Experimental Testing of Polymer Reinforced with Coconut Coir Fiber Composites

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 4, Issue 12, December 2014)

453

Experimental Testing of Polymer Reinforced with Coconut

Coir Fiber

Composites

N. Anupama Sai Priya

1

, P. Veera Raju

2

, P. N. E. Naveen

3

1,2,3GIET, RJY-Affiliated to JNTU Kakinada, India

Abstract— Reinforced polymer composites have played an ascendant role in a variety of applications for their high meticulous strength and modulus the fiber may be synthetic or natural used to serves as reinforcement in reinforced composites. Glass and other synthetic fiber reinforced composites consists high meticulous strength but their fields of applications are restrained because of their high cost of production. Natural fibres are not only strong & light weight but mostly cheap and abundantly available material especially in Konaseema Coast. The present work describes the development and characterization of natural fiber reinforced polymer composites. The mechanical properties are evaluated at five different volume fractions with the help of UTM and results were tabulated. Experimental results showed Tensile, static and water absorption of composites are greatly influenced by incorporating the percentage of volume fraction of reinforcement and indicate coir can be used as reinforcing material for many Structural and Non-Structural applications.

Keywordscoconut coir, hand-layup technique, polyester, water absorption test

I. INTRODUCTION

Environmental awareness is growing day by day. Worldwide researchers triggered by this reason to implement and utilize materials which are eco friendly. When compared to synthetic fibres and manmade fibres natural fibres become best alternative and it is cheaper and more economic and environmental friendly composite material. In this experiment coconut coir fibre is the natural fibre component chemically treated with alkaline solution. Here chemically treated and untreated fibres were mixed separately with polyester matrix and by using hand lay –up technique these reinforced composite material is moulded in to dumbbell shape. Four specimens were prepared in different volume percentage of coir fibres in order to get more accurate results.

II. CHEMICAL MODIFICATION OF FIBER

This chemical treatment is used to improve the adhesion between the polymer matrix and surface of the fiber and the strength of the fiber. Water absorption capacity of the fibers will also be reduced and helps to increase the mechanical properties. Out of the available chemical treatments, here we are using alkali treatment.

A. Alkaline Treatment

Treatment with alkaline or mercerization is one of the most used chemical treatment for natural fibers. This treatment will remove some amount of lignin, oil and wax from the external layer of the fiber cell; it decomposes cellulose into small segments and exposes the short length crystallites. Adding of NAOH (Aqueous sodium hydroxide) to coconut fiber assist the ionization to alkoxide from hydroxyl group

Fiber + NaOH-OHFiber –Na-o+H2o

Thus process of alkaline directly effects the cellulosic fibre and the degree of polymerization and the pulling out the lignin and hem cellulosic compounds. This treatment has two effects on fibres.

1) Surface roughness is increased to result good mechanical properties

2) It effects fiber strength and stiffness of it.

B.Methods of Testing

All the mechanical testing are performed are based on ASTM (American standard Testing Methods).three tests are performed they are ASTM D638 (tensile test), ASTM D790 (Impact Test) and ASTM D256 (Flexural Test).

C. Tensile Testing

Tensile test is used to measure the tensile strength of a material. It is the measurement of a material up to which extent it can bare the loads. It is the ability to resist the loads without failure. It can be determined by using stress strain diagram. According to (D638) dumbbell shape (Type I) specimen is needed for reinforced composite testing. Detail dimension for this are shown in the Table-1 The testing was done at standard lab temperature of 250 C± 2°C and fifty percent relative humidity.UTM was used at cross head at required speeds. Figure -1 shows the UTM used for tensile testing.

When tensile test was going on the material the specimen elongates and it increases the resistance power along the load cell. The load (P) is noted until the rupture of the work piece takes place. The computerized UTM calculates the tensile, yield and elongation properties at break point.

Tensile strength = Load (P)/Area(A)

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Table-1

Type I in ASTM D638 Dumbbell Shaped Specimen Dimensions

Dimensions

Value,

mm(in)

Thickness (T) <7mm (0.28in) 1.00 ± 0.4

(0.13 ± 0.02)

Width of narrow selection(W) 13 (0.5)

Length of narrow selection(L) 57 (2.25)

Width overall (WO) 19 (0.75)

Length overall ( LO) 165 (6.5)

Gauge length (G) 50 (2.00)

Distance between grips (D) 115 (4.5)

Radius of fillet (R) 76 (3.00)

Figure-1 UTM (Instron 5567) for Tensile Testing

D. Fibre reinforced composites

Examples of composite materials naturally available are wood, bamboo and bone. Wood and bamboo consist cellulose and lignin where as bone consists of collagen and apatite. In natural fibres the content of cellulose is depends upon the type of fibre. In some natural fibres it may be in the range of 60 wt% to 80 wt% and lignin is from 5 wt% to 20 wt%. Table 2 Shows the properties of cc fibres.

Table -2 Properties of Coir Fibres

Property Coir

Density (g=cm3) 1.2

Modulus (Giga Pascal) 4-6

Tensile strength (Mega pascal) 175

Elongation to failure (%) 30

Water absorption (%) 130-180

III. OPEN MOULDING:HAND LAY-UP TECHNIQUE A. Introduction

Open Molding, also known as contact molding, open laminating, and wet lay-up, is the method used longest in the polymer-matrix composites industry to make thermo set composite products, and it is still the selected production process for a wide range of composite products. It is a basic process that provides many of the advantages of composites processing, using relatively basic materials technology and processing methods. The molding method involves placing reinforcements and liquid resin onto the surface of an open mold (which may or may not be pre-coated with gel coat), or onto other substrates, as, for example, when making a one-off sandwich construction, when making on-site repairs by applying a reinforcing vacuum-formed acrylic, corrosion-resistant lining on steel, or when making on-site repairs of tanks and pipes. The hand lay-up version involves applying the reinforcements and the resin by hand, while the spray-up version uses tailored spray equipment to deposit both reinforcements and resin on the mold or an alternative substrate.

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The hand lay-up process involves low investment costs and little prior working knowledge of the process, while spray-up involves some investment in tailored spray-up machines and spray guns. Well-trained operators and dedicated facilities are required to produce components and products having high quality.

A. Process Characteristics

Open molding offers a number of process and product advantages over other high-volume, complex application methods and is therefore used for a number of specialized products.

Process advantages include:

 Freedom of design

 Easy to change design

 Low mold and/or tooling costs

 Low start-up costs

 Low to medium capital costs

 Regarded as a simple process

 Tailored properties possible

 High-strength large parts possible

 Large-sized parts possible

 On-site production (one-off) possible

Disadvantages associated with the open molding process include:

 Low to medium number of parts/year

 Long cycle times per molding

 Labor intensive

 Not the cleanest application process

 Only one surface has aesthetic appearance

 Operator-skill dependent

 Sharp corners and edges limited

 Long reworking time per molding

 Limited amount of filler to modify properties

IV. PROCESS DESCRIPTION

The hand lay-up process is illustrated in Fig 2. Before starting the actual laminating process, the mold surface has to be clean and prepared with a suitable mold-release agent, which must be properly cured before the catalyzed gel coat is applied. The catalyzed gel coat typically is applied after curing. Gel coat is a tailored pigmented or non pigmented resin that typically is applied as the first 400 to 700 μm outer layer. It not only provides the surface quality, but it also functions as a protective layer against weathering and other exposure, protecting the final underlying reinforced laminate from direct environmental attack and consequent possible unwanted degradation of laminate properties. The recommended type and amount of organic peroxide (typically 1.5–2 wt% of good methyl ethyl ketone peroxide) must be added to the preaccelerated gel coat before use; however, it often is preaccelerated by the supplier.

FIGURE -2 Hand lay-up Method

In the case of pure hand lay-up, the gel coat is also applied by hand, using a suitable soft brush. Curing time is typically a few hours at ambient temperature, after which application of resin and reinforcements can start. A suitable type and amount of a given curing system must be added to the resin before starting the actual laminating operation. This depends on the type of resin used, so it is recommended that the supplier be consulted for specifics.

A. Modelling and manufacturing of die

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FIGURE 3 ASTM D638 Type 1 mould

B. Material

Matrix: Polyester Resin Hardener: Catalyst Accelerator: cobalt

Specimen size: As per ASTM D638 Type 1 mould

FIGURE 3 Materials Required

V. EXPERIMENTAL PROCEDURE

Basically two important tasks of this experiment were carried out to reach the main objective of the study. Task one is to preparation of composite material by mixing the coconut coir and polyester. After that the experiment was continued be conducting the tensile test to find mechanical characteristics of composite

A. Material

In this experiment the composite product is made of coconut coir fiber reinforced with polyester matrix both were arranged in randomly discontinuous oriented configuration. In this coconut coir fiber is extracted from coconut fruit. When coming to the experiment first the coir fiber is dried at 70o C-80o C using oven.

To avoid factor of degradation it is necessary for the coir fibers to go through the treatment process. In this process the coir fiber is soaked in NaOH solution for min 24 Hours later it is abundantly washed with plain water to remove NaOH and the top layer of the coir fiber.

After this we have to make the coir dry by using furnace between 70o C-80o C for next 24 Hours. next 24 hours curing time in this time The coir fibres were then soaked into 5% of silane and 95% of methanol solution for 4 hour and dried at 70°C.after this drying process the coir was inserted into the cutting machine to cut it to small pieces. These small pieces were called whickers whose length is < 10 mm.these whickers can easily pour into the mixture of polyester and coconut fibres in ASTM D638 Type 1 mould (Turtle 2004). The physical properties of coir fibres are shown in Table 3

TABLE 3

Physical properties of coir fibres

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TABLE 4

Mechanical properties of polyester resin

B. preparation of Mould

Here the mould used for coconut fibres composite for tensile testing purpose is made of mild steel which followed the ASTM D638 Type 1 standard as shown as in Figure 4

FIGURE. 4 ASTM D638 Type 1

Mechanical properties Polyester

Resin

Density (g/cm3) 1.2-1.5

Tensile Elongation at break (%) 2

Tensile strength (MPa) 40-90

Compressive Strength (MPa) 90-250

Young’s modulus (GPa) 2-4.5

Water absorption (%) 24h at

200C

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C. Composites Preparation

Composites having different fibres content were prepared by varying the fibres volume from 5% to 15%. When started preparation of composite first process was to introducing a release agent it was used to clean and dry the mould before the polyester can be laid up on the mould. The polyester was then mixed uniformly with the coconut fibres by using a special brush in the mixed container. The mixture was poured carefully into the moulds and flattened appropriately by using the roller before being dried for 24 hours. After the composites were fully dried, they were separated off from the moulds.FIGURE.5 Dumbbell shaped composite material

FIGURE.5 Dumbbell shaped composite material

A. Mechanical testing

Tensile testing is the most common mechanical testing for determining the physical properties of materials such as strength, ductility, toughness, elastic modulus, and strain hardening. The tests consist of applying a constant strain on the fibres and measure the load. Universal Testing Machine was used with strain speed of 10 mm/min. The distance between clips was defined of 115 mm. Four specimens were prepared in the study for each percentage of coir fibres in order to get more accurate results.

FIGURE.6 Dumbbell shaped specimen under testing

B. Mechanical properties

The influence of fibers content on mechanical properties of coir fibers reinforced composites was investigated. Table 7.1 shows the result of mechanical properties of coir fibers reinforced composites with fibers volume changing from 5 to 15%.

C. Mechanical properties TABLE 5

Mechanical properties of composites with different coir fibres volume

Graph 1. Failure strain of composite

FIGURE 2 Tensile strength

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Water absorption Test:

Untreated: Water absorption % vs % of the Fibre TABLE 6

Shows the untreated cc composite tensile strength values at different time periods

0

(Hours) 24(Hours) 72(Hours) 120(Hours)

5% 4 2 3 4

7.5 9 9.2 9.5 9.8

10 12 11 12.3 13

12.5 14 13 14.5 17

15 16 15 17 19

Graph 4 Showing the result of water absorption test of untreated coir

TABLE 7

Chemically treated: Water absorption % vs % of the Fiber

0(Hours) 24(Hours) 72(Hours) 120(Hours)

5% 8 9 8 9

7.5 9 9 9.5 10

10 11 11 11.5 11

12.5 13 13.5 14 14

15 15 16 17.5 18

Graph 5 Shows the Water absorption % vs % of the Fiber

In The fiber treatment, the values of tensile strength decreased as the amount of fiber increased. The chemically treated coconut coir composites presented higher tensile strength than the fibers which were untreated. This enhancement is associated to the inequity of the hydropolic character of the fibers which were treated related to reduction of polar components (-OH) and could be seen from water absorption test results. As the consequence of surface modifications, water absorption test values of chemically treated coconut coir samples were higher (9%) than results obtained to untreated PP-Fiber (4%) due to reduction of –OH present on the fiber surface.Thus chemical treatment of coir by using Alkali is environmental friendly processes and produced composite materials are suitable to be applied in marine applications.

VI. CONCLUSION

The research was carried out to find the static and water absorption behavior of randomly oriented coir fibers mixed with reinforced polyester composites. The influence volume fraction of coir fibers on mechanical properties of composites was studied. The static and water absorption properties are highly dependent on volume percentage of fibers. In general, the composites having volume of 5% coir fiber showed notable result when compared to high fiber loading composites due to the effect of material stiffness. natural frequency of composites was found to be proportional to The tensile strength.The chemically treated fibers having more tensile strength when compared to untreated coconut coir fibers. When the fibers tested in water at different time periods there is a slight change in their tensile properties. The difference is very less. Due to this reason we can use composites in different applications like turbine blades, marine application.

A. Recommendation For Further Research

There is a very wide scope do researches in this area

 We can test other properties like chemical properties ,shear properties of coconut coir composites

 In place of short coir fibers we can use long fibers to test the properties

 Instead of plain water by using salt water we can test the coir fibers properties

REFERENCES

[1] Jartiz, A.E., 1965, ―Design,‖ pp. 18.

[2] Kelly, A., 1967, Sci. American, 217, (B), pp. 161.

[3] Berghezan, A., 1966, ―Non-ferrous Materials,‖ Nucleus, 8: pp. 5–

11. 0 5 10 15 20

5 7.5 10 12.5 15

Wate r ab sor p tion %

Volume Fractions of the Coir

0 hr

24 hr

72 hr

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[4] Van Suchtelen., 1972, "Product properties: a new application of

composite materials," Philips Res. Reports, Vol. 27, pp. 28.

[5] Agarwal, B.D. and Broutman, L.J., 1980, ―Analysis and

performance of fiber composites,‖ John Wiley & Sons, New York, pp.3-12.

[6] Outwater J.O., ―The Mechanics of Plastics Reinforcement

Tension,‖ Mod. Plast: March- 1956.

[7] Wetter, R., 1970, ―Kunststoffe in der Luft-und Raumfahrt,‖

Kunststoffe, 60, Heft-10.

[8] Schmidt, K. A. F., 1967, Verstarkungsfasern in

Glasfaserverstärkte Kunstoffe, Ed. P. H. Selden, Springer-Verlag, Berlin, pp.159-221.

[9] Hinrichsen, G., Khan, M.A. and Mohanty, A.K., 2000,

―Composites‖: Part A, Elsevier Science Ltd, 31:pp.143–150.

[10] Joseph, P.V., Kuruvilla J, Thomas S., 1999, ―Composites Science

Figure

Figure-1 UTM (Instron 5567) for Tensile Testing
Figure-1 UTM (Instron 5567) for Tensile Testing p.2
Table-1  Table -2
Table-1 Table -2 p.2
FIGURE -2  Hand lay-up Method

FIGURE -2

Hand lay-up Method p.3
TABLE 3  Physical properties of coir fibres

TABLE 3

Physical properties of coir fibres p.4
FIGURE 3 ASTM D638 Type 1 mould

FIGURE 3

ASTM D638 Type 1 mould p.4
TABLE 4   Mechanical properties of polyester resin

TABLE 4

Mechanical properties of polyester resin p.5
FIGURE. 4 ASTM D638 Type 1
FIGURE. 4 ASTM D638 Type 1 p.5
TABLE 5 Mechanical properties of composites with different coir fibres

TABLE 5

Mechanical properties of composites with different coir fibres p.6
FIGURE.6 Dumbbell shaped specimen under testing
FIGURE.6 Dumbbell shaped specimen under testing p.6
FIGURE.5 Dumbbell shaped composite material
FIGURE.5 Dumbbell shaped composite material p.6
TABLE 6  Shows the untreated cc composite tensile strength values at

TABLE 6

Shows the untreated cc composite tensile strength values at p.7
TABLE 7   Water absorption % vs % of the Fiber

TABLE 7

Water absorption % vs % of the Fiber p.7

References