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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 6, June 2017, pp. 544–552, Article ID: IJMET_08_06_057
Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=6
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
DESIGN AND ANALYSIS OF COCONUT FIBER
REINFORCED POLYESTER COMPOSITE LEAF-
SPRING
Narendiranath Babu T, Bandaru Shivasai, Vattikuti Mahesh, Prashant Reddy
VIT University, Vellore, Tamilnadu, India
ABSTRACT
In today's world, the need for automobiles matches the need for their weight
reduction. This led the inventors and researchers to an alternative solution,
composites. Composites are known for their strength and light weight. Composite
properties are the hybrid properties of two or more materials that mainly contain
reinforcement and matrix. One of the reinforcement that is available in abundant in
nature is Coir (coconut fibre). In this project we demonstrate the design and analysis
of a leaf spring which is made up of coir reinforced polyester matrix composite. The
main objective of this project is to reduce the weight of an automobile by replacing its
steel leaf spring with composite leaf spring that would produce same deflection when
the load applied is constant and compare its relative merits and demerits. The
modelling of leaf-springs is done using SOLIDWORKS and analysis is done using
ANSYS.
Key words: design; analysis; coir; composite; polyester; leaf-spring; weight reduction.
Cite this Article: Narendiranath Babu T, Bandaru Shivasai, Vattikuti Mahesh,
Prashant Reddy. Design and Analysis of Coconut Fiber Reinforced Polyester
Composite Leaf-Spring. International Journal of Mechanical Engineering and
Technology, 8(6), 2017, pp. 544–552.
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=6
1. INTRODUCTION
A lot of research has been done on composite leaf-springs. The authors were successful in
proving that composites can replace the conventional steel springs. Before implementing the
idea of using Coir as reinforcement, it would be helpful to go through the research work that
has already been done in these fields. Though much research was not available in the field of
coir composites, the available content was enough to produce this paper. P N E Naveen and T
Dharmaraju fabricated and presented the properties of various samples with different fiber
compositions in their paper [9].In work by D.Verma, he mentioned the use of natural fibre as
the reinforcement for composites in his paper. He compared the compositions of various kinds
of natural fibres. He presented his study on the annual availability of natural fibres. He
concentrated his study on to coir and presented the chemical composition of Coir [7]. In a
thesis submitted by Sonu Abhishek (NIT Rourkela), he compared the compositions of natural
Narendiranath Babu T, Bandaru Shivasai, Vattikuti Mahesh, Prashant Reddy
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fibres. He presented the production of natural fibres. He fabricated and evaluated the
properties of coir fibre reinforced epoxy composites. He also studied the dependence of
strength of composite on the length of coir fibre.In another thesis submitted by Vineeth
Kumar Bhagat (NIT Rourkela), he compared the physical properties of few natural fibres and
E glass epoxy. He fabricated different samples with different compositions of class fibre and
coir fibre and evaluated their mechanical properties.In a work done by S.Pichi Reddy he
fabricated epoxy resin and e glass fibre composite using different compositions of fly ash and
resin and compared the mechanical properties of the different samples [17].In a work done by
Chizoba Obele, the author fabricated coir reinforced epoxy resin composites with different
composition of filler loading and evaluated their mechanical properties. Using the above
results they fabricated a helmet shell made using 30% wt. Composition of filler material [4].In
a thesis submitted by Janaki Dehury, the author fabricated composites with different
composition of jute and glass fiber arranged in different orientations. Author presented his
study on their mechanical properties. In a paper presented by S.Ramakrishnan theoretically
predicted the mechanical behavior of natural fiber reinforced vinyl ester composites. He,
using ANSYS evaluated their mechanical properties. Different samples with different weight
fractions of banana sisal and cotton were studied. Their toughness and impact strength were
compared [3].In a paper presented by Ajay B.K., he designed and analyzed the leaf spring
with different arrangement of composite leaves with steel leaves. He using ANSYS have
compared the properties of different leaf springs which have steel and composite leaf springs
arranged in different manners [5].
2. NOMENCLATURE
E Young’s Modulus
W Width of leaf spring
T Thickness of leaf spring
L Length of leaf spring
P Load acting on the spring.
SLS Steel leaf-spring
CLS Composite leaf-spring
One of the natural fibers which is available in abundant in nature and also very cheap,
Coir, is used as the reinforcement for polyester in this composite. Coir is a fiber, obtained
from various parts of coconut tree like coconuts and at leaves. It is well treated with salt water
and rinsed with chemicals to make it dust free. It is then cut in to required size. Composite
properties are taken from the journal published by P N E Naveen and M Yasasvi [5].
Figure 1 Coir fiber.
Design and Analysis of Coconut Fiber Reinforced Polyester Composite Leaf-Spring
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3. METHODOLOGY
Firstly for reference sake, a normal steel leaf-spring was modelled using Solidworks. It was
analyzed using Ansys to note its properties. The composite leaf-spring was modelled
according to the dimensions which give same deflection as that of steel leaf-spring when same
load is applied. It was then analyzed and the results are compared.
The detailed procedure, right from fabricating steel spring to arriving at the results is
presented in a step by step manner for easy understanding and future reference.
3.1. Design of Steel Leaf-Spring
For reference and comparison sake a general leaf-spring of six leaves, including four
graduated leaves, is modelled using Solidworks. The dimensions of steel Leaf-spring are
given in the table 1 and properties of steel are given in table 2.
Table 1 Dimensions of steel leaf spring.
Leaf type Length (mm) Width(mm) Thickness(mm)
Master leaf (eye to eye) 1000 32 14
Full length leaf 1014 32 14
I Graduated leaf
II Graduated leaf
III Graduated leaf
IV Graduated leaf
950
797
635
463
32
32
32
32
14
14
14
14
Table 2 Properties of Steel.
Property Value
Density 7850kg/m2
Tensile Yield Strength 250 MPa
Poisson’s ratio
Young’s modulus
0.3
210 GPa
Figure 2 Drafted model Figure 3 CAD model of leaf-spring.
3.2. Analysis of Steel Leaf-Spring
The CAD model is saved in IGES format and the same is imported in to Ansys. The leaf-
spring is given the properties of Structural steel. Constraints were set accordingly and a force
of 1000N is applied at the bottom plate. One side of the spring is arrested in all directions and
Narendiranath Babu T, Bandaru Shivasai, Vattikuti Mahesh, Prashant Reddy
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other side is allowed to move in one direction (X-axis). Meshing is done and solved for stress
and deformation in Y-axis
Table 3 Analysis results of SLS
Property Value
Load applied 1000 N
Maximum deformation 0.098375mm
Maximum stress produced
Weight of Leaf spring
14.616 MPa
19.603 Kg
Figure 4 Max. Stress distribution Figure 5 Max. Deformation.
3.3. Dimensions of Composite Leaf-Spring
The dimensions of composite leaf spring are set in such a way that, when 1000N is applied,
the deflection should be same as that of steel leaf-spring. For dimensions, a formula for PSG
Design Data Book is used to obtain the nearest value of thickness.
3
36
Enbt
PL=δ
�- deflection (mm)
P- semi-load (N)
L- semi-length (mm)
E-Young’s modulus (Pa)
n- Number of leaves
b- Breadth of leaf-spring (mm)
t- Thickness of leaf-spring (mm)
Firstly, length of 1.35m (end to end) and thickness of 16mm is fixed and width is
calculated using above formula The properties of the coir composite are taken from the source (ref. paper .1) and Poisson’s ratio is assumed to
be 0.3. The properties of composite are as follows.
Design and Analysis of Coconut Fiber Reinforced Polyester Composite Leaf-Spring
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Table 4 Properties of Coir composite
Property Value
Density 1380 kg/m^3
Tensile Yield Strength 25 MPa.
Poisson’s ratio
Young’s modulus
0.3
315 GPa
Density of coir fiber is calculated as
Density of coir (volume fraction of coir in composite)
+Density of polyester (volume fraction of polyester in composite)
DOC = 1200(0.10) +1400(0.90) = 1380kg/m^3
By equating the deflection of steel and composite spring, we get
Approximately, width = 35 mm
3.4. Design of composite leaf-spring
A leaf spring is modelled according to the dimensions obtained above but the deflection
obtained is 0.0928, which is not comparable to the required deflection. Now, as the deflection
is inversely proportional to width, width is assumed to be 18mm and is gradually increased till
35mm.
Different springs are modelled and analyzed for deflection. The values are tabulated as
follows.
Table 5 Width vs. Deflection graph
Width Deflection
18 0.163
22 0.136
26
30
35
0.115
0.104
0.093
Above data is clearly, not following a linear pattern, so a cubical plot (best fit) is made.
The graph is obtained as follows.
Figure 6 Width vs Deflection graph for composite spring.
y = -51611x3 + 22498x2 - 3403x + 198.46
0
5
10
15
20
25
30
35
40
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18
Width Vs Deflection
Narendiranath Babu T, Bandaru Shivasai, Vattikuti Mahesh, Prashant Reddy
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From the graph, for the deflection of .098 the width is obtained as 32.41 mm
The nearest width, 32 mm is considered.
The composite leaf-spring is designed with following dimensions
Table 6 Dimensions of composite leaf spring.
Leaf type Length (mm) Width(mm) Thickness(mm)
Master leaf(eye to eye) 1309.5 32 16
Full length leaf 1319.68 32 16
I Graduated leaf
II Graduated leaf
III Graduated leaf
IV Graduated leaf
1245.74
1059.86
852.79
627.01
32
32
32
32
16
16
16
16
3.5. Modelling of Composite Leaf-Spring
Once the dimensions of composite leaf-spring are obtained, we went on to model the leaf-
spring. The drafted view and model view of the leaf-spring are provided in the figures
Figure 7 Drafted model Figure 8 CAD model of leaf-spring.
3.6. Analysis of Composite Leaf Spring
The composite leaf-spring is analyzed by giving constraints and the results obtained are as
follows.
Figure 9 Max. Stress distribution. Figure 10 Max. Deformation
Design and Analysis of Coconut Fiber Reinforced Polyester Composite Leaf-Spring
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Table 7 Analysis results of CLS
Property Value
Load applied 1000 N
Maximum deformation 0.09727mm
Maximum stress produced
Weight of Leaf spring
12.22 MPa
5.152 Kg
4. RESULTS & DISCUSSIONS
4.1. Weight and Stress Comparison
The analysis results of both the springs are tabulated as shown in the following table for easy
comparison.
Table 8 Analysis results of CLS
Property SLS CLS
Load applied 1000 N 1000 N
Maximum deformation 0.098375mm 0.09727mm
Maximum stress produced
Weight of Leaf spring
14.616 MPa
19.603 Kg
12.22 MPa
5.152 Kg
Figure 11 Graph that presents the weight and stress reduction in composite leaf spring.
4.2. Stress for Different Loads
The variations in stress for both CLS and SLS are found using Ansys and are presented
in the form of graph.
Figure 11 Load vs. stress of both SLS and CLS
Narendiranath Babu T, Bandaru Shivasai, Vattikuti Mahesh, Prashant Reddy
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4.3. Verification of Cubic Plot
When the deflections of both, CLS and SLS are compared at different loads, we can test the
applicability of cubic plot.
Figure 9 Deflection comparison of CLS and SLS
The deflections of both, CLS and SLS are comparable even when different loads are
applied. The slight difference was due to rounding off 32.4 to 32.
5. CONCLUSIONS
Under the same static load and deflection conditions, both composite and steel leaf springs
show great difference in their weights. The weight of steel spring is very high compared to
that of composite. The weight of steel spring is 19.6 kgs whereas weight of composite spring
is 5 kgs. The induced stress of composite leaf spring is 12.22 MPa which is less than 14.616
MPa, the deflection of steel spring. Composite leaf spring can be used in light weight
vehicles, where weight is an important factor, whereas steel spring can be used in budget cars
for its low cost of manufacturing.
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