bamboo fiber

International Journal of Metallurgical & Materials Science and Engineering (IJMMSE) ISSN 2278-2516 Vol. 3, Issue 4, Oct 2013, 15-22 © TJPRC Pvt. Ltd.

EVALUATION OF MECHANICAL PROPERTIES OF COCONUT COIR/BAMBOO FIBER REINFORCED POLYMER MATRIX COMPOSITES P. N. E. NAVEEN1 & R. V. PRASAD2 1

Department of Mechanical Engineering, Godavari Institute of Engineering and Technology, Rajahmundry, Andhra Pradesh, India 2

Department of Mechanical Engineering, MLR Institute of Technology & Management (MLRITM), Hyderabad, Andhra Pradesh, India

ABSTRACT Fiber-reinforced polymer composites have played a dominant role for a longtime in a variety of applications for their high specific strength and modulus. The fiber which serves as a reinforcement in reinforced plastics may be synthetic or natural. Past studies show that only synthetic fibers such as glass, carbon etc., have been used in fiber-reinforced plastics. Although glass and other synthetic fiber-reinforced plastics possess high specific strength, their fields of application are very limited because of their inherent higher cost of production. An attempt has been made to utilize the coir, as natural fiber abundantly available in India. Natural fibers are not only strong and lightweight but also relatively very cheap. The present work describes the difference between development and characterization of a new set of natural fiber based polyester composites consisting of coir, bamboo fiber as reinforcement and epoxy resin. Coir composites are developed and their mechanical properties are evaluated, at six different volume fractions and tests were carried out and the results were presented. Experimental results showed static properties of the composites are greatly influenced by the increasing percentage of reinforcement, and indicate coir can be used as potential reinforcing material for many structural and non-structural applications.

KEYWORDS: Natural Coconut Fibers, Bamboo Fiber, Polyester Matrix, Different Volume Fractions of Reinforcement, Mechanical Properties

INTRODUCTION The composite material has been used from centuries ago, and it all started with natural fibers. Natural fibers have become important items in the economy and in fact, they have turn out to be a significant source of jobs for developing countries. Natural fibers can be easily obtained in many tropical and available throughout the world. Today, these fibers are assessed as environmentally correct materials owing to their biodegradability and renewable characteristics. For example, natural fibers like sisal, jute, coir, oil palm fiber have all been proved to be good reinforcement in thermoset and thermoplastic matrices. Nowadays, the increasing interest in automotive, cosmetic and plastic lumber application has heightened the need of natural fibers reinforced composites in these regimes as it offers an economical and environmental advantage over traditional inorganic reinforcements [1]. Therefore, many industrial companies are looking for new composites material which has good and specific properties like mechanical and chemical characteristic. In searching for such new material, a study has been made where coconut fiber (also known as coir fiber) is compounded with composite material. Coir is the natural fiber of the coconut husk where it is a thick and coarse but durable fiber. It is relatively water-proof and has resistant to damage by salt water and microbial degradation.

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P. N. E. Naveen & R. V. Prasad

Cellwall

Lumen

Figure 1: Coconut Tree, Coconut and Fibers Outer Husk of the Coconut Figure 1 shows the outer husk of coconut fruit which can be used as a source of fiber and coir pitch.The example of application of coir fiber reinforced composites is in industrial automotive where it used to make seat cushions for Mercedes automobiles. Even though it has advantageous properties, the coir fiber composites still have some undesirable properties such as dimensional instability, flammability which not suitable for high temperature application and degradability with humidity, ultraviolet lights, acids and bases [2]. Therefore, a lot of efforts have been carried out to improve the performance of coir fiber reinforced composites. Recently there have been a lot of researches developed in the field of natural fiber reinforced composites [6]. The bamboo tree belongs to a group of woody perennial evergreen plants in the true grass familyPoaceae, subfamily Bambusoideae, tribe Bambuseae. It is one of the fastest growing woody plants in the world. This is perhaps due to their unique rhizome system and is dependent on local soil and climate conditions. They are of economic and high cultural significance in East Asia and South East Asia where they are used extensively in gardens as building material as well as food source. While wood has a hard centre and becomes weaker toward the outer part, bamboo is hard in its outer, while weak in its inner parts, this leads to a much more stable construction. The more stable fiber structures are most dense where you find the highest stress [13]. Accordingly, the adoption of bamboo fibre in composite application, especially in low strength areas will be most desirable.

Figure 2: Bamboo Culms and Sample

Evaluation of Mechanical Properties of Coconut Coir/Bamboo Fiber Reinforced Polymer Matrix Composites

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However, most of them are based on the study of the mechanical properties of composites reinforced with short fibers. This paper addresses the characterization and performance of natural fiber reinforced composite by analyzing the effect of fiber volume (%) on the composite mechanical properties. The composites were obtained by compounding polyester matrix and coir fibers in a batch mixer to obtain a randomly oriented discontinue form. The choose of polyester as a matrix is based on economic interest because it offers a very cheap resin, available with good mechanical properties and used in many applications such as transport, marine and sport.

MATERIALS AND METHODS The composite material was made of polyester matrix reinforced with coconut fibers. They were arranged in discontinuous randomly oriented configuration. Basically, coir fibers were obtained from coconut husk, which was abstracted from coconut fruit. After they were abstracted, the coir fibers will be dried at 80 oC using drying oven to minimize the moisture content in the fibers which can prolong their span life. In order to enhance the bonding compatibility between the polyester and fibers, the coir fibers need to go through the treatment process. This process consists of immersing the coir fibers into 5% Natrium Hydroxide (NaOH) solution for 24 hours to remove the unwanted layer of coconut coir fibers. After that, the fibers were washed abundantly with water to remove the NAOH before they dried again in furnace at 70 oC to 80oC for next 24 hours. The coir fibers were then soaked into the solution of 5% silane and 95% methanol for 4 hour and dried at 70 oC for next 24 hours curing time. After the drying process finished, the coconut fibers was inserted into the cutting machine to cut into smaller pieces. This form is called whickers which its length is less than about 10 mm. The advantage of whickers is that they can easily pour into the mixture of coconut fibers and polyester in ASTM D638 Type 1 mould (Tuttle 2004). The mechanical properties of coir fibers are shown in Table3. Table 1: Properties of Coir Fibers Property Density (g=cm3) Modulus (GPa) Tensile strength (MPa) Elongation to failure (%) Water absorption (%)

Coir 1.2 4-6 175 30 130-180

The usage of polyester resin as a matrix was chosen because it is the standard economic resin commonly preferred material in industry. In fact, it yields highly rigid products with a low heat resistance property [9] thus polyester resin was prepared by mixing polyester of density 1.28 g/cm3with hardener 3554B of density 1.05 g/cm3 at weight ratio 100: 1. The mechanical properties of polyester resins are given in table2. Table 2: Mechanical Properties of Polyester Resin [9] Mechanical Properties Density (g/cm3) Tensile Elongation at break (%) Tensile strength (MPa) Compressive Strength (MPa) Young’s modulus (GPa) Water absorption (%) 24h at 200C

Polyester Resin 1.2-1.5 2 40-90 90-250 2-4.5 130-180

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Figure 3: Comparison of Bamboo with Other Natural Fibers Extraction of Bamboo Fibre The collected bamboo fibres were extracted by chemico-mechanical process. The process involved the impregnation of sample with “white liquor’ and conversion of the softened sample into fibre by mechanical action, followed by thorough washing, screening and drying. The extracted fibres were separated, re-washed and dried in the forced-air circulation type oven. The fibres were subsequently weighed and percentage yield determined. The fibre systems were fluffed and separated into two tangle mass bulks, one for surface-treated fibre composite while the other for the ‘as natural’ fibre composite production. Surface Treatment of Bamboo Fibre The process adopted in this work was the silane treatment preceded by the sodium hydroxide treatment. Known weights of extracted bamboo fibreswere soaked in prepared known volume of 0.5 mol/litre of NaOH for 2 hours. The products were removed and washed with distilled water before air-drying. Subsequent processes included soaking the treated Bamboofibres in 2% phenlysilane solution for 24 hours. Subsequently, the product was removed, dried at 60 0C and stored in specimen bag ready for use. Production of Test Specimen The test specimen panels of 5-30% bamboo fibre content were produced by hand lay-up process. Curing was assisted by placing the composite in an oven operated at 110 0C. The mouldings were removed from the oven after 30 minutes and conditioned. Five (5) test samples each was cut from seven (7) stocks (5-30%) of the surface-treated bamboo reinforced composite and coir fiber reinforced composites. The example of the calculations is as follow: 

The total volume of the sample as in Figure 4 and 5 is calculated.

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5% of the total volume which is occupied by the fiber is determined and then the volume of the fibers is onverted to fiber weight using equation : Density Ρ= m/v Where, m is the mass of the fibers and v is the volume occupied by the fibers.

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Fibers are then mixed with polyester resin and they are mechanically stirred to produce Homogenous mixture.

Mechanical Testing Tensile test is the most common mechanical test for determining the mechanical properties of materials such as strength, ductility, toughness, elastic modulus, and strain hardening. There are 5samples for each fiber volume fraction and


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the average values obtained from those samples were determined. The sample used for tensile test was ASTM D638 Type 1 as shown in Figure 4. The tests consisted of applying10KN capacity operated at a crosshead speed of 5 mm/min.

Figure 4: Coir Fiber Reinforced Polyester Composite Tensile Test Specimen

Figure 5: Bamboo Fiber Reinforced Polyester Composite Tensile Test Specimen

RESULTS AND DISCUSSIONS The results of some mechanical strength properties and correlation of treated coir and bamboo fibre reinforced polyester composite panels are shown in Table 3: Comparison of Mechanical Properties of Treated Bamboo Fiber Reinforced Polyester Composites with Coir Fiber Reinforced Polyester Fiber (%) 5 10 15 20 25 30

Coir Bamboo Coir Bamboo Coir Bamboo Coir Bamboo Coir Bamboo Coir Bamboo

Tensile Strength(Mpa) 25.2 4.93 21.4 9.8 17 9.82 15.3 9.91 13.8 9.4 11.5 8.97

Figure 6: Effect of %Fiber on Tensile Strength of Coir and Bamboo Fiber Reinforced Polyester Composite

Failure Strain (%) 3.4 5.9 4.6 7.4 5.5 8.6 6.8 10.2 7.9 11.5 9.3 13.22

Youngs Modulus(Gpa) 633 171.6 461.4 148.2 318.8 125.6 209.1 95.6 110 63.6 40 25.1

Figure 7: Effect of %Fiber on Failure Strain of Coir and Bamboo Fiber Reinforced Polyester Composite

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Figure 8: Effect of %Fiber on Young’s Modulus of Coir and Bamboo Fiber Reinforced Polyester Composite

CONCLUSIONS The research was carried out to investigate the mechanical analysis of randomly oriented fibers reinforced polyester composites. The effect of fibers volume on mechanical properties of composite was studied. The results were found that the mechanical properties have a strong association with the volume fraction of the fiber. In general, both the composites show better results at 5% of the volume fraction of the fibers even though coir fiber shows better values than the Bamboo fiber. The tensile strength and Young’s Modulus were found to be decreased with incorporation of coir fibers which again points to the ineffective stress transfer between fibers and polyester resin. However the increase of coir fibers will make the composite tend to have low stiffness and ductility. The tensile strength of composite was found to be linearly proportional to the natural frequency.

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