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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