Development of Potential Composites through Natural Fiber Reinforcement

Transcription

1 Journal of Scientific & Industrial Research Vol. 74, February 2015, pp Development of Potential Composites through Natural Fiber Reinforcement V Chaudhary 1, P P Gohil 2 * and A A Shaikh 3 1 Department of Mechanical Engineering, Faculty of Technology and Engineering, Charotar University of Science and Technology, Changa , Gujarat, India *2 Department of Mechanical Engineering, Faculty of Technology and Engineering, M S University of Baroda, Vadodara, Pin , Gujarat, India 3 Department of Mechanical Engineering, S.V. National Institute of Technology, Ichchhanath, Surat , Gujarat, India Received 29 October 2012; revised 14 November 2013; accepted 24 September 2014 Fibers are best suitable material as reinforcement, which increases properties of the emerging composite materials. The use of high strength fiber leads to new advanced composites which can be used for great strength applications. Yet, the use of medium and low strength fibers available in nature are also consuming sufficient potential for various applications where high strength is not critical but it can offer a practicable range of alternative materials to appropriate conventional material. The composite materials which are more environmentally friendly, energy efficient and recyclable have great potential market. The present work studies the various types of natural fiber available for the improvement of potential composites. The paper also discusses the methodology of the development of cotton-polyester composites using filament winding technology and hand layup method. Keywords: Composites, Natural fiber, Filament winding, Hand layup method, Cotton-Polyester Composites. Introduction Composites are materials that comprise of strong load carrying materials (known as reinforcement) embedded in weaker materials (known as matrix). This structure results in a material that increases specific performance properties. The components do not disband completely and as a result normally show an interface between one another. Both reinforcing and matrix keep their physical and chemical identities; however constituents make a combination of properties that cannot be attained with either of the constituent acting alone 1. Natural Fiber Reinforcement: Classification and Countries of Origin India, gifted with a rich availability of various natural fibers listed in Fig. 1, has paid attention on the advancement of natural fiber composites mainly to discover value-added application opportunities. These natural fiber composites are companionable with wood replacements in the shelters and building sector. The growth of composites developed from various natural fibers in India is based on a bilateral strategy *Author for correspondence push4679@yahoo.com of avoiding reduction of forest resources in addition to ensure good financial revenues for the farming of natural fibers. Researchers and scientists are defining ways to get better qualities of composites so it may be tough, lightweight, long-standing, and cheap to produce. Natural fiber reinforcement is biodegradable and nonabrasive, unlike other man-made reinforcing fibers. Specific properties of some natural fibers are comparable to those of synthetic fibers used as reinforcements in composites 2-6. Natural fibers can be classified based on agricultural resources (plant fibers) and based on resources derived from animals (animal fibers). The plant fibers can be divided into various classes which are shown in Fig. 1. All above mentioned types of natural fibers in Fig.1 are available. For example, sisal fibers are widely cultivated in Tanzania and Brazil. Sisal plants are also widely grown in humid countries of Africa, the West Indies and Far East 8. China, India and Bangladesh are the major producers of jute. Now a day the worldwide production of natural fibers is around 25 million tons while in India it is 6 million tons per year 9. Flax and hemp are largely being cultivated in Europe, Russia, Canada, Argentina and India. Kenaf is a crop grown commercially in the United States 10. India is also producing 20% of world production of coir 11.

2 94 J SCI IND RES VOL 74 FEBRUARY 2015 Chemical Composition of Natural Fibers The chemical composition and the structure of plant fibers depend to a large extent on climatic conditions, age and the digestion process of the plant, which they are derived from. Component values of some of plant fibers are presented in Table 1. With the exception of cotton, the major components of natural fibers are lignin, pectin, cellulose, hemicellulose, waxes and water-soluble substances Mechanical Property of Natural Fibers The physical properties of the fibers are mainly determined by cellulose, hemicellulose and lignin. Hemicellulose and pectin are responsible for the biodegradation, moisture absorption, and thermal degradation of fiber. Lignin is thermally stable, but degrades under UV radiation. Individual fiber properties and the structure of fiber bundles can vary widely depending on the plant, part of the stem (close to the roots/close to the top), age, extraction technique, moisture content, speed of testing, history of fiber, etc. Because of so many influencing factors there is a large variation in their properties 12. The mechanical properties of natural fiber are dependent on the cellulose content in the fiber, polymerization of the cellulose and the angle of the micro fibrils 13. Fibers with greater cellulose content, greater degree of polymerization and a smaller microfibrillar angle exhibit higher tensile strength and modulus. Several studies on estimation of the mechanical properties such as density, tensile strength, elastic modulus of natural fibers have been carried out 14. Properties of natural fiber in comparison to advanced high strength fiber are depicted in Table 2. Natural Fiber Composite: Property Comparison The mechanical properties of a natural fiber composite depend on parameters like fiber length, fiber orientation, fiber strength and modulus, fiber-matrix interface. Fiber-matrix interface plays vital role in the properties of natural fiber composite. For effective load transfer a good interfacial bond is required. In addition, it improves moisture resistance and the composite properties. The mechanical properties of few of natural fiber composite with polyester matrix are given in Table 3. Fig. 1 Classification of natural fibers derived from plants 7 Potential Composite from Natural Fiber Reinforcement Composites can be classified in many ways: by their densities, by their uses, by their manufacturing methods, or other systems. For the present work, they are classified by their uses. Eight different classes are having potential for development of composite Table 1 Composition of Different Natural Fibers Component Cotton Jute flax Hemp Sisal Kenaf Coir Ramie Palm Cellulose, wt % Hemi cellulose, wt % Pectin, wt % Lignin, wt % Wax, wt % Moisture wt% Microfibrillar spiral angle

3 GOHIL et al.: DEVELOPMENT OF COMPOSITES THROUGH FIBER REINFORCEMENT 95 Table 2 Properties of some synthetic and natural fibers 15. Fibers Tensile Strength, (MPa) Tensile Modulus, (GPa) Specific Gravity Specific Strength Specific Stiffness E-glass Carbon Flax Sisal Jute Hemp Banana Coir Cotton Silk Wool Table 3 Mechanical properties of unidirectionally aligned continuous fiber composite with polyester matrix along with that of randomly oriented short fiber composites 16. Fiber (Wt %) Tensile Strength (MPa) Modulus (GPa) Flexural Strength (MPa) Flexural Modulus (GPa) Impact Strength (KJm -2 ) Unidirectional Sisal (40) Banana (30) Coir (30) Chopped random Sisal (25) Banana (25) Coir (25) Fabric Banana-cotton through natural fiber reinforcement as depicted below 18. (1) Geotextiles, (2) Filters, (3) Sorbents, (4) Structural composites, (5) Non-structural composites, (6) Moulded products, (7) Packaging, and (8) Combinations with other materials There is some overlap between these areas. For example, once a fiber web has been made, it can be directly applied as a geotextile, filter, or sorbent or can be further processed into a structural or nonstructural composite, molded product, used in packaging, or combined with other resources. Within each composite made there are opportunities to improve the performance of that composite by improving the performance of the fiber going into the composite. Many different and creative applications are available for composite cylinders and shells as depicted below. Sporting goods golf shafts, sticks, rackets Rollers, Bearings, Bushings Electrical Insulator and Components Pressure vessels Cylinder for pistons Utility poles, structural columns Filter elements fiber only Bladders Looking to the diversified potential applications of natural fiber composite, here it is decided to develop the cylinders using natural fiber reinforcement. Following section describes the development methodology for cotton-polyester cylinders. Development of Cotton-Polyester Composite: An Experimental Attempt Composite cylinder The fabrication process for composite cylinder requires dedicated filament winding machine, the existing lathe machine of workshop was used for the

4 96 J SCI IND RES VOL 74 FEBRUARY 2015 fabrication of composite cylinder. It was consider as the two axes filament-winding machine. The whole set up was prepared on lathe machine. The schematic diagram of the filament winding machine is shown in Fig. 2, which shows the basic principle used for the fabrication purpose. Here an attempt is made to make use of the knowledge of literature reviewed into the practical application. The main objective was to develop the three different cylinders of varying thickness (3 mm, 5mm and 7mm). For the materials of fabrication, number of option were available but keeping in mind the availability of materials the cotton fiber is chosen because it is easily available and moreover it is a natural fiber. The resin selected is polyester as it is also easily available and the curing can be done at room temperature. The fabrication procedure consists following four stages. The developed composite cylinders are shown in Fig. 3 (a). Stage 1- Fabrication of Required Mandrel: The mandrel is the very first critical component of the filament winding process because the final replica of Fig. 2 Schematic diagram of the filament winding experimental setup using conventional lathe machine the component to be made is depends upon the mandrel accuracy. In the present work Wood is used as the material for the mandrel. The other materials can also be used but wood is selected as it is easily available and easily machined as per requirements. The shape of mandrel was kept cylindrical; the internal diameter required for composite cylinder is kept as the outer diameter of the mandrel. After the fabrication of mandrel the mandrel is kept into the oil for some amount of time so that the surface of the mandrel becomes smooth, as it is required for the easy removal of mandrel after the curing process. The polyfilm is wrapped on the circumference of the mandrel; this also helps in easy removal of mandrel after the curing. Stage 2- Preparation of Resin mixture: In this mixture polyester resin (100 ml) and hardener and catalyst (1 ml each) were used. This is used for fiber impregnation before the fibers are wrapped on the mandrel. Stage 3- Fibers Wrapping: For the wrapping of fibers the mandrel is fixed into the chuck then the fibers from the bundle are made pass through the resin mixture and then on the rotating removable mandrel. The fiber is also passed through the pins that make the fiber straight and it reduces the amount of resin so that the greater fiber content can be achieved. Wrapping of fibers continues till the required thickness of the cylinder is achieved. Stage 4- Curing Process: This stage comes after the layers of fibers were wound onto the mandrel. In this stage the curing process is divided into two parts, first the specimen on the mandrel is left to rotate for about 2 hours at room temperature to prevent resin dropping, then after specimen is kept on the mandrel itself without rotation for about 48 hours at room temperature for the proper solidification. After solidification the specimen is pulled off the mandrel. Fig. 3 Developed Cotton-Polyester Composite; (a) cylinder (b) plate

5 GOHIL et al.: DEVELOPMENT OF COMPOSITES THROUGH FIBER REINFORCEMENT 97 Composite Plate Unidirectional Cotton-Polyester Composite plate was manufactured using hand lay-up process. For this cotton fiber of 0.5 mm diameter as reinforcement and the polyester resin was used as matrix. For curing process the Cobalt as accelerator and Methyl Ethyl Ketone Peroxide (MEKP) as binder were used with initiator in 1.5% V/V proportion. Composite plate was manufactured by combining four layers of prepregs, each have 0.8 mm thickness. A prepreg is a sheet of continuous oriented cotton fibers that have been impregnated with polyester. The curing process was carried out at room temperature and allowed to cure for 24 hours. Fig. 3 (b) shows the developed composite plate of cotton polyester composite with 3.2 mm thickness. The nominal value of fiber volume fraction was achieved as 20.45% for this material 19. Conclusion Composite technology and applications have made remarkable growth globally during the last two decades. At present, around 40,000 products of composites are in use for applications in various sectors of the industry all over the world. India and China started making use of composites more or less at the same time about 30 years ago. The growth made by china is quite amazing with using up level of about 2, 00,000 MT per year while in India it is about 30,000 MT, which requires understanding for composite products and their advantages. Commercial applications for composites have not been explored still in the country. As existing materials used in gas, oil and water supply pipelines are corrosive in nature so the better replacement can be cotton polyester composite cylinders. These composite cylinders are durable and withstand high pressure too. Also cotton polyester composite plates are used as low cost composites in the interior parts of the automotive. By designing & developing advanced composite fabricating technology would extensively increase the usage of composites. The present study has shown the opportunity and advantages of filament wound structure to replace some of the conventional shell in domestic applications as well as for industrial applications. Acknowledgment We are very much thankful to the management of Charotar University of Science and Technology for constant motivation and encouragement. 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