Our work mainly focuses on converting waste material into raw material and to increase the strength of the fiber ..... Dr .A.V. S. Jaya Annapurna, Asst. Prof, CSS.
International Journal of Advanced Engineering Research and Studies
E-ISSN2249–8974
Research Article
TENSILE BEHAVIOR OF BANYAN TREE FIBER REINFORCED COMPOSITES 1
T. Vijaya Kumar, 2Dr. K. V. Ramana, 3Dr. R B Chowdary
Address for Correspondence 1
Associate Professor, Department of Mechanical Engineering, K L University, Vaddeswaram, Guntur Dist , AP, 2 Dean (R&D), Mechanical Engg. Dept., K L University 3 Professor, Department of Mechanical Engineering, SRK Institute of Technology, Vijayawada ABSTRACT Our work mainly focuses on converting waste material into raw material and to increase the strength of the fiber reinforced polymer composite. The study has been carried out in view of highlighting advantages of natural fibers over synthetic fibers. In this work polyester is used as a matrix and banyan tree fiber is used as a reinforcing material. Tensile test specimen is made as per ASTM D638 I. Material properties of the composite have been studied with the help of different percentage weight ratios of matrix to fiber. Also the strength of composite is estimated with the variation of fiber length. In this paper methodology of conducting the fiber preparation of mould and composite have been presented. KEYWORDS: Natural fiber, Polyester, Banyan tree fiber, Tensile test specimen.
1 INTRODUCTION The increased environmental awareness and consciousness throughout the world has developed an ever increasing interest in natural fibres and its applications in various fields. Natural fibres are now considered as serious alternative to synthetic fibres for use in various fields1 .The use of natural fibers as reinforcing materials in both thermoplastic and thermoset matrix composites provide positive environmental benefits with respect to ultimate disposability and best utilization of raw materials. The advantages of natural fibers over traditional reinforcing materials such as glass fiber, carbon fiber etc have their specific strength properties2, easy availability, light weight, ease of separation, enhanced energy recovery, high toughness, non-corrosive nature, low density, low cost, good thermal properties, reduced tool wear, reduced skin and respiratory irritation, less abrasion to processing equipment, renewability and biodegradability. It has been observed that natural fiber reinforced composites have properties similar to traditional synthetic fiber reinforced composites. Natural fiber composites have been studied and reviewed by a number of researchers3 (Dufresne 1997; Dufresne and Vignon 1998; Mao et al 2000; Kaith et al 2003; Nakagaito et al 2004, 2005; Bhatnagar and Sain 2005). During the past decade, a number of significant industries such as the automotive, construction or packaging industries have shown massive interest in the progress of new bio composite materials. All these properties have made natural fibers very attractive for various industries currently engaged in searching for new and alternate products to synthetic fiber reinforced composites. The properties of natural fibers can vary depending on the source, age and separating techniques of the fibers. Ficus benghalensis, an annual fiber plant, has been found to be an important source of fibers for a number of applications since good olden days. The banyan fiber has high potential as a reinforcing fiber in polymer composites. Banyan tree is a common home and office housetree, but in the wild forests, it’s a giant tree of Indian jungles. Banyan tree starts out life as an ephiphyte growing on another tree where some fig-eating bird deposited a seed. Banyan tree can get 100 inch tall and, with its massive limbs supported by prop roots, spread over an area of IJAERS/Vol. I/ Issue II/January-March, 2012/256-258
several acres. A famous banyan tree near Poona, India, is said to measure a half mile around its perimeter and be capable of sheltering 2000 people. The banyan tree is native to India, Sri Lanka and Pakistan. The literature review has shown scanty information on the application of this fiber as reinforcing material in the polymer composites. Keeping in view the easy availability of this new fiber a comprehensive research work3 has been initiated in our laboratory on synthesis and study of properties of banyan tree fiber reinforced polyester resin matrix based composites. Hence the objective of the present paper is to instigate the tensile properties of banyan tree fiber reinforced polyester composites. Unsaturated polyester resin has been chosen as the matrix material because it is relatively cheap, having lower shrinkage and can be moulded at room temperature. Accordingly, various percentage volumes of banyan fiber have been combined with an unsaturated polyester resin to produce banyan fiber reinforced polyester composites, and the extraction of fibres, testing of specimens and the resulting composite properties such as tensile strength, impact strength were reported. Polymer matrix composite (PMC) is a material consisting of polymer (resin) matrix combined with a fibrous reinforcing dispersed phase. PMC’s are very popular due to their cost effective and simple fabrication methods. Use of non reinforced polymers as structure materials is limited by low level of their mechanical properties: tensile strength of one of the strongest polymers-epoxy resin4 is 2000 Psi (140 Mpa). In addition to relatively low strength, polymer materials possess low impact resistance. Reinforcement of polymers by strong fibrous network permits fabrication of PMC characterized by the following properties: high tensile strength, high stiffness, high fracture toughness, good abrasion resistance, good puncture resistance, good corrosion resistance, low cost. Reinforcing fibers may be arranged in different forms: unidirectional fibers, roving’s, veil mat: thin pile of randomly oriented and looped continuous fibers, chopped strands: thin pile of randomly oriented and looped short (3-4 inches) fibers, oven fabric. Properties of PMC’s are determined by: properties of the fibres, orientation of the fibers, concentration of the fibers and properties of matrix. Properties of
International Journal of Advanced Engineering Research and Studies PMC’s may be estimated by the rule of mixtures. PMC’s are used for manufacturing secondary load bearing aerospace structures, boat bodies, canoes, kayaks, automotive parts, radio controlled vehicles, sport goods (golf clubs, skis, tennis racquets, fishing rods), bullet-proof vests and other armor parts, brake end clutch linings. 2. MATERIALS & METHODS The general purpose polyester resin was procured from Hyderabad, India. It is an unsaturated resin having viscosity 400-500 cps (Brookfield viscometer) and specific gravity of 1220 kg/m3 at 250C. 2.1 Extraction & Preparation of Banyan Fiber Barks of banyan tree are collected from the VUDA park, Vijayawada. Barks are allowed to be dried for two days and with the help of blades the bark is sliced out into small short length fibers i.e, 20mm, 30mm, 40mm. The sliced out fibers are allowed to dry up for one week in order to prevent the effect of moisture completely. 2.1.1 Separation of Fibers as per weight percentages: The weight of the pure polymer is 15 gm. Since we are anticipating some increase in strength we want to know at what percentage of fiber has been increased, for that reason we separated fibers in terms of percentages that is 0.5%, 1%, 1.5%, 2%, 2.5%. Table of 15 samples showing the various weight percentages of different fiber lengths
Pure Polymer weight is 15gm. 2.2 Preparation of Polymer For use in molding, a polyester resin requires the addition of several ancillary products. These products are generally act as catalysts, accelerators. A manufacturer may supply the resin in its basic form or with any of the above additives already included. Resins can be formulated according to the moulders requirements, readily and simply for the addition of the catalyst prior to the molding. The rate of polymerization is too slow for practical purposes and therefore catalysts and accelerators are used to achieve the polymerization of the resin with in a practical time period. Catalysts are added to the resin system shortly before used to initiate the polymerization reaction. The catalyst does not take part in the chemical reaction but simply activates the process. An accelerator is added to the catalyzed resin to enable the reaction to proceed at workshop temperature and/or at a greater rate.
Schematic representation of Polyester resin (Uncured)
Schematic representation of polyester resin (Cured) IJAERS/Vol. I/ Issue II/January-March, 2012/256-258
E-ISSN2249–8974
The molecular chains5 of the polyester can be represented as follows, where B indicates the reactive sites in the molecule. With the addition of styrene ‘S’ , and in the presence of catalyst, the styrene cross links the polymer chains at each of the reactive sites to form a highly complex three dimensional network. The polyester resin is said to be cured. It is now a chemical resistant (and usually) hard solid. The cross linking or curing process is called ‘Polymerization’. It is a non reversible chemical reaction. The side –by –side nature of this cross linking of the molecular chains tends to means that polyester laminates suffer from brittleness when shock loads are applied. Great care is needed in the preparation of the resin mix prior to molding. It is also important to add the accelerator and catalyst6 in carefully measured amounts to control the polymerization reaction to give the best material properties. Too much catalyst will cause too rapid a gelation time, whereas too little catalyst will result in under cure. 2.2.1 Directions for Polyester hardener Polyester resin is catalysed with MEKP (methyl ethyl ketone peroxide) the ratio is approximately one Amount of Resin Hardener Required 28.35 gm 10 drops 46 gm 3.55 gm (7 CC) 92 gm 7.1 gm 184 gm 14.2 gm 368 gm 28.35 gm These amounts are easily measured in the ounce cup which is supplied with the resin, the above ratio should give a pot life of about 15-20 min. Time will vary from winter to summer since polyester hardens as it produces heat, the ratio of hardener to resin can be increased or decreased by 50 % to adjust for weather, thickness or your working preference. 2.3 Fabrication & Testing of Composites Various steps involved in making of composite are: Collection of fiber, separation of fibers as per length, separation of fibers as per weight percentages, preparation of mold as per ASTM D638-I, making of a composite and extraction of composite from the mold. 2.3.1 Preparation of mold as per ASTM D638-I
Specimen [ASTM D638 Type- I] This test method covers the determination of the tensile properties of unreinforced and reinforced plastics in the form of standard dumbbell-shaped test specimens when tested under defined conditions of pretreatment, temperature, humidity, and testing machine speed. This test method can be used for test materials of any thickness up to 14mm (0.55 inch). However, for testing specimens in the form of thin sheeting, including film less than 1.0 mm (0.04 inch) in thickness, Test methods D 882 is the preferred test method. In order to know tensile strength of any polymer composites, ASTM (American society for
International Journal of Advanced Engineering Research and Studies testing and materials) has suggested some dimensional codes i.e., ASTM D 638 series7. Shape of dimensional code was made on acrylic sheet by using a jig saw machine and it is attached to the glass plate. 2.3.2 Making of composites: Pattern made by acrylic sheet is attached on the glass sheet by using fevicol, in order to prevent the sticking of polymer to the acrylic sheet, stickered tape on the boundaries of the acrylic pattern. 2.3.3 Extraction of composite from the mold: In order to remove the composite from the mold, we heated the mold set up by using a candle. This heat will evaporate the fevicol attached between the acrylic and the glass plate thereby the composite is removed easily. 2.3.4 Testing of Composite using UTM: The mechanical properties of a material are directly related to the response of the material when it is subjected to mechanical stress. Since characteristic phenomena8 or behavior occur at discrete engineering stress and strain levels, the basic mechanical properties of a material are found by determining the stress and corresponding strains for various critical occurrences. A wealth of information about a material’s mechanical behavior can be determined by conducting a simple tensile test in which a cylindrical or flat specimen of uniform cross-section is pulled until it ruptures or fractures into separate pieces. The original cross sectional area and gauge length are measured prior to conducting the test and the applied load and gauge displacement are continuously measured throughout the test using computer-based data acquisition9. Based on the initial geometry from which numerous mechanical properties, such as yield strength and elastic modulus, can be determined. Universal testing machines, which can be hydraulic or screw based, are generally utilized to apply the test displacement/load in a continuously increasing (ramp) 3 RESULTS Table show the ultimate tensile strength of composite10 samples of different fiber lengths and different percentages of banyan fiber.
Pure Polymer: 33.87 Mpa 4 CONCLUSIONS There has been a growing interest in utilizing natural fibers as reinforcement in polymer composite for making cost effective construction materials in recent years. Economic and other related factors in many developing countries where natural fibers are abundant demand that scientists and engineers apply appropriate technology to utilize these natural fibers as effectively and economically as possible to produce good quality fiber reinforced polymer composites11 for home and other needs. Among the various natural fibers, banyan is of particular interest in that its composites have high impact strength besides having moderate tensile & flexural properties. IJAERS/Vol. I/ Issue II/January-March, 2012/256-258
E-ISSN2249–8974
As our work shows that ultimate tensile strength12 of composite specimen is 10-15% less than the pure polymer but the places where we give less importance to Ultimate tensile strength, banyan tree fiber reinforced composites has better applications like insulation boards, door panels, package trays, automobile interior, air craft interior, ceiling tiles etc. Since our work is in initial stages only there is a lot of scope for banyan tree fiber in future. 5 ACKNOWLEDGEMENTS One of the authors, T. Vijaya Kumar is thankful to Jyothi spectro analysis Balanagar, Hyderabad for utilizing the lab facilities to conduct tension test and to Dr .A.V. S. Jaya Annapurna, Asst. Prof, CSS Department KL University for necessary suggestions. REFERENCES 1.
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