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Study of Mechanical Properties of Coconut Shell Powder and Tamarind

Shell Powder Reinforced with Epoxy Composites
To cite this article: T M Somashekhar et al 2018 IOP Conf. Ser.: Mater. Sci. Eng. 376 012105

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IConMMEE 2018 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 376 (2018) 012105 doi:10.1088/1757-899X/376/1/012105
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Study of Mechanical Properties of Coconut Shell Powder and

Tamarind Shell Powder Reinforced with Epoxy Composites

Somashekhar T M1 Premkumar Naik2 VighneshaNayak3 Mallikappa 4 Rahul S5

1,3,5Department of Mechanical Engineering, Mangalore Institute of Technology &
Engineering, Moodbidri, D.K, Karnataka, India - 574225
2Department of Mechanical Engineering, AMC Engineering College, Bangalore
4 Department of Mechanical Engineering, NMAMIT Nitte D.K, Karnataka, India

Corresponding author: *somashekhar@mite.ac.in

Abstract. Coconut shell is non-food part which is one of the hard agro wastes. Coconut shell is
high potential material due to its high strength and modulus properties. Coconut shell powder
exhibits admirable properties compared to other materials such as low cost, renewable, high
specific strength to weight ratio, low density less abrasion to machine and environmental
friendly. Mixing coconut shell powder with epoxy resin enhances its properties and creates a
wide range of applications. Tamarind shell is also a non-food part which is an agro waste. After
the tamarind fruit is extracted these shells are disposed as waste. As these shells are hard they
provide better strength when used in composite materials as an additive. The components are
made by mixing coconut shell powder, tamarind shell powder and epoxy resin at definite ratios
and is tested for mechanical properties. The present study deals with preparation and
experimentally testing the mechanical properties of Coconut Shell Powder and Tamarind shell
powder reinforced epoxy resin composites. 3 different percentages of coconut shell powder and
epoxy resins are made to form composite material and then results are analysed for those 3
composite materials. From the results it has been found that tamarind shell powder with
coconut shell powder, increases the tensile properties by around 50%. The best result and
increase in mechanical properties is obtained when the composition of the material is 50% of
Coconut shell powder and 5% of Tamarind shell powder along with 45% of epoxy resin.

1. Introduction
In the latest years, composites fulfil optimal requirement criteria for several designers’ materials.In the
last 50 years, there have been major developments in the design and fabrication of light-weight, high
strength materials, primarily due to the increase of polymer composite materials1. Several researchers
have aimed at their work towards defining abundant combinations of biodegradable matrix/natural
fillers in order to promote new classes of biodegradable composites with enhanced mechanical
properties, as well as to attain products with lower cost. Among several investigated natural fibers in
this area, different fillers have the significant importance[1].The Natural Fillers (NF) reinforced
materials offer several environmental advantages, such as decrease dependence on non-renewable
material sources, lower pollution and green house emission. Natural lignocelluloses fillers (flax, jute,
hemp, etc.) represent an environmentally friendly alternative to conventional reinforcing fibers (glass,
carbon). The Advantages of natural fillers over traditional ones are their low cost, high toughness,
corrosion resistance, low density, good specific strength properties and reduced tool wear2. However,
there are several disadvantages in natural fillers, like low tensile strength, low melting point, not
suitable for high temperature application, poor surface adhesion to hydrophobic polymers, non-
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IOP Conf. Series: Materials Science and Engineering 376 (2018) 012105 doi:10.1088/1757-899X/376/1/012105
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uniform filler sizes, degradation by moisture. Therefore, chemical treatments are done so as to modify
the fiber surface properties[2].
A composite is a structural material that consists of two or more constituents that are combined at a
macroscopic level and are not soluble in each other. Composites have two constituents, a matrix phase
and a dispersion phase. One constituent is called the reinforcing phase and the one in which it is
embedded is called the matrix.In a composite, the fiber, as well as the matrix, retain their physical and
chemical identities, but still provide a combination of properties that cannot be achieved with either of
the constituents alone. In general, the fibers play the role of load bearer. The matrix, while keeping the
fibers in the desired location and orientation, act as a load transfer agent and protects the fibers from
external conditions such as chemicals, heat and moisture.Man-made fibers using glass, carbon, boron
etc. are being used as reinforcing materials in the fiber reinforced plastics (FRP), which have been
widely accepted as materials for structural and non-structural applications. The main reason for the
interest in FRP is due to their specific modulus, high stiffness and strength to weight ratio compared to
other conventional materials. However, these materials are prohibitively expensive in their use for
other general purpose and applications. Nowadays-natural fibers like banana, cotton, coir, sisal jute has
attracted the attention of scientists and technologists for applications in packaging, low-cost housing
and other structures. It has been found that these natural fiber composites possess better electrical
resistance, good thermal and acoustic insulating properties and high resistance to fracture[3,4,5].
Advanced composite materials with anisotropic properties created a new need for new test specimens
and test techniques. New test was required to evaluate reinforcing fibers, characterize matrix materials
and mechanical properties. The literature review on mechanical tests that have been developed to
define the mechanical properties of these engineered structural materials.According to Alok Singh et
al.[1] bio composite material was tested for dimensional stability, it exhibited very low water
absorption rates of less than 3 % and low thickness swelling of less than 1 %. These results have
shown that plant-based fibers may be used as reinforcement in a composite system to improve the
properties and performance of polymer matrix resins.Hayder Abbas Sallal [6], says that tensile
strength has increased with increasing weight fraction of (coconut shell powder) filler particles and
reached their maximum value at (6 % by wt). Furthermore, the increasing weight fraction revealed
decreasing properties of the prepared system. Also results had shown that compression strength and
impact energy increased with increasing weight fraction of (coconut shell powder) up to 6%wt. J.
OlumuyiwaAgunsoye, et al.[7] says,as the percentage of coconut shell powder increases, there was a
corresponding decrease in porosity. This property makes the composite suitable for the application in
the interior part of a motor car where materials with good hydrophobic characteristic are required.
According to Srinivas K. R. [8] et al., test for different mechanical properties were performed with
different percentage of tamarind shell powder and epoxy. In this experiment better tensile strength was
obtained when the composition was 80% of tamarind shell power and 20% of epoxy. From the
literature review it is found that combination of coconut shell powder and tamarind shell powder along
epoxy resin composites are scanty. Hence attempt been made to study the preparation and
experimentally testing the mechanical properties of Coconut Shell Powder and Tamarind shell powder
reinforced epoxy resin composites.

2. Material Preparation and Methadology

The coconut shell was dried in open air and grinded into powder using a pulverizing machine, the
powder was sieved in accordance with BS 1377:1990 standard. The chemical analysis of the coconut
shell was done with Absorption Spectrometer (AAS)-Peckinhelma 2006 model. The particle size used
was 300 µm. The pelletized polyethylene waste was sun-dried and shredded in a plastic crusher
machine. The coconut shell powder and the grinded pelletized (polyethylene) were blended together
using a two-roll rheomixer at 50˚C and a rotor speed of 60 rpm. The percentage of the filler in the
matrix was varied from 5% to 25% to produce five different compositions. Compression of the
composites was carried out with a hydraulic pressing machine for 7 minutes under controlled pressure

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IOP Conf. Series: Materials Science and Engineering 376 (2018) 012105 doi:10.1088/1757-899X/376/1/012105
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(30 tons) at 150˚C. Each of the samples was cooled to room temperature under sustained pressure
before it was removed from the press.
A hydraulic hot press is used to prepare the boards. The working principle of this press is, the material
from which board is to be prepared is compressed at an appropriate temperature and pressure. This set
up is kept for the known duration of time.The mould is placed in hydraulic press, which is maintained
at 140˚C, and then a pressure of 2 MPa is applied. The set-up is maintained undisturbed about 15-20
minutes. Later, the mould is taken out and allowed to cool for half-an-hour and remove the composite
board from the mould.

2.1 Different Types of Composite Plates

For preparation of A Composite plate, 30% of coconut shell powder and 70% of Epoxy resin are
uniformly mixed and used for preparation of boards. For preparation of B Composite plate, 40% of
coconut shell powder and 60% of Epoxy resin are uniformly mixed and used for preparation of boards.
For preparation of C Composite plate, 50% of coconut shell powder and 50% of Epoxy resin are
uniformly mixed and used for preparation of boards.For preparation of D Composite plate, 30% of
coconut shell powder and 15% of Tamarind shell powder along with 55% of Epoxy resin are
uniformly mixed and used for preparation of boards. For preparation of E Composite plate, 40% of
coconut shell powder and 10% of Tamarind shell powder along with 50% of Epoxy resin are
uniformly mixed and used for preparation of boards. For preparation of F Composite plate, 50% of
coconut shell powder and 5% of Tamarind shell powder along with 45% of Epoxy resin are uniformly
mixed and used for preparation of boards.

Table 1 Composite plates composition

Plate Name CS Powder in % TS Powder in % Epoxy resin in %
A 30 0 70
B 40 0 60
C 50 0 50
D 30 15 55
E 40 10 50
F 50 5 45

2.2 Tensile Test

Tensile strength of a material is the ability of the material to withstand tensile forces applied either
sides of the specimen. The test is used to determine the tensile strength and young’s modulus of the
material.
For this test Universal Testing Machine (UTM) is used. Using this machine with suitable jigs, almost
all mechanical tests are performed by this machine to determine the material properties. Figure 1
shows the typical UTM in working.
According to ASTM standards, the composite specimen was prepared for tensile testing to determine
the material properties. Each test specimen of 100 mm gauge length, 15 mm wide and thickness 6mm
were prepared as shown in figure 2. For this test UTM of capacity 100kN was used.All the required
dimensions of the specimen are entered into the computer along with the maximum load and
displacements are assumed and entered. After the failure of the specimen, the computer shows the
Load Displacement curve. From these obtained curves Stress, Strain and Young’s modulus were
evaluated.

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IOP Conf. Series: Materials Science and Engineering 376 (2018) 012105 doi:10.1088/1757-899X/376/1/012105
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The specimen prepared as per the standard is placed in the UTM with the arrangements of the jigs, as
the setup is clear, a constant state of loading is applied on the either sides of the specimens which are
equal and opposite in direction. The arrangement of the UTM with the specimen is shown in the figure
2.

Figure 1 Universal Testing Machine Figure 2 Universal Testing Machine - Tensile test

2.3 Flexural Strength

Flexural strength is the ability of the material to withstand bending forces applied perpendicular to its
longitudinal axis. The stresses induced due to the flexural load are a combination of compressive and
tensile stresses. The test is used to determine the flexural strength and stiffness.
The 3- point bending test provides values for the modulus of elasticity in bending, flexural stress,
flexural strain and the flexural stress-strain response of the material. The main advantage of a three-
point bending test is the ease of the specimen preparation and testing. However, this method has also
some disadvantages: the results of the testing method are sensitive to specimen and loading geometry
and strain rate. The arrangement for three-point bending test with bending fixtures is as shown in
figure 3.According to ASTM standard the composite specimens were prepared for bending test. Each
test specimen of 50-mm width, length 210 mm and thickness 6 mm as shown in figure 3 were
prepared. The span (center to center distance between roller supports) for each specimen is 160 mm.
the specimen is loaded at the center of the span through a loading cell. The test is carried until the
specimen completely fails.

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IOP Conf. Series: Materials Science and Engineering 376 (2018) 012105 doi:10.1088/1757-899X/376/1/012105
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Figure 3 Universal Testing Machine - Bending test

3. Results and Discussions

Composites are prepared with above specified composition and size and tested in UTM to get tensile
and flexural strength of material. Seven composites plates are prepared with different composition of
coconut shell powder, tamarind shell powder and epoxy resins. Before testing in UTM, water
absorption and hardness test are conducted.

3.1Water Absorption Test

Studies had revealed that mechanical properties such as toughness and resistance will fall after
exposure the specimen for moisture, or after absorption of specific quantity of water and the reason for
this, is that the moisture has a role in breaking the interface between the matrix material and the
reinforced material and by reducing the adhesion between the matrix material and the reinforced
material, or the reinforced material may absorb greater amounts of the water, causing swelling of the
matrix material and therefore separation in the matrix material will be expected and the detoration of
the interface in the composite material will happen and this leads to decreasing in transfer of stress to
the filler material and thus lead to decrease in toughness and resistance will be decreased. By
immersion of the specimen in water, the water absorption (change in mass) can be calculated
according to equation.
𝑚𝑎 − 𝑚𝑏
𝑊𝑎𝑡𝑒𝑟 𝑎𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 (%) = × 100
𝑚𝑏
Where mb = mass of specimen before immersion (g).
ma = mass of specimen after immersion (g).
The tests were carried out for 15 days and weight of the specimens were noted on the daily basis. The
specimen was cut into 40x40 mm and inserted in a beaker of water. 2 beakers were used, one filled
with distilled water and other with regular tap water. Long term water immersion method was used to
determine the absorption behaviour of composites. The conditioned composite sample was placed in a
beaker with water at 23±1º. At the end of 24 hours one of the sample is removed from the water at a
time, all surface water wiped off with a dry cloth and weighed immediately and then replaced in the
water and this procedure was repeated at every 24 hours till 15 days and the data was recorded. The
percentage increase in weight was calculated by above equation. Table 1 shows the experimental
results of water absorption test. From the calculated percentage of water absorption, it is clear that the
maximum percentage of water absorbed is 6.4%. Hence it creates a wide range of applications
regardless of the problem of water absorption.

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IOP Conf. Series: Materials Science and Engineering 376 (2018) 012105 doi:10.1088/1757-899X/376/1/012105
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Table 2 Water absorption test results

Water absorption (%)
Specimen
Tap Water Distilled Water
Component A 5.40 2.80
Component B 6.40 3.17
Component C 2.02 4.19
Component D 5.23 4.71
Component E 5.14 4.11
Component F 4.48 5.00

3.2 Hardness Test

A standard specimen is placed on the surface of the Rockwell Hardness tester. A minor load is applied
and the gauge is set to zero. The major load is applied by tripping a lever. After 15 seconds the major
load is removed. The specimen is allowed to recover for 15 seconds and then the hardness is read off
the dial with the minor load still applied. The standard specimen for ASTM D785 has dimensions of
20mm by 20mm. Figure 4 shows the variation of Rockwell hardness number for different composition
of composite material. From the above result it can be concluded that by the addition of required
amount of tamarind shell powder the surface hardness can be increased. Hence by experimenting with
addition of suitable percentage of tamarind shell powder we can obtain a better result.
Rockwell Hardness Number
60
Rockwell Hardness Number

50

40

30

20

10

0
A B C D E F
Composition

Figure 4 Variation of Rockwell Hardness Number w.r.t. Composition

3.3 Tensile test

Different composites are tested under UTM for tensile test and results are obtained. Load vs deflection
curve are obtained from UTM and then tensile strength is calculated. From the experimental data it is
clear that by the suitable addition of tamarind shell powder with coconut shell powder, increases the
tensile properties by around 50%.The best result and increase in mechanical properties is obtained
when the composition of the material is 50% of Coconut shell powder and 5% of Tamarind shell
powder along with 45% of epoxy resin. Figure 5 shows the effect of ultimate tensile strength for
different composite plates. In the future there is scope for further researches in order to increase tensile
as well as flexural test at a higher rate. With a proper mixing ratio and by varying the grain size a
composite with better properties can be prepared.Figure 6 shows the sample data of load-deflection
curve for F composite plate.

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IOP Conf. Series: Materials Science and Engineering 376 (2018) 012105 doi:10.1088/1757-899X/376/1/012105
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35
Ultimate Tensile Strength
UTS (N/mm2) and % of Elongation (%)
30 Percentage of Elongation

25

20

15

10

0
B C D E F
Composition
Figure 5 Variation of Ultimate Tensile Strength w.r.t. Composition

Figure 6 Load-Deflection curve for F composite plate

3.4 Bending Test

Figure 7 shows the effect of flexural strength for a different composite plates. From the results it can
be seen that as the percentage of coconut shell powder percentage increases in composites flextural
strength also increase. This is because better hardness for the coconut shell powder. Also from the
result it can be seen that 5% of tamarind shell powder will have highest flexural strength compared to
all other composites. This is because tamarind shell powder will improve the grain distribution in the
composites hence it will have higher strength when compared to all other composites. Flexural test
shows significant increase in its properties. But overall improvement in the mechanical properties can
be clearly observed.
The best result and increase in mechanical properties is obtained when the composition of the
materials is 50% of Coconut shell powder and 5% of Tamarind shell powder along with 45% of epoxy
resin.

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IOP Conf. Series: Materials Science and Engineering 376 (2018) 012105 doi:10.1088/1757-899X/376/1/012105
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120

100
Flextural Strength (MPa)

80

60

40

20 Flextural Strength

0
A B C D E F
Composition
Figure 7 Variation of Flexural Strength w.r.t. Composition

4. Conclusion
The use of Natural fiber polymer composites filled with natural-organic fillers, in alternate of mineral
inorganic fillers. The utilization of coconut shell powder in various applications has opened up new
avenues for both academicians as well as industries to design a sustainable module for future use of
coconut shell fibers. Coconut shell fibers have been extensively used in composite industries for
socioeconomic empowerment of peoples. The fabrication of coconut shell fibers based composites
using different matrixes has developed cost effective and eco-friendly biocomposites which directly
affecting the market values of coconut shell. To design such composites thorough investigation of
fundamental, mechanical, and physical properties of coconut shell fibers is necessary.
An addition of tamarind shell powder has opened up a new way for enhancement of the properties of
composite materials. The percentage of additive may be altered and tested. In our test result there is no
significant change in flexural property when tamarind shell powder was used as an additive with
coconut shell powder. But when tensile test is performed with addition of tamarind shell powder with
coconut shell powder it shows a tremendous increase in its load carrying capacity. The result obtained
shows about 50% increase in the strength of composite material upon adding tamarind shell powder.
Thus, this analysis has made an attempt to gather information for both basic properties of coconut shell
fiber based composites as well as their economic utilization. Current research on coconut shell fiber
based composite using both basic as well as applied science either in terms of modification, mechano-
physical, thermal and other properties. But, the ultimate goal of utilizing the coconut shell to its full
extent is far behind than its projected milestone. The sustainable future of coconut shell based
composite industry would help in utilizing the coconut shell in a way other than usual traditional
mode. The effective characterization of coconut shell fiber as well as coconut fiber based composites
should be more advance in terms of analysis and testing. In this review, we have tried to gather the
information about the analysis and testing methods used. However, researcher already done lots of
work on coconut shell based composites, but it still required to do more research and innovation in this
area to overcome potential challenges ahead. These things will make life easy for both urban as well as
rural people who are more depended on synthetic based composites.

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IOP Conf. Series: Materials Science and Engineering 376 (2018) 012105 doi:10.1088/1757-899X/376/1/012105
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[2] Nguong C W et al. 2013 A Review On Natural fiber Reinforced Polymer CompositesInt. J. of
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[3] Xue Li and Lope G 2007 Chemical Treatments of Natural Fiber for Use in Natural Fiber-
Reinforced Composites. A Review J Polym Environ. 10 25-33.
[4] John DVenables. 2015 Polymer matrix-compositesMaterials science11 27-33.
[5] Salmah H et al. 2012Surface Modulation of Coconut Shell Powder Filled Polylactic Acid
BiocompositesJ. of Thermoplastic Composite Material26 (6) 809-819.
[6] Hayder Abbas Sallal 2014 Effect of the Addition Coconut Shell Powder on Properties of
Polyurethane Matrix Composite. Al-Nahrain University, College of Engineering Journal17(2)203-210
[7] OlumuyiwaAgunsoye et al. 2012 Study of Mechanical Behaviour of Coconut Shell Reinforced
Polymer Matrix CompositeJ. of Minerals & Materials Characterization &Engg.11 774-779
[8] Srinivas K Ret al. 2012 Experimental Investigation of Mechanical Properties for Tamarind Shell
Particles as Filler in Epoxy Composite Int. J. of Engg. Research and Advanced Tech. 8 2454-6135