SSRG International Journal of Civil Engineering – (ICEEMST’17) - Special Issue- March 2017

ISSN: 2348 – 8352 www.internationaljournalssrg.org Page 1

Study on Critical length of Fiber on Natural

Areca Sheath Reinforced Polymer matrix

Composites by Tensile and Flexural Testings

1. Parvatini Sri Naga Venkat

PG Student

3. Chennakesava R

Research Scholar

2. Chethan M.R

Research Scholar

4. Dr. G.S Gopala Krishna

Principal and Research Supervisor

Abstract: In the present work, The naturally

extracted Areca fibers are used as a reinforcement

and Epoxy L-12 is used as polymer matrix and

prepared by using Hand lay-up method. Each

specimen is cured for 24 hours and then test

specimens were cut according to ASTM standards

for Tensile and Flexural Testing. In present work,

Physical property of Natural Areca fiber is carried

by using “Interference at Air Wedge method” and

Fiber Density was calculated. The critical Length

of Areca fiber will be analyze by conducting

Tensile and Flexural testing for three different

fiber size specimens prepared with a band width of

2mm starting from 29 to 25mm. Finally, the

obtained results will be evaluated with Analytical

F.E.A Method. These Natural Areca fiber

reinforced polymer matrix composites can be used

in low- Strength structural and Non- Structural

Applications.

Keywords— Areca fibers, Tensile Test,

Flexural Test, Critical length, Interference at air

wedge,, Finite Element Analysis(F.E.A), Natural

Fiber Composites(NFC).

I. INTRODUCTION

India has a major existence of natural fibers such

as Areca, Jute, Sisal fiber, Pineapple fiber, coir

fiber Ramie and Banana. It has been concentrated

on the development of natural fiber composites

basically to investigate new value added

applications. These natural fiber composites are

widely suited as wood substitutes in the house

buildings as well as in other construction sectors

also. In recent days the development of NFC in

India is based up on two main strategy that are to

prevent the depletion of forest resources and

ensuring good economic returns for the growth in

cultivation of natural fibers.

After meeting the challenges of development of

composite materials in aerospace sector, it has

been concentrated sharply in domestic and

industrial applications. Composite Materials are

having light weight, High strength to weight ratio

and good stiffness properties which made them to

replace the conventional , materials such as

metals, woods, plastics. The Researchers globally

focused their attention on NFC with Areca, Sisal

fibers, Coir fibers, Pineapple fibers, Jute fibers.

The natural fibers are used to cut down the price of

raw materials.

In addition, Small aspect ratio, smaller dia, high

strength fibers having high flexibility and are more

easy to fabricate. The matrix is a continuous phase

which may be a polymer or a metal or a ceramic.

Polymers have less strength, metals have

intermediate strength, stiffness but high ductility

and ceramics have higher strength, stiffness but

are brittle in nature. The matrix maintain fibers in

the proper orientation and spacing and protecting

them from abrasion and the environment.

Continuous phase of polymer matrix provides a

stronger bond between fibers and the matrix. In

polymer matrix composites, matrix transmits loads

to the fiber reinforcement through shear loading at

the interface.

So, the final properties of the lamina such as

strength and modulus of elasticity will depends up

on the reinforcement only. Air traps also an

important role which decides the properties of

composite. As the length to diameter ratio

decreases the gap between the fiber to fiber

decreases which leads to decrease in air traps. So

short fiber reinforced composites provides higher

strength

II: EXPERIMENTAL PROCEDURE

II.I Elements and Fabrication of composites

Areca fibers are used as the reinforcement and

Epoxy resin is used as polymer matrix material in

this composite.

ii.i.i Extraction of Natural Areca Fibers

Natural Areca sheaths are collected in palm tree

farms shown in figure.1 from the fallen leaves as

shown in figure.2 which is called as raw Areca

leaves which are 1M to 1.5M long as shown in

figure.3. These raw leaves are soaked in water for

SSRG International Journal of Civil Engineering – (ICEEMST’17) - Special Issue- March 2017

ISSN: 2348 – 8352 www.internationaljournalssrg.org Page 2

7-10 days. After soaking, Natural Areca fibers

shown in figure.4 is extracted by separating the

fibrous content and the fiber in the sheath.

Extracted fibers are dried in room temperature for

one day and then chopped in to required size.

The properties of Natural Areca sheath are shown

in Table.I

S.No Name Content%

i Ligin 13-24%

ii Hemicellulose 35-64.8%

iii Ash 4.40%

iv Water 8-25%

Figure 1. Palm tree farms

Figure 2. Areca Fallen leaf

Figure 3. Raw Areca Leaves

ii.i.ii Polymer Matrix Epoxy resin

Epoxy resins when compared to polyester resins,

they are more costlier because of cost of precursor

used such as Epi Chloro Hydrin. Because of

complex polymer chain of the epoxy and the

potential degree of control of cross linking

process, it gives a improved matrix in terms of

ductility and strenght. The Epoxy used is here is

only added with 10% of hardener and it can cured

at room remperature easily in 24 hours or it can be

instantly cured at the time manufacturing process

and known as pre-peg and pre impregnated fiber.

Figure 4. Areca Fibers

By the reaction of Epichlorohydrin (C3H5CIO)

with bisphenol-A in an alkaline solution the epoxy

polymers are prepared, which absorbs the HCL

released during the condensation polymerisation

reaction. Every chain has molecular weight

between 3000 to 900 with an epoxide, grouping at

each end of the chain but none within the chain of

polymers.

ii.i.iii Hardener.

The Epoxy curing action is done by mixing a

substance or mixture called hardener. It is added in

1:10 ratio with Epoxy. Epxy and hardener used is

shown in picture.5

ii.i.iv Releasing agent

Poly vinyl carbon powder (cold) is added to water

and a thin layer is applied on inner sides of the

mould. It is dry at room temperature for one hour

then epoxy is applied above it.

ii.i.v Composition of Composite material

Composite material composition for preparation of

samples for tensile and flexural testing are

purchased from market of Bangalore, India and

details are shown in table.2

SSRG International Journal of Civil Engineering – (ICEEMST’17) - Special Issue- March 2017

ISSN: 2348 – 8352 www.internationaljournalssrg.org Page 3

Figure.5 Epoxy and Hardener.

Table No.2 : Composite material composition.

ii.ii Fabrication of composite material

The fabrication of the Areca reinforced polymer

matrix composite is prepared at room temperature

and cured. The required quantities of Resin and

Hardener were mixed in beaker thoroughly as

shown in the figure.6. The Mixture is transferred

in to the mould and it is tightened with the help of

C-Clamps.

Figure.6 Mixing of Epoxy and Hardener in

Beaker.

ii.ii.i Solution Preparation

The required amount of mixture of resin and

hardener were weighted in the mix 10:1 ratio in a

beaker and stirring is done properly within 10

minutes as to avoid sudden solidification of the

solution. This facilitates to avoid air entraps inside

the solution .

ii.ii.ii Mould preparation

The mould is prepared with Mild steel of size

320x320x4 mm. It contains of two parts, upper

part which is having flat surface and lower part

which have 4mm thickness. The both parts are

tightened with C-Clamps. The plates prepared

from the mould will contains final size of

270x270x4 mm.

ii.ii.iii Castings of samples

Initially the mould is cleaned with Ethanol. Then

mould is coated with release agent and it is dried

for half an hour The mixture prepared was

transferred to mould cavity and poured up on the

fiber with are randomly distributed. The mould is

closed and fixed with C-Clamps.

ii.ii.iv Curing of Castings

Curing is done at room temperature for

approximately 24 hours. As soon as the curing is

completed, mould was opened and specimen is

taken out carefully and mould is cleaned with

Ethanol finally.

ii.iii Material properties testing of Composite

Materials

ii.iii.i Physical Properties

The Density of Areca fiber is found out by using

Basic physical instrumental setup known as

“Interference at Air Wedge Method”[3]. When a

small diameter fiber is placed in between the two

optically planed glass plates and a wedge shaped

air film is formed between two glass plates. If a

parallel beam of Monochromatic is made to

incidence perpendicularly on the wedge, the beam

gets refracted the upper glass plate. The two

reflected rays from upper less plate and lower

portion or air film form two coherent source.

As the two portions in the reflected beam are

derived from the same incidence beam and have

different phase difference interference occurs. This

interference pattern when viewed through a

travelling microscope, It appears as equally spaced

Dark and Bright fringes parallel to the edge of the

wedge. Interference at air wedge method

illustrated in figure.7

ii.iii.ii Mechanical Properties

Tensile and flexural tests were carried out by using

UTM for samples of three varying fiber size of

S.N

o Material

Specificatio

ns

Mix-

ratio by

weight

1 Polymer

Resin Lapox L-12

210

Grams

2 Hardener K-16 21.0

Grams

SSRG International Journal of Civil Engineering – (ICEEMST’17) - Special Issue- March 2017

ISSN: 2348 – 8352 www.internationaljournalssrg.org Page 4

2mm band which are 29mm, 27mm, 25mm, Each

test have three samples for tensile test and flexural

test, so total nine samples were tested for

respective varying size of fiber specimens.

Figure.7 Interference at air Wedge Method

ii.iii.i..i Interference at air Wedge method

Fringe width is calculated from scale readings of

travelling microscope and diameter of fiber is

calculated by using below formula.

Where T = Thickness of Fiber

𝜆 = Wave Length of sodium light

β = Fringe width

L = Length of the air wedge

The values of Fiber diameter varies from 0.28 to

0.325 mm.

From this value Density of fiber can be

calculated by finding weight of a single fiber of

known length, by using basic formula of Density =

weight/ volume. The density values of a single

Areca fiber is given in the table given below.3

Table.3 Physical properties of the Areca fibers

ii.iii.ii.i Tensile Test

The Tensile test on three fiber length varying size

plates were performed on three specimens of each

size by using Universal Testing Machine under

controlled room temperature and at a speed of

2mm/min speed of elongation. Each specimen is

of 250x25x4mm according to ASTM D3039

standard. The Universal Testing Machine is

computerized and the stress vs strain curve can be

obtained from the computer, from which the

ultimate tensile strength is calculated. Also the

Ultimate tensile strength can be calculated from

load vs elongation curve obtained from the same

testing method. Tensile Testing method is shown

in figure.8

ii.iii.ii.ii Flexural Test

The Flexural test on three fiber length varying size

plates were performed on three specimens of each

size by using Universal Testing Machine under

controlled room temperature. Two fixtures as

shown in figure.9 at a span length of 45mm is

fixed and up

Figure.8 Tensile Test on specimens

on it specimen is placed where mid point of

specimen is coincided with mid point of two

fixtures, so the the specimen was in over hanging

position. Each specimen is of 65x13x4mm

according to ASTM D790 standard. The Universal

Testing Machine is computerized and the stress vs

strain curve can be obtained from the computer,

from which the ultimate tensile strength is

calculated. Also the Ultimate tensile strength can

be calculated from load vs elongation curve

obtained from the same testing method. Tensile

Testing method is shown in figure.9

Figure.9 Flexural Test

III RESULTS AND DISCUSSION

iii.i Tensile Test

The tensile strength is useful to define the material

elongation properties along with strength and

modulus of the fiber can be analyzed. The bonding

Dia in mm Length of

fiber in mm

Density of fiber

in g/cm3

0.11-0.15 29-25 1.1 – 1.25

SSRG International Journal of Civil Engineering – (ICEEMST’17) - Special Issue- March 2017

ISSN: 2348 – 8352 www.internationaljournalssrg.org Page 5

between the matrix and reinforcement is of much

important to get better tensile strength values.

The tensile stress results of three varying fiber

reinforcement sizes is given in the table.4

Table.4 Tensile Stress Experimental results

Length

of fiber

(in mm)

Specimen

Numbers

Average

Stress

value

(N/mm2)

Modulus of

Elasticity

(N/mm2)

29 Specimen

No.1 10.44 2072.966

27 Specimen

No.2 14.09 2925.084

25 Specimen

No.3 12.74 2746.353

According to above results, the specimen with

27mm fiber size have more stress and modulus

values and this results is validated by F.E.M

analysis by using ANSYS software.

The experimental and Analytical results is shown

in table.5

Length of fiber

(in mm)

Experimental

Results

(N/mm2)

F.E.A Results

(N/mm2)

27 14.09 14.8

The Von-mises stresses and Elongaion plot from

F.E.A analysis is shown in figure.11 and figure.12

The F.E.A analysis is also compared among three

specimens, where the maximum Von-mises stress

results got for 27mm specimen. This validates the

findings of the experimental results.

Figure.11 Von-Mises stress for 27mm specimen

Figure.12 Elongation for 27mm specimen

iii.ii Flexural Test

The flexural test is useful to define both tensile

and compressive strengths along cross-sectional

area of the test specimen.

The Flexural stress results of three varying fiber

reinforcement sizes is given in the table.4

Table.5 Flexural Stress Experimental results

Length of

fiber (in mm)

Specimen

Numbers

Average

Flexural Stress

value (N/mm2)

29 Specimen

No.1 36.075

27 Specimen

No.2 86.33

25 Specimen

No.3 40

According to above results, the specimen with

27mm fiber size have more flexural stress and

modulus values and this results is validated by

F.E.M analysis by using ANSYS software.

The experimental and Analytical results is shown

in table.6

Length of

fiber (in

mm)

Experimental

Results (N/mm2)

F.E.A

Results

(N/mm2)

27 86.33 88.455

The Von-mises stresses and Elongation plot from

F.E.A analysis is shown in figure.13 and figure.14

Figure.13 Von-Mises stress for 27mm specimen

The F.E.A analysis is also compared among three

specimens, where the maximum Von-mises stress

SSRG International Journal of Civil Engineering – (ICEEMST’17) - Special Issue- March 2017

ISSN: 2348 – 8352 www.internationaljournalssrg.org Page 6

results got for 27mm specimen. This validates the

findings of the experimental results

Figure.14 Elongation for 27mm specimen

IV. CONCULSION

The Areca fiber reinforced polymer matrix

composites showed higher tensile and flexural

stress and modulus values at 27mm fiber size

reinforcement specimens. Which indicates that

27mm can be considered as critical length at

which higher stress values exhibits. Based on the

studies carried out by experimental as well as

F.E.A methods, the values are near close to each

other, it concludes that the natural areca sheath

fiber reinforced polymer matrix composites are

best suitable for structural and non-structural

applications and the diameter of the fiber is found

to be between 0.11-0.15 mm.

V. ACKNOWLEDGMENT

I would like to thank Department of Mechanical

Engineering, Faculty of Engineering,Christ

University, Bangalore, Karnataka And Nagarjuna

college of Engineering and Technology,

Bengaluru, Karnataka.

And Thanks to Chethan M.R, Chennakesava R.,

Dr. G S Gopala Krishna for intense helping

towards every step of project work.

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