Composite Leaf Spring

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 1534
COMPOSITE LEAF SPRING
Sandeep Bhattacharjee¹, Suyog Kanitkar², Naveen Kalasapur³, Vivek Patel4
1,2,3,4 Department of Mechanical Engineering, KLE Institute of Technology, Hubli, Karnataka, India.
--------------------------------------------------------------***-------------------------------------------------------------
Abstract: The Automobile Industry has shownkeeninterest
for replacement of steel leaf spring with that of fiber
composite leaf spring, since the composite material has high
strength to weight ratio, good corrosion resistance andtailor-
able properties. They are found to be the potential materials
for replacing these conventional metallic leaf springs without
giving up the strength and by reducing the structural weight
substantially. Therefore, analysis of the composite material
becomes equally important to studythebehaviorofComposite
Leaf Spring. The aim is to review the paper about fabrication
and analysis of composite leaf spring. The numerical analysis
is carried via finite element analysis using ANSYS software.
Key Words: Composite material, Leaf Spring, High strength
to weight ratio, Optimum cost, Stress in leaf spring
1. INTRODUCTION
In the present scenario, to optimize the utilization of
energy, weight reduction became one of the main focuses of
automobile manufacturers. Weight reduction can be
achieved by the introduction of better material. Leaf springs
are mainly used in suspensionsystems toabsorbshock loads
in automobiles like light motor vehicles, heavy duty trucks
and in rail systems. They carry lateral loads, brake torque,
driving torque in addition to shock absorbing. Leaf springs
are having an advantage that the ends of the spring may be
guided along a definite path as it deflects. The use of
composite materials for suspension leaf spring reduces the
weight of conventional multi leaf steel leaf spring by nearly
75%.This achieves the vehicle with more fuel efficiency and
improved riding qualities. For more compliant suspension
system (i.e. energy storage capability), theleafspringshould
absorb the vertical vibrations and impacts due to road
irregularities by means of variations in the spring deflection
so that the potential Energy is stored in spring as strain
energy and then released slowly. A material with maximum
strength and minimum modulus of elasticity in the
longitudinal direction is the most suitable material for a leaf
spring. The composite materials have more elastic strain
energy storage capacity, excellent corrosion resistance,high
strength to weight ratio as compared with those of steel.
Conventional Multi-leaf steel springs are being replaced by
mono-leaf composite springs.
Fatigue failure is the predominant mode of in-service
failure of many automobile components. This is due to the
fact that the automobile components aresubjectedtovariety
of fatigue loads like shocks caused due to road irregularities
traced by the road wheels, the sudden loadsduetothewheel
travelling over the bumps etc. The leaf springs are more
affected due to fatigue loads, as they are a part of the
unstrung mass of the automobile.
In the present work comparative study is been carried
out to understand the working principle of multi-leaf steel
spring used in passenger cars. The multi-leaf steel spring is
replaced with a composite single leafspringmadeofEglass/
epoxy and Jute-Glass fiber composite. The stresses for both
steel leaf spring and composite leaf springs are considered
for the study. The primary objective is to compare their load
carrying capacity, stiffness and weight savings of composite
leaf spring. Finally, Natural frequencies and fatigue life of
Natural Faber reinforced composite leaf spring is also
predicted using life data.
2. LITERATURE SURVEY
2.1 Preceding Studies:
1. V.K. Aher et. al. “Fatigue Life Prediction of Multi Leaf
Spring used in the Suspension System of Light Commercial
Vehicle”, International Journal on Theoretical and Applied
Research in Mechanical Engineering (IJTARME), 2012.
The purpose of this paper is to predict the fatigue
life of steel leaf spring along with analytical stress and
deflection calculations. This present work describes static
and fatigue analysis of a steel leaf spring of a light
commercial vehicle (LCV).The non-linear static analysis of
2D model of the leaf spring is performed using NASTRAN
solver and compared with analytical results. The pre-
processing of the model is done by using HYPERMESH
software. The stiffness of the leaf spring is studied by
plotting load versus deflection curve for various load
applications. The simulation results are compared with
analytical results. The fatigue life of the leaf spring is
predicted using MSC Fatigue software.
2. Ravi Kumar V. et. al. “Analysis of Natural Fibre Composite
Leaf Spring”, International Journal of Latest Trends in
Engineering and Technology (IJL2TET) September 2013
The aim of present work is to compare the Glass-
Fiber-Reinforced - Composite (GFRC) leaf spring with a
Natural-Fiber-ReinforcedComposite/Jute-Fiber– Reinforced
– Composite (NFRC/JFRC) leaf spring. Fabrication is carried
by hand lay-up technique and tested. The present work

carries analytical and simulated results comparison of both
types of composite leaf springs. The testing was performed
experimentally with the help of Universal Testing Machine
(UTM) and by Finite Element Analysis (FEA) using ANSYS.
Stresses and Deflection were verified with analytical and
experimental results. Compared to the GFRC leaf spring, the
NFRC Composite material spring has stresses muchlower to
steel and the spring weight is also reduced nearly to 60-
70%.The
3. T.N.V. Ashok Kumar at. al. “Design and Material
Optimization of Heavy Vehicle Leaf Spring”, International
Journal of Research in Mechanical Engineering &
Technology, Nov 2013 - April 2014
The paper describes static and dynamic analysis ofsteel
leaf spring and laminated composite Multi leaf spring. The
objective is to compare displacement, frequencies,
deflections and weight savings of composite leaf springwith
that of steel leaf spring. Static and Dynamic Analysis of 3-D
model of conventional leaf spring is performed using ANSYS
10.0. Same dimensions are used in composite multi leaf
spring using S2 Glass/Epoxy and Kevlar/Epoxy
unidirectional laminates. Analysis is done by layer stacking
method for composites bychangingreinforcementangles for
3 layers, 5 layers and 11 layers. The weight of compositeleaf
spring is compared with that of steel leaf spring. The design
constraints are stresses and deflection.Aweight reductionof
27.5 % is achieved by using composite leaf spring.
3. APPLICATIONS
A leaf spring is a simple form ofspringcommonlyusefor
the suspension in wheeled vehicles. Originally called a
laminated or carriage spring, and sometimes referredtoasa
semi-elliptical spring or cart spring, it is one of the oldest
forms of springing, dating back to medieval times.
A leaf spring takes the form of a slender arc-shaped
length of spring steel ofrectangularcross-section. Thecenter
of the arc provides location for the axle, while tie holes are
provided at either end for attaching to the vehicle body. For
very heavy vehicles, a leaf spring can be made from several
leaves stacked on top of each other in several layers, often
with progressively shorter leaves. Leaf springs can serve
locating and to some extent damping as well as springing
functions. While the interleaf friction provides a damping
action, it is not well controlled and results in stiction in the
motion of the suspension. For this reason some
manufacturers have used mono-leaf springs.
A leaf spring can either be attached directly to theframe
at both ends or attached directly at one end, usually the
front, with the other end attached through a shackle, a short
swinging arm. The shackle takes up the tendency of the leaf
spring to elongate when compressed and thus makes for
softer springiness. Some springs terminated in a concave
end, called a spoon end (seldom used now), to carry a
swivelling member.
3.1 Contents
3.1.1 History
3.1.2 Characteristics.
3.1.3 Manufacturing Process
3.1.1 History
There were a variety of leaf springs, usually employing the
word "elliptical". "Elliptical" or "full elliptical" leaf springs
referred to two circular arcs linked at their tips. This was
joined to the frame at the top center of the upper arc, the
bottom center was joined to the "live" suspension
components, such asa solidfrontaxle.Additional suspension
components, such as trailing arms, would usually be needed
for this design, but not for "semi-elliptical" leaf springs as
used in the Hotchkiss drive. That employed the lower arc,
hence its name. "Quarter-elliptic" springs often had the
thickest part of the stack of leaves stuck into the rear end of
the side pieces of a short ladder frame, with the free end
attached to the differential, as in the Austin Seven of the
1920s. As an example of non-elliptic leaf springs, the Ford
Model T had multiple leaf springs over its differential that
were curved in the shape of a yoke. As a substitute for
dampers (shock absorbers), some manufacturers laid non-
metallic sheets in between the metal leaves, such as wood.
Fig.3.1 Varieties of Leaf Springs
Elliptic
Semi-elliptic
Three quarter-elliptic
Quarter-elliptic
Transverse

Leaf springs were very common on automobiles,
right up to the 1970s in Europe and Japan and late '70s in
America when the move to front-wheel drive, and more
sophisticated suspension designs saw automobile
manufacturers use coil springs instead. Today leaf springs
are still used in heavy commercial vehicles such as vans and
trucks, SUVs, and railway carriages. For heavy vehicles, they
have the advantage of spreading the load more widely over
the vehicle's chassis, whereas coil springs transfer it to a
single point. A further advantage of a leaf spring over a
helical spring is that the end of the leaf spring may be guided
along a definite path.
A more modern implementationistheparabolic leaf
spring. This design is characterized by fewer leaves whose
thickness varies from center to ends following a parabolic
curve. In this design, inter-leaf friction is unwanted, and
therefore there is only contact between the springs at the
ends and at the center where the axle is connected. Aside
from a weight saving, the main advantage of parabolic
springs is their greater flexibility, which translates into
vehicle ride quality that approaches that of coil springs. It is
widely used on buses for better comfort. A further
development by the British GKN company and by Chevrolet
with the Corvette amongst others, is the move to composite
plastic leaf springs.
Typically when used in automobile suspension the leaf
both supports an axle and locates/ partially locates the axle.
This can lead to handling issues (such as 'axle tramp'),asthe
flexible nature of the spring makes precise control of the
unsprung mass of the axle difficult.Somesuspensiondesigns
use a Watts link (or a Panhard rod) and radiusarmstolocate
the axle and do not have this drawback. Suchdesignscanuse
softer springs, resulting in better ride. The various Austin-
Healey 3000's and Fiat 128's rear suspension are examples.
3.1.2 Characteristics
1. The leaf spring acts as a linkage for holding the axle in
position and thus separate linkage are not necessary. It
makes the construction of the suspensionsimpleandstrong.
2. As the positioning of the axle is carried out by the leaf
springs so it makes it disadvantageous to use soft springsi.e.
a spring with low spring constant.
3. Therefore, this type of suspension does not provide good
riding comfort. The inter-leaf friction between the leaf
springs affects the riding comfort.
4. Acceleration and braking torque cause wind-up and
vibration. Also wind-up causes rear-end squat and nose-
diving.
5. The inter-leaf friction damps the spring's motion and
reduces rebound, which until shock absorbers were widely
adopted was a great advantage over helical springs.
3.1.3 Manufacturing Process
Multi-leaf springs are made as follows:
1. Shearing of flat bar
2. Center hole punching / Drilling
3. End Heating process forming (hot & cold process)
1. Eye Forming / Wrapper Forming
2. Diamond cutting / end trimming / width
cutting / end tapering
3. End punching / end grooving / end
bending / end forging / eye grinding
4. Center hole punching / Drilling / nibbing
4. Heat Treatment
1. Heating
2. Camber forming
3. Hardening
4. Quenching
5. Tempering
5. Surface preparation
1. Shot peening / stress peening
2. Primary painting
6. Eye bush preparation process
1. Eye reaming / eye boring
2. Bush insertion
3. Bush reaming
4. DESIGN OF LEAF SPRING
The relationship of the specific strain energy canbe
expressed as it is well known that springs, are designed to
absorb and store energy and then release it slowly.Ability to
store and absorb more amount of strain energy ensures the
comfortable suspension system.
Fig 4.1 Standard and Parabolic Leaf Spring

4.1 Terms Involved:
1. Span: Horizontal Distance between the Eyes of spring.
2. Main Leaf: The Long leaf fastened tothesupportsiscalled
main leaf or master leaf.
3. Eye: Main leaf ends are bent to form the Eyes.
4. Camber: Distance b/w horizontal axis joining 2 eyes and
main leaf.
5. Auxiliary Leaves: Other leaves below main spring are
called Graduated leaves.
Fig 4.2 Laminated Leaf Spring
Fig 4.3 Reaction forces on the spring eyes in the
vehicle
Fig 4.4 Active and Reactive Forces on spring
The relationship of the specific strain energy can be
expressed as,
Where,
σ is the strength, ρ is the density
E is Young’s Modulus of the spring material.
2. Increased weight.
3. Conventional leaf springs are usually manufactured and
assembled by using number of leafs made of steel and hence
the weight is more.
4. Its corrosion resistance is less compared to composite
materials.
5. Steel leaf springs have less damping capacity.
4.3 SELECTION OF COMPOSITE MATERIAL
A composite material is defined as a material
composed of two or more constituents combined on a
macroscopic scale by mechanical and chemical bonds.
Composites are combinations of two materials in which one
of the material is called the “matrix phase” is in the form of
fibres, sheets, or particles and is embedded in the other
material called the “reinforcing phase”. Many composite
materials offer a combination of strength and modulus that
are either comparable to or better than any tradional
metallic metals. Because of their low specific gravities, the
strength to weight-ratio and modulus to weight-ratios of
these composite materials are markedly superiortothose of
metallic materials. The fatigue strength weightratios aswell
as fatigue damage tolerances of many composite laminates
are excellent. For these reasons, fibre composite have
emerged as a major class of structural material and are
either used or being considered as substitutions for metal in
many weight-critical components in aerospace, automotive
and other industries. Another unique characteristic of many
fibre reinforced composites is their high internal damping
capacity. This leads to better vibration energy absorption
within the material and results in reduced transmission of
noise to neighbouring structures. High damping capacity of
composite materials can be beneficial in many automotive
applications in which noise, vibration, and hardness is a
critical issue for passenger comfort.
The ability to absorb and store more amount of
energy ensures the comfortable operation of a suspension
From the above equation, the material which is
having low density and low Young’s modulus will have high
strain energy storage capacity. This purpose will be served
by Composites.
4.2 DEMERITS OF CONVENTIONAL LEAF SPRING
1. They have less specific modulus and strength.

system. However, the problem of heavy weight of spring is
still persistent when using steel leaf spring. This can be
remedied by introducing composite material insteadofsteel
which is normally used in the conventional leaf spring. It is
well known that springs are designed to absorb and store
energy and then release it.
Hence, the strain energy of the material becomes a major
factor in designing the springs.
It can be easily observed that material havinglowermodulus
and density will have a greater specific strain energy
capacity. Research has indicated that E-Glass/Epoxy has
good characteristics for storingspecific strainenergy.Hence,
E Glass/Epoxy is selected as the composite material.
5. CASE STUDY
5.1 Modelling and Analysis ofLaminated CompositeLeaf
Spring under the Static Load Conditions by using FEA
In the present work, the dimensions of an existing
mono steel leaf spring of a Maruti 800 passenger vehicle is
taken for modelling and analysis of a laminated composite
mono leaf spring with three different composite materials
namely, E-glass/Epoxy, S-glass/Epoxy and Carbon/Epoxy
subjected to the same load as that of a steel spring. The
design constraints were stresses and deflections. The three
different composite mono leaf springs have been modelled
by considering uniform cross-section, with unidirectional
fiber orientation angle for each lamina of a laminate. Static
analysis of a 3-D model has been performed using ANSYS
10.0. Compared to mono steel leaf spring the laminated
composite mono leaf spring is found to have 47% lesser
stresses, 25%~65% higher stiffness, 27%~67% higher
frequency andweightreductionof73%~80%isachieved[1].
Table 5.1 shows the specifications of a mono leaf
steel spring of a maruti 800 passenger vehicle. The typical
chemical composition of the material is 0.565C, 1.8% Si,
0.7%Mn, 0.045%P and 0.045% S.
Table 5.1: Specifications of Mono Leaf Steel Spring
Sl. No. Parameters Value
1 Total length of the spring(Eye
to Eye)
965mm
2 Free camber (At no load
condition)
6mm
3 No. of full length leave
(Master Leaf)
01
4 Thickness of leaf 10mm
5 Width of leaf spring 50mm
6 Maximum load given on 794.54N
spring
7 Young’s Modulus of leaf
spring
2.1e5 N/mm2
Deflection of leaf spring:
𝛅= [1]
Where,
W- Maximum load on leaf spring
L- Total length of the spring (Eye to Eye)
E- Young’s Modulus of leaf spring
b- Width of leaf spring
t- Thickness of leaf
nG – number of graduated leaves
nF -- number of full length leaves
Fig 5.1 Stress distribution for steel leaf spring
Fig 5.2 Displacement pattern for steel leaf spring

Fig 5.3 Stress distribution for E-glass/epoxy laminated
composite leaf spring
Fig 5.4 Displacement pattern for E-glass/epoxy
laminated composite leaf spring
Fig 5.5 Stress distribution for S-glass/epoxy laminated
Fig 5.6 Displacement pattern for S-glass/epoxy
Fig 5.7 Stress distribution for carbon/epoxy laminated
Fig 5.8 Displacement pattern for carbon/epoxy

Fig 5.9 Load and Von-Mises Stress for Steel and
Laminated Composite Leaf Spring
Fig 5.10 Load- Deflection Curves for Steel and
Laminated Composite Leaf Spring
Table 5.2: Comparative Analysis of Mono Leaf Steel
Spring and Laminated Composite Leaf Spring
Sl.
No
Parameters
Steel
Spring
Laminated Composite Leaf
Spring
Comp1 Comp2 Comp3
1 Weight(kg) 3.79 1.01 0.965 0.762
2
Stress
(N/mm2)
498.19 256.05 256.320
262.56
0
5.2 MERITS OF COMPOSITE LEAF SPRING
1. Reduced weight.
2. Due to laminate structure and reduced thickness of the
mono composite leaf spring, the overall weight would be
less.
3. Due to weight reduction, fuel consumption would be
reduced.
4. They have high damping capacity; hence produce less
vibration and noise.
5. They have good corrosion resistance [5].
6. CONCLUSION
A comparative study has been made between
laminated composite leaf spring and steel leaf spring with
respect to weight, stiffness and strength. By employing a
composite leaf spring for the same load carrying capacity,
there is a reduction in weight of 73%~80%, natural
frequency of composite leaf springs are 27%~67% higher
than steel leaf spring and 23~65% stiffer than the steel
spring. Based on the results, it was inferred that
carbon/epoxy laminated composite mono leaf spring has
superior strength and stiffness and lesser in weight
compared to steel and other compositematerialsconsidered
in this investigation.
From the results, it is observed that the laminated
composite leaf spring is lighter and more economical than
the conventional steel spring with similar design
specifications [1]
The composite leaf spring is lighter than
conventional steel leaf spring with similar design
specifications but not always is cost- effective over their
steel counterparts. Composite materials have more elastic
strain energy storage capacity and high strength to weight
ratio as compared with those of steel. Therefore, it is
concluded that composite leaf spring is an effective
replacement for the existing steel leaf spring in automobile.
7. REFERENCES
1. M. Raghavedra et. al. “Modelling and Analysis of
Laminated Composite Leaf under the Static Load
Condition by using FEA”, International Journal of
Modern Engineering Research (IJMER) Vol.2, Issue.4,
July-Aug. 2012 pp-1875-1879
2. V.K. Aher et. al. “Fatigue Life Prediction of Multi Leaf
Spring used in the Suspension System of Light
Commercial Vehicle”, International Journal on
Theoretical and Applied Research in Mechanical
Engineering (IJTARME), 2012.
3. Ravi Kumar V. et. al. “Analysis of Natural Fibre
Composite Leaf Spring”, International Journal of Latest
Trends in Engineering and Technology (IJL2TET)
September 2013
4. T.N.V. Ashok Kumar at. al. “Design and Material
Optimization of Heavy Vehicle Leaf Spring”,
International Journal of Research in Mechanical
Engineering & Technology, Nov 2013 - April 2014

5. Pankaj Saini et. al. “DESIGN AND ANALYSIS OF
COMPOSITE LEAF SPRING FOR LIGHT VEHICLES”,
International Journal of Innovative Research in Science,
Engineering and Technology. Vol. 2, Issue 5, May 2013
6. Baviskar A. C. et. al. “Design and Analysisofa LeafSpring
for automobile suspension system: A Review”,
International Journal of Emerging Technology and
Advanced Engineering Website: www.ijetae.com (ISSN
2250-2459, ISO 9001:2008 Certified Journal, Volume 3,
Issue 6, June 2013)
7. Ravi Kumar V. et. al. “Analysis of Natural Fiber
Composite Leaf Spring”, International Journal of Latest
Trends in Engineering and Technology (IJLTET) Vol. 3
Issue 1 September 2013
8. V Sampath et. al. “ANALYSIS OF LEAF SPRING WITH
VARIABLE THICKNESS FOR COMPOSITE MATERIALS”,
International Journal For Technological Research In
Engineering Volume 1, Issue 9, May-2014

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