen as reinforcement because they can reduce the tool wear when processing, respiratory irritation and serving as alternatives for artificial fiber composites in the increasing global energy crisis and ecological risks [19]. In the present study the mechanical properties of sisal–jute–glass fiber reinforced composite materials is studied. The sisal–jute–GFRP composite materials are manufactured by hand lay-up process. The properties such as tensile, flexural and impact are studied and presented in detail. The results indicated that the addition of sisal and jute in the glass fiber composite materials make the composite hybrid and it improves the properties. 2. Experimental 2.1. Materials In this present investigation Sisal (Agave sisalana), Jute (Corchorus oliotorus) and GFRP fibers are used for fabricating the composite specimen. The sisal and jute fibers are obtained from Dharmapuri District, Tamil Nadu, India. Isothalic polyester resin and the catalyst Methyl Ethyl Ketone Peroxide (MEKP) are obtained from M/s. Sakthi fibre glass Ltd., Chennai, India. The accelerator used for the investigation is Cobalt Napthanate and is added as 1% with the resin and the catalyst. The Glass-Fiber Reinforced Polymers (GFRPs) used for the fabrication is of unidirectional mat having 300gsm. 2.1.1. Natural fiber In the last two decades, there has been a dramatic increase in the use of natural fibers such as fiber extraction from sisal, jute, coir, flax, hemp, pineapple and banana for making a new environment friendly and biodegradable composite materials (somehow these composites are called ‘‘Green Composites’’). Recent studies in natural fiber composites offer significant improvement in materials from renewable sources with enhanced support for global sustainability. These natural fiber composites possess high/moderate strength, thermal stability when they are recyclable, but the problems of using pure biodegradable polymers are their low strength and transition temperature. Table 1 shows the physical properties of sisal and jute fibers.

Table 1 Physical properties of sisal and jute fiber. Physical property

Sisal fiber

Jute fiber

Density (g/cm3) Elongation at break (%) Cellulose content (%) Lignin content (%) Tensile strength (MPa) Young’s modulus (GPa) Diameter (lm) Lumen size (lm)

1.41 6–7 60–65 10–14 350–370 12.8 205–230 11

1.4 1.8 50–57 8–10 400–800 30-Oct 160–185 12

2.1.2. Sisal fiber Sisal fibers are extracted from the leaves of sisal plant. The fibers are extracted through hand extraction machine composed of either serrated or non serrated knives. The peel is clamped between the wood plank and knife and hand-pulled through, removing the resinous material. The extracted fibers are sun-dried which whitens the fiber. Once dried, the fibers are ready for knotting. A bunch of fibers are mounted or clamped on a stick to facilitate segregation. Each fiber is separated according to fiber sizes and grouped accordingly. To knot the fiber, each fiber is separated and knotted to the end of another fiber manually. The separation and knotting is repeated until bunches of unknotted fibers are finished to form a long continuous strand. This Sisal fiber can be used for making variety of products. 2.1.3. Jute fiber Jute take nearly 3 months, to grow to a height of 12–15 ft, during season and then cut & bundled and kept immersed in water for ‘‘Retting’’ process, where the inner stem and outer, gets separated and the outer plant gets ‘individualized’, to form a Fiber. Then the plant get separated and washed to remove dust from the plant. The fiber after drying is taken to Jute mills, for getting converted to Jute yarn and Hessian. From the Jute, various lifestyle products are being produced and diversified into various forms, due to R&D support and also due the support by Government Organizations. 2.1.4. Glass-fiber reinforced polymer Glass-fiber reinforced plastic, or GFRP is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. Fiberglass is a lightweight, extremely strong, and robust material. Although strength properties are somewhat lower than carbon fiber and it is less stiff, the material is typically far less brittle, and the raw materials are much less expensive. Its bulk strength and weight properties are also very favorable when compared to metals, and it can be easily formed using molding processes. The plastic matrix may be epoxy, a thermosetting plastic (most often polyester or vinylester) or thermoplastic. Common uses of fiberglass include boats, automobiles, baths, hot tubs, water tanks, roofing, pipes, and external door skins. 2.2. Preparation of composite specimen The composite materials used for the present investigation is fabricated by hand layup process. Chopped sisal and jute fibers of 30 mm length were used to prepare the specimen. The composite specimen consists of total five layers in which glass fiber layers are fixed in top middle and bottom of the specimen. Second and fourth layers are filled by natural fibers such as sisal and jute. The layers of fibers are fabricated by adding the required amount of polyester resin. Initially the glass fibers polymer, jute fiber, sisal fiber are dried in sun light to remove the moisture. The glass fiber is mounted on the table. The glass fiber reinforced polymer is then completely filled with polyester resin. The resin got mixed with glass fiber reinforced polymer, which may tend to dry up within 15–20 min. Before the resin gets dried, the second layer of natural fiber is mounted over the glass fiber reinforced polymer. The process is repeated for jute fiber also. The polyester resin applied is distributed to the entire surface by means of a roller. The air gaps formed between the layers during the processing are gently squeezed out. The processed composite is pressed hard and the excess resin is removed and dried. Finally these specimens are taken to the hydraulic press to force the air gap to remove any excess air present in between the fibers and resin, and then kept for several hours to get the perfect samples. After the composite material get hardened completely, the composite material is taken out from

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the hydraulic press and rough edges are neatly cut and removed as per the required dimensions.

Sisal-Jute GFRP 2.3. Mechanical testing 2.3.1. Tensile test The hybrid composite material fabricated is cut into required dimension using a saw cutter and the edges finished by using emery paper for mechanical testing. The tensile test specimen is prepared according to the ASTM D638 standard. The dimensions, gauge length and cross-head speeds are chosen according to the ASTM D638 standard. A tensile test involves mounting the specimen in a machine and subjecting it to the tension. The testing process involves placing the test specimen in the testing machine and applying tension to it until it fractures. The tensile force is recorded as a function of the increase in gauge length. During the application of tension, the elongation of the gauge section is recorded against the applied force. The tensile test is performed on the Universal Testing Machine (UTM) Make FIE (Model: UTN 40, S.No. 11/98-2450). There are three different kind of specimen are prepared according to the fibers used. The first specimen consists of sisal–jute–GFRP fibers. The second specimen consists of sisal–GFRP and the third specimen consists of jute–GFRP fibers. The fabricated specimen for tensile test is presented in Fig. 1. The experiments are repeated for several times and the average values are used for discussion.

Sisal-GFRP

Jute-GFRP

Fig. 2. Flexural test specimen.

3. Results and discussion The use of composite materials in the different fields is increasing day by day due to their improved properties. Engineers and Scientists are working together for number of years for finding the alternative solution for the high solution materials. In the present study natural fibers are added to the glass fiber reinforced composite materials and their effect on mechanical properties is evaluated and their properties are compared. The test results for the Tensile, Flexural and Impact testing for the three varieties of the hybrid composite samples are presented in Table 2. 3.1. Tensile properties

2.3.2. Flexural test The flexural specimens are prepared as per the ASTM D790 standards. The 3-point flexure test is the most common flexural test for composite materials. Specimen deflection is measured by the crosshead position. Test results include flexural strength and displacement. The testing process involves placing the test specimen in the universal testing machine and applying force to it until it fractures and breaks. The specimen used for conducting the flexural test is presented in Fig. 2. The tests are carried out at a condition of 23 ± 2 °C and an average relative humidity of 50%.

2.3.3. Impact test The impact test specimens are prepared according to the required dimension following the ASTM-A370 standard. During the testing process, the specimen must be loaded in the testing machine and allows the pendulum until it fractures or breaks. Using the impact test, the energy needed to break the material can be measured easily and can be used to measure the toughness of the material and the yield strength. The effect of strain rate on fracture and ductility of the material can be analyzed by using the impact test. The different specimens used for impact testing is presented in Fig. 3.

Sisal-Jute- GFRP

The different composite specimen samples are tested in the universal testing machine (UTM) and the samples are left to break till the ultimate tensile strength occurs. Stress–strain curve is plotted for the determination of ultimate tensile strength and elastic modulus. The sample graph generated directly from the machine for tensile test with respect to load and displacement for sisal–jute– GFRP is presented in Fig. 4. The load with respect to the displacement for different combination of composite specimen is presented in Fig. 5. The results indicated that jute–GFRP specimen gives better tensile strength then the other two types of composites considered. The addition of sisal fibers shows comparatively low tensile strength than the other composites considered. The sisal–jute–GFRP hybrid composites perform better than the sisal fibers. The comparative results of the different composite specimen tested are presented in Fig. 6. The ultimate tensile strength (UTS) of the sisal–GFRP composite, jute–GFRP composite and sisal–jute–GFRP composite are in the range of 176.20 MPa, 229.54 MPa and 200 MPa respectively. The results indicated that the jute–GFRP composites outperformed the other types of composites tested. Fig. 7 shows the sample stress–strain curve obtained from the universal testing machine when the samples are tested and Fig. 8 gives the stress–strain curve for the different composite materials tested. The results indicate the same trend as that of the load vs displacement curve. From the results, it can be asserted that the jute–GFRP composites are performing well compared to the other type of fibers used. 3.2. Flexural properties

Sisal-GFRP

Jute-GFRP

Fig. 1. Tensile test specimen.

Fig. 9 shows the sample graph of flexural strength observed for the sisal–jute–GFRP composites. The result indicated that the displacement increases with the increase of applied load up to around 3000 N, after that, it tends to decrease, i.e., breaking takes place. The maximum displacement observed is 14.2 mm. Fig. 10 shows the load vs the displacement graph for different composites tested. The results indicated that the displacement increases with the

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Jute-GFRP

Sisal-GFRP

Sisal-Jute-GFRP

Fig. 3. Impact test specimen.

Table 2 Mechanical properties of different composite samples. Sample

Tensile strength (Mpa)

Flexural load (kN)

Displacement, (mm)

Impact strength (Joules)

Glass fiber + sisal fiber composite Glass fiber + jute fiber composite Glass fiber + jute fiber + sisal fiber composite

176.20 229.54 200.00

2.3 2.1 3.0

11.2 12.3 14.2

18 10 12

Fig. 4. Sample graph generated from the machine for load vs displacement for tensile test of sisal–jute–GFRP composite.

Fig. 5. Load vs displacement curve for tensile test.

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compared to other types composites tested followed by jute–GFRP composites. The average values observed for different composites is presented in Fig. 13. From the figure, it is asserted that the sisal– jute–GFRP composites flexural load carrying capacity is better than other composites tested. Sisal–jute–GFRP composites are capable of taking of the flexural loan up to 3 kN whereas jute–GFRP composites are capable of taking only 2.1 kN. The sisal–GFRP composites shows the performance in between jute–GFRP composites and sisal–jute–GFRP composites and are capable of taking the flexural load up to 2.3 kN. Fig. 6. Tensile load comparison of different composite materials.

increase of load. After the 14.2 mm displacement, there is a breaking exist. The results indicated that sisal–jute–GFRP shows better result than the other type of composites tested. The stress strain curve observed for sisal–jute–GFRP composites specimen is shown if Fig. 11. The result indicated that the strain increases proportional up to 13 N/mm2 after that it tends to reduce. The breaking occur after the strain rate of 35.8. The comparative evaluation of the stress strain rate observed for flexural/compression test is presented in Fig. 12. From the graph, it has been noticed that sisal–jute–GFRP composites is performing well when

3.3. Impact properties For analyzing the impact capability of the different specimens an impact test is carried out. The impact test carried out for the present investigation is Charpy impact test. The energy loss is found out on the reading obtained from the Charpy impact machine. The impact response in jute–GFRP composites reflects a failure process involving crack initiation and growth in the resin matrix, fiber breakage and pullout, delaminating and disbanding. The results of Charpy impact test is presented in Fig. 14. The results indicated that the maximum impact strength is obtained for sisal–GFRP composites followed by sisal–jute–GFRP composites.

Fig. 7. Sample graph generated from the machine for stress vs strain for tensile test of sisal–jute–GFRP composite.

Fig. 8. Stress vs strain curve for tensile test.

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Fig. 9. Sample graph generated from the machine for load vs displacement for flexural test of sisal–jute–GFRP composite.

Fig. 10. Load vs displacement curve for compression test.

Fig. 11. Sample graph generated from the machine for stress vs strain for flexural test of sisal–jute–GFRP composite.

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Fig. 12. Stress vs strain curve for compression test.

Fig. 13. Flexural load comparison of different composite materials.

Jute–GFRP composites does not perform well when compared to the other composites specimen tested. 3.4. Scanning electron microscopy (SEM) analysis The surface characteristics of the composite material used for the investigation is studied through scanning electron microscopy. The cross sectional view of the fabricated composite material consisting of sisal + jute + GFRP is presented in Fig. 15. The Scanning Electron Microscope (SEM) images are taken to observe the interfacial properties, internal cracks and internal structure of the fractured surfaces of the composite materials. All the specimens are coated with conducting material before observing the surfaces through SEM. The scanning electron image

observed for the sisal–jute–GFRP composite material subjected to tensile test is presented in Fig. 16. Fig. 16 shows the fractured surface, void formed and discontinuity in the specimen. Fig. 17 shows the SEM image for the sisal–jute–GFRP composite material which subjected to flexural test. The figure shows the fracture in the fiber bundle and incomplete distribution of the fiber and matrix in the composite material. The SEM image for the Jute–GFRP composites material which subjected to tensile load is presented in Fig. 18. Figure clearly shows the breakage of fibers in the composite materials. The SEM image for the sisal–jute–GFRP composite material which subjected to impact test is presented in Fig. 19. During the impact of the specimen, the composite material is disintegrated in the breaking point and is shown in figure.

Fig. 14. Impact load comparison of different composite materials.

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Glass fibers

Fractured surface of jute fiber Fig. 15. SEM image of sisal–jute–GFRP composite material (cross sectional view).

Fig. 18. SEM image of jute–GFRP composite material after tensile test.

Fractured surface after impact test

Fractured surface

Void formed in the fractured surface Fiber breakage

Fig. 16. SEM image of sisal–jute–GFRP composite material after tensile test. Fig. 19. SEM image of sisal–GFRP composite material after impact test.

 The jute and sisal mixture composite sample is capable having maximum flexural strength with a 14.2 mm displacement and 3.00 kN load.  The maximum impact strength is obtained for the sisal fiber composite and has the value of 18.67 joules.  The internal structure and internal cracks and breaks are observed for the broken surfaces of the tested composite samples using Scanning Electron Microscope.

Fractured surface

Incomplete distribution of fiber and matrix

Fig. 17. SEM image of sisal–jute–GFRP composite material after flexural test.

4. Conclusions The sisal/GFRP, jute/GFRP, sisal/jute/GFRP composite samples are fabricated. The hybrids composite are subjected to mechanical testing such as tensile, flexural and impact test. Based on the results, the following conclusions are drawn:  The results indicated that the jute composite material shows maximum tensile strength and can hold the strength up to 229.54 MPa.

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