Final Report

Performance Analysis Of Epoxy Resin Based Composite Leaf Spring With E-Glass Fiber

CONTENTS

SR. No.

Description Page No.

1 INTRODUCTION

1.1 Overview of composites

1.2 Merits & Demerits of Composite

1.3. Scope of the project

2 LITERATURE SURVEY

2.1 Objectives of the Present Work

3 MATERIALS AND METHODS

3.1. Introduction

3.2. Characterization of the Composites

3.3. Processing of the Composites

4 RESULTS & ANALYSIS

4.1 Result & Discussion

4.2. Design Parameter for Composite Leaf Spring

4.3. Design of experiments

6 CONCLUSIONS

6.1. Scope for Future Work

REFERENCES

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ABSTRACT

LIST OF ABBREVIATIONS

FEM – Finite Element Method

FEA –Finite Element Analysis

GFRP – Glass Fiber Reinforced Polymer

E – Modulus of Elasticity

G – Modulus of Rigidity

σ – Stress

µ – Poissons Ration

e – Strain

P – Applied load

M – Material

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CHAPTER-1

INTRODUCTION

1.1 General

In order to conserve natural resources and economize energy, weight reduction has been

the main focus of automobile manufacturers in the present scenario. Weight reduction can be

achieved primarily by the introduction of better material, design optimization and better

manufacturing processes. The suspension leaf spring is one of the potential items for weight

reduction in automobiles as it accounts for 10% - 20% of the unsprung weight. This achieves the

vehicle with more fuel efficiency and improved riding qualities. The introduction of composite

materials was made it possible to reduce the weight of leaf spring without any reduction on load

carrying capacity and stiffness. Since, the composite materials have more elastic strain energy

storage capacity and high strength to weight ratio as compared with those of steel, multi-leaf

steel springs are being replaced by mono-leaf composite springs. The composite material offer

opportunities for substantial weight saving but not always be cost-effective over their steel

counterparts.

Fiber-reinforced polymers have been vigorously developed for many applications, mainly

because of the potential for weight savings. Other advantages of using fiber-reinforced polymers

instead of steel are: (a) the possibility of reducing noise, vibrations and ride harshness due to

their high damping factors; (b) the absence of corrosion problems, which means lower

maintenance costs; and (c) lower tooling costs, which has favorable impact on the manufacturing

costs [1]. Springs are crucial suspension elements in cars, necessary to minimize the vertical

vibrations, impacts and bumps due to road regularities[2]. The functions of the suspension

springs for an automobile are to maintain a good control stability and to improve riding comfort

due to composite design and manufacturing, complications arise; for example, the change from

relatively isotropic-homogeneous steel alloys to anisotropic in homogeneous fiber reinforcement

plastic has not yet been achieved [3 & 4]. The behavior of steel leaf spring is non linear,

relatively high weight, and change in solid axle angle due to weight transfer specially during

cornering of vehicle, that will lead to over steer and directional instability under such situation it

is very difficult for driver to control vehicle, these are some defect of metallic leaf spring so

considering automobile development and importance of relative aspect such as fuel consumption,

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weight, riding quality, and handling, so development of new material is necessary in the

automobile industry. Recently, graphite and carbon fiber demonstrate its superiority over other

composite material however due to cost and availability limitation the present work restricted to

leaf spring made up of glass fiber and Epoxy resin.

Many papers were devoted to find spring geometry. The recently vehicle such as Ford,

and Volvo buses are using leaf spring made up of carbon fiber as it gives good advantage but

costly. So in this select glass fiber and general purpose resin for spring material on the basis of

cost factor and strength.

1.1. Overview of composites

Composite materials (or composites for short) are engineering materials made from two

or more constituent materials that remain separate and distinct on a macroscopic level while

forming a single component. There are two categories of constituent materials: matrix and

reinforcement. At least one portion of each type is required. The matrix material surrounds and

supports the reinforcement materials by maintaining their relative positions. The reinforcements

impart their special mechanical and physical properties to enhance the matrix properties. The

primary functions of the matrix are to transfer stresses between the reinforcing fibers/particles

and to protect them from mechanical and/or environmental damage whereas the presence of

fibers/particles in a composite improves its mechanical properties such as strength, stiffness etc.

A composite is therefore a synergistic combination of two or more micro-constituents that differ

in physical form and chemical composition and which are insoluble in each other. The objective

is to take advantage of the superior properties of both materials without compromising on the

weakness of either. The synergism produces material properties unavailable from the individual

constituent materials. Due to the wide variety of matrix and reinforcement materials available,

the design potentials are incredible. Composite materials have successfully substituted the

traditional materials in several light weight and high strength applications. The reasons why

composites are selected for such applications are mainly their high strength-toweight ratio, high

tensile strength at elevated temperatures, high creep resistance and high toughness. Typically, in

a composite, the reinforcing materials are strong with low densities while the matrix is usually a

ductile or tough material. If the composite is designed and fabricated correctly it combines the

strength of the reinforcement with the toughness of the matrix to achieve a combination of

desirable properties not available in any single 3 conventional material. The strength of the

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composites depends primarily on the amount, arrangement and type of fiber and /or particle

reinforcement in the resin.

They are:

a) Metal Matrix Composites (MMC)

b) Ceramic Matrix Composites (CMC)

c) Polymer Matrix Composites (PMC)

a) Metal Matrix Composites

Metal Matrix Composites have many advantages over monolithic metals like higher

specific modulus, higher specific strength, better properties at elevated temperatures, and lower

coefficient of thermal expansion. Because of these attributes metal matrix composites are under

consideration for wide range of applications viz. combustion chamber nozzle (in rocket, space

shuttle), housings, tubing, cables, heat exchangers, structural members etc.

b) Ceramic matrix Composites

One of the main objectives in producing ceramic matrix composites is to increase the

toughness. Naturally it is hoped and indeed often found that there is a concomitant improvement

in strength and stiffness of ceramic matrix composites.

c) Polymer Matrix Composites

Most commonly used matrix materials are polymeric. The reason for this are twofold. In

general the mechanical properties of polymers are inadequate for many structural purposes. In

particular their strength and stiffness are low compared to metals and ceramics. These difficulties

are overcome by reinforcing other materials with polymers. Secondly the processing of polymer

matrix composites need not involve high pressure and doesn’t require high temperature. Also

equipments required for manufacturing polymer matrix composites are simpler. For this reason

polymer matrix composites developed rapidly and soon became popular for structural

applications. Composites are used because overall properties of the composites are superior to

those of the individual components for example polymer/ceramic. Composites have a greater

modulus than the polymer component but are not as brittle as ceramics.

Two types of polymer composites are:

• Fiber reinforced polymer (FRP)

• Particle reinforced polymer (PRP)

Fiber Reinforced Polymer

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Common fiber reinforced composites are composed of fibers and a matrix. Fibers are the

reinforcement and the main source of strength while matrix glues all the fibers together in shape

and transfers stresses between the reinforcing fibers. The fibers carry the loads along their

longitudinal directions. Sometimes, filler might be added to smooth the manufacturing process,

impact special properties to the composites, and reduce the product cost. Common fiber

reinforcing agents include asbestos, carbon / graphite fibers,

beryllium, beryllium carbide, beryllium oxide, molybdenum, aluminium oxide, glass fibers,

polyamide, natural fibers etc. Similarly common matrix materials include epoxy, phenolic,

polyester, polyurethane, polyetherethrketone (PEEK), vinyl ester etc. Among these resin

materials, PEEK is most widely used. Epoxy, which has higher adhesion and less shrinkage than

PEEK, comes in second for its high cost.

Particle Reinforced Polymer

Particles used for reinforcing include ceramics and glasses such as small mineral

particles, metal particles such as aluminium and amorphous materials, including polymers and

carbon black. Particles are used to increase the modules of the matrix and to decrease the

ductility of the matrix. Particles are also used to reduce the cost of the composites.

Reinforcements and matrices can be common, inexpensive materials and are easily processed.

Some of the useful properties of ceramics and glasses include high melting temp., low density,

high strength, stiffness; wear resistance, and corrosion resistance. Many ceramics are good

electrical and thermal insulators. Some ceramics have special properties; some ceramics are

magnetic materials; some are piezoelectric materials; and a few special ceramics are even

superconductors at very low temperatures. Ceramics and glasses have one major drawback: they

are brittle. An example of particle reinforced composites is an automobile tire, which has carbon

black particles in a matrix of poly-isobutylene elastomeric polymer. Polymer composite

materials have generated wide interest in various engineering fields, particularly in aerospace

applications. Research is underway worldwide to develop newer composites with varied

combinations of fibers and fillers so as to make them useable under different operational

conditions. Against this backdrop, the present work has been taken up to develop a series of

PEEK based composites with glass fiber reinforcement and with ceramic fillers and to study their

response to solid particle erosion.

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The composite materials have got a widely applications in all cutting-edge ranges of

advanced materials as aeronautics, automotives, boats, sports parts and medical devices. As a

general definition, the composite material has more versions, and ones of them can be as a

material composed by the combination of two or more materials: a reinforcing element and a

compatible resin binder (matrix) to obtain specific characteristics and properties.

The roles of matrix in composite materials are to give shape to the composite part, protect

the reinforcements to the environment, transfer loads to reinforcements and toughness of

material, together with reinforcements. The aims of reinforcements in composites are to get

strength, stiffness and other mechanical properties, dominate other properties as coefficient of

thermal extension, conductivity and thermal transport.

1.2. Merits & Demerits of Composites

Advantages of composites over their conventional counterparts are the ability to meet

diverse design requirements with significant weight savings as well as strength-to-weight ratio.

Some advantages of composite materials over conventional are as follows: -

Tensile strength of composites is four to six times greater than that of steel.

Improved torsional stiffness and impact properties.

Lower embedded energy compared to other structural metallic materials like steel,

aluminum etc.

Composites are less noisy while in operation and provide lower vibration transmission

than metals.

Composites are more versatile than metals and can be tailored to meet performance needs

and complex design requirements.

Long life offer excellent fatigue, impact, environmental resistance and reduce

maintenance.

Composites enjoy reduced life cycle cost compared to metals. Composites exhibit

excellent corrosion resistance and fire retardancy.

Improved appearance with smooth surfaces and readily incorporable integral decorative

melamine are other characteristics of composites.

Composite parts can eliminate joints / fasteners, providing part simplification and

integrated design compared to conventional metallic parts.

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Broadly, composite materials can be classified into three groups on the basis of matrix

material.

Such as Demerits of composites are the followings:

Cost of materials

Long development time

Low ductility

Temperature limits

Solvent or moister attack

Hidden damages and damage susceptibility

1.2.3 E-Glass/Epoxy Data Sheet

Key Characteristics Test Method Units - English (SI) Typical Values

Specific Gravity -- lb./in. (g/cc) 0.064 (1.77)

Rockwell Hardness (.50”) -- M Scale 99

Tensile Strength (.125”) LW CW ASTM D-638 psi (MPa)

43,000 (296) 39,000 (269)

Compressive Strength, Flatwise (.50”)

ASTM D-695 psi (MPa) 44,000 (303)

Flexural Strength (.062”) LW CW ASTM D-790 psi (MPa) 66,000 (455) 60,000 (413)

Flexural Modulus (.062”) LW CW ASTM D-790 ksi (MPa)

3,400 (23,442) 3,300 (22,753)

Shear Strength, Perpendicular (.062”)

ASTM D-732 psi (MPa) 19,000 (130)

IZOD Impact Strength LW CW ASTM D-256 ft.-lbs./in. Notched 9.5 7.5

Dielectric Strength (.062”) Condition A D-48/50 ASTM D-149 V/mil 960 1,000

Breakdown Voltage (.062”) Condition A D-48/50 ASTM D-149 kV 66 65

1.3 Composites Applications

The advanced composite materials can be used for applications demand high strength,

high stiffness, or low thermal conductivity, which substituted many aerospace , aircrafts,

automotives, marines, constructions parts by metal with these composites .

Advanced composites contained materials such as carbon/graphite, boron or aramid

fibers in an organic resin matrix used by aerospace’s industries. The special properties of these

materials, examples lightweight, stiffness and strong materials are used from aircraft structures to

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automotive and trucks parts, from spacecraft to printed circuit boards, sports equipment, such as:

the gamut for boat hulls and hokey shine guards, advanced composite hinge for retractable arm

of space shuttle.

Carbon/graphite-reinforced composites are used in many applications, which required

thermal stability, high temperature strength, good ablation characteristics and insulating

capability.

Graphite fibers are used in place where required greater strength and higher thermal

conductivity, have six times the tensile strength of carbon fibers.

Carbon fibers are used in rocket nozzle thoughts and ablation chambers, because of them

physically stability and elevated temperature.

In generally, the composite materials can change with success the metal parts in diverse

application, for example will be analysis the altering of slide bearing of bimetallic material from

machine tools with bearing of composites, by used the finite element analysis (FEA).

1.4. Scope of the project

1. The basic aim of the present work is to develop and characterize a new class of composites

material with a polymer called epoxy-Resin as the matrix and glass fiber as the reinforcing

material.

2. Their physical and mechanical characterization is done.

3. Vibrational behavior of this new class of composites is investigated in this project work.

Deflection is performed on the composites material for leaf spring application.

4. This work is expected to introduce a new class of functional polymer composites suitable for

tribological & suspension applications.

1.3.1 Historical background

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CHAPTER 2

LITERATURE SURVEY

This chapter outlines some of the recent reports published in literature on composites

with special emphasis on erosion wear behavior of glass fiber reinforced polymer composites.

Polymers have generated wide interest in various engineering fields including tribological

applications, in view of their good strength and low density as compared to monolithic metal

alloys. Being lightweight they are the most suitable materials for weight sensitive uses, but their

high cost sometimes becomes the limiting factor for commercial applications. Use of low cost,

easily available fillers is therefore useful to bring down the cost of component. Study of the

effect of such filler addition is necessary to ensure that the mechanical properties of the

composites are not affected adversely by such addition. Available references suggest a large

number of materials to be used as fillers in polymers [5]. The purpose of use of fillers can

therefore be divided into two basic categories; first, to improve the mechanical, thermal or

tribological properties and second, to reduce the cost of the component. There have been various

reports on use of materials such as minerals and inorganic oxides, such as alumina and silica

mixed into widely employed thermoplastic polymers like polypropylene [6,7] and polyethylene

[8,9]. But very few attempts have indeed been made to utilize cheap materials like industrial

wastes in preparing particle-reinforced polymer composites. A key feature of particulate

reinforced polymer composites that makes them so promising as engineering materials is the

opportunity to tailor the materials properties through the control of filler content and matrix

combinations and the selection of processing techniques. A judicious selection of matrix and the

reinforcing solid particulate phase can lead to a composite with a combination of strength and

modulus comparable to or even better than those of conventional metallic materials [10]. Hard

particulate fillers consisting of ceramic or metal particles and fiber fillers made of glass are being

used these days to dramatically improve the wear resistance of composites, even up to 9 three

orders of magnitude [11]. The improved performance of polymers and their composites in

automobile applications by the addition of particulate fillers has shown a great promise and so

has lately been a subject of considerable interest. Various kinds of polymers and polymer matrix

composites reinforced with metal particles have a wide range of industrial applications such as

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heaters, electrodes [12], composites with thermal durability at high temperature [13] etc. These

engineering composites are desired due to their low density, high corrosion resistance, ease of

fabrication, and low cost [14, 15]. Similarly, ceramic filled polymer composites have been the

subject of extensive research in last two decades.

According to Roberts and M. INST B.E.(1954), there is no exaggeration to say that

springs are the life blood of modern civilized life, for without springs the great development

which has taken place in engineering and mechanical science would have been impossible.

Simple everyday actions, such as the latching or locking of a door, or turning on an electric light,

are controlled by springs. Springs are essential for working of clocks, watches, gramophone,

wireless, the intricate mechanism of automatic telephone, and the gigantic printing presses and

weaving looms. Modern travel would be impossible without springs, many thousands of different

types being used in bicycles, motor cycles, cars and aircraft.

Springs are unlike other machine/structure components in that they undergo significant

deformation when loaded; their compliance enables them to store readily recoverable mechanical

energy. It is well known that springs, in general, are designed to absorb and store energy and

then release it. Hence, the strain energy of the material and the shape become a major factor in

designing the springs (Al-Qureshi, 2001). In a vehicle suspension, when the wheel meets an

obstacle, the springing allows movement of the wheel over the obstacle and thereafter returns the

wheel to its normal position (i.e. to be resilient).

The elliptic composite springs described by Mallick (1987) represents the first step in

introducing fiber reinforced composite elliptic springs for automotive applications. Mechanical

performance and failure modes of composite elliptic spring elements under static load conditions

were also reported. Key design parameters, such as spring rate and failure load were measured as

a function of spring thickness.

Nowadays, the industrial vehicles have to reduce their tare weight and to improve safety

as well as life expectancy; one solution to this is the replacement of steel springs with composite.

As stated by Sardou and Djomseu (2000), there are three ways to introduce composite on vehicle

suspension. The first is to take away a metal leaf spring and put in place a composite leaf spring.

Second is to design a composite axle doing anti roll as well as spring and guidance task. The last

one is to design a metal suspension and to use composite spring only for its vehicle properties. First

and second solutions design the composite to carry a complex job of wheel control and suspension

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spring. The task is rather complex for composite and end up with a relatively small benefit in weight

and cost, on top of that suspension quality is relatively poor. However, in the field of vehicle

suspension, the industry looks for a cost effective composite spring with minimum mass capable of

resisting corrosion and possessing a high degree of durability. Therefore, the automobile industry has

shown increased interest in the replacement of steel springs with composite springs especially glass

fibre composites rather than others such as carbon fiber due to the cost factor.

Testing of Steel and Composite Mono Leaf Spring [23]

The steel and composite leaf springs are tested in the Leaf spring test rig. The experimental set

up is shown in Figs.2 (a) and (c). The leaf springs are tested following

standard procedures recommended by SAE. The spring to be tested is examined for any

defects like cracks, surface abnormalities, etc. The spring is loaded from zero to the prescribed

maximum deflection and back to zero. The load is applied at the centre of spring; the vertical

deflection of the spring centre is recorded in the load interval of 50N.

Fig.2.4 (a) Static test of steel leaf spring Fig. 2.4 (b) Static test of composite leaf spring.

The optimum values for the design variables, constraints and leaf spring weight obtained

through the GA process. The obtained GA results were compared with experimental data.

Results comparison of load, deflection and stresses are shown in Table 2. These optimum

values obtained through the GA is shown in Table 3 and illustrated in Fig. 3 to 7.

Table 2.7 Comparison results of load, deflection and stresses

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The weight of the composite leaf spring can be reduced by 53.5% from 38.8 N to 18.04 N

by applying the GA optimization technique.

Composite mono leaf spring reduces the weight by 85% for E-Glass/Epoxy over

conventional leaf spring. The reduction of 93%weight is achieved by replacing

conventional steel spring with an optimally designed composite mono-leaf spring.

From the results, it is observed that the composite leaf spring is lighter and more

economical than the conventional steel spring with similar design specifications

The study demonstrated that composites can be used for leaf springs for light weight

vehicles and meet the requirements, together with substantial weight savings

As stated by Sardou and Djomseu (2000), there are three ways to introduce composite on

vehicle suspension. The first is to take away a metal leaf spring and put in place a composite leaf

spring. Second is to design a composite axle doing anti roll as well as spring and guidance task.

The last one is to design a metal suspension and to use composite spring only for its vehicle

properties. First and second solutions design the composite to carry a complex job of wheel control

and suspension spring. The task is rather complex for composite and end up with a relatively small

benefit in weight and cost, on top of that suspension quality is relatively poor. However, in the field

of vehicle suspension, the industry looks for a cost effective composite spring with minimum mass

capable of resisting corrosion and possessing a high degree of durability. Therefore, the automobile

industry has shown increased interest in the replacement of steel springs with composite springs

especially glass fibre composites rather than others such as carbon fiber due to the cost factor.

Accourding To Gulur Siddaramanna Shiva Shankar∗, Sambagam Vijayarangan Received

20 June 2005; Accepted 07 April 2006 (19)

The development of a composite mono leaf spring having constant cross sectional area,

here the stress level at any station in the leaf spring is considered constant due to the

parabolic type of the thickness of the spring, has proved to be very effective.

The study demonstrated that composites can be used for leaf springs for light weight

vehicles and meet the requirements, together with substantial weight savings.

The 3-D modeling of both steel and composite leaf spring is done and analysed using

ANSYS.

A comparative study has been made between composite and steel leaf spring with respect

to weight, cost and strength.

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The analytical results were compared with FEA and the results show good agreement

with test results.

From the results, it is observed that the composite leaf spring is lighter and more

economical than the conventional steel spring with similar design specifications.

Adhesively bonded end joints enhance the performance of composite leaf spring for

delamination and stress concentration at the end in compare with bolted joints.

Composite mono leaf spring reduces the weight by 85 % for E-Glass/Epoxy, 91 % for

Graphite/Epoxy, and 90 % for Carbon/Epoxy over conventional leaf spring.

As per M. M. Patunkar & D. R. Dolas “Modelling and Analysis of Composite Leaf Spring under

the Static Load Condition by using FEA” (20)

Under the same static load conditions deflection and stresses of steel leaf spring and

composite leaf spring are found with the great difference. Deflection of Composite leaf

spring is less as compared to steel leaf spring with the same loading condition.

Conventional steel leaf spring was found to weigh 23 Kg. whereas E-Glass/Epoxy mono

leaf spring weighs only 3.59 Kg. Indicating reductions in weight by 84.40% same level of

performance.

Conventional Leaf spring show failure at eye end only. At maximum load condition also

Composite Leaf Spring shows the minimum deflection as compared to Steel Leaf Spring.

Composite leaf spring can be used on smooth roads with very high performance

expectations.

However on rough road conditions due to lower chipping resistance failure from chipping

of composite leaf spring is highly probable.

As per J P Hou, J-Y Cherruault, G Jeronimidis and R Mayer (25) A new design of the double-

leaf spring has been presented in this paper. Static tests show that the springs can carry safely the

specified 150 kN maximum load. The composite double-leaf spring has similar static stiffness’s

to the steel spring that it replaces. A dedicated shaker rig has been used to collect valuable

information on the dynamic response of the real system under various load conditions. Results

have shown that the system at tare load needs more damping to ensure a smoother ride. Finite

element predictions of stiffness, strain, and dynamic responses of the spring agree well with the

experimental results. This gives confidence in the use of finite element method for the design of

composite springs and for performance predictions. Results from FEA also show that the bottom

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leaf can maintain the gross vehicle mass in the case where the top leaf fails by delimitation. This

mode of failure is a safe one, as the eye end remains intact. Investigation of composite leaf

spring in the early failed to yield the production facility because of inconsistent fatigue

performance and absence of strong need for mass reduction. Researches in the area of

automobile components have been receiving considerable attention now. Particularly the

automobile manufacturers and parts makers have been attempting to reduce the weight of the

vehicles in recent years. Emphasis of vehicles weight reduction in 1978 justified taking a new

look at composite springs. The development of a lite flex suspension leaf spring is first achieved.

Based on consideration of chipping resistance base part resistance and fatigue resistance, a

carbon glass fiber hybrid laminated spring is constructed. A general discussion on analysis and

design of constant width, variable thickness, and composite leaf spring is presented. Recent

developments have been achieved in the field of materials improvement and quality assured for

composite leaf springs based on microstructure mechanism. All these literature report that the

cost of composite; leaf spring is higher than that of steel leaf spring. Hence an attempt has been

made to fabricate the composite leaf spring with the same cost as that of steel leaf spring.

Material properties and design of composite structures are reported in many literatures.

Very little information are available in connection with finite element analysis of leaf spring in

the literature, than too in 2D analysis of leaf spring. At the same time, the literature available

regarding experimental stress analysis more. The experimental procedures are described in

national and international standards. Recent emphasis on mass reduction and developments in

materials synthesis and processing technology has led to proven production vehicle equipment.

A lot of research has been done on natural fiber reinforced polymer composites but

research on coconut based polymer composites is very rare. Against this background, the present

research work has been undertaken, with an objective to explore the potential of coconut fiber

polymer composites and to study the mechanical and wear characterization of different

composites.

2.1 Objectives of the Present Work

The objectives of the project are outlined below.

Fabrication of glass fibre reinforced epoxy resin based hybrid composite with filler

content. Where we change the percentage of glass fiber.

Evaluation of mechanical properties (tensile strength, flexural, hardness,

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impact strength etc.)

The present work is to design, fabricate and experimental testing and analysis of

composite spring made up of E-glass fiber, epoxy resin & Hardner with constant width

and thickness throughout its length.

CHAPTER-3

. MATERIALS AND METHODS

3.1. Introduction

This chapter describes the details of processing of the composites and the experimental

procedures followed for their characterization and process evaluation. The raw materials used in

this work are

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1. E-glass Fiber

2. Dubeckot 520F Epoxy resin

3. Resin hardener

3.2 Material selection

Materials constitute nearly 60%-70% of the vehicle cost and contribute to the quality and

the performance of the vehicle. Even a small amount in weight reduction of the vehicle, may

have a wider economic impact. Composite materials are proved as suitable substitutes for steel in

connection with weight reduction of the vehicle. Hence, the composite material have been

selected for leaf spring design.

3.2.1 Fibres Selection

The commonly used fibers are carbon, glass, keviar, etc.. Among these, the glass fiber

has been selected based on the cost factor and strength. The types of glass fibers are C-glass,S-

glass and E-glass. The C-glass fiber is designed to give improved surface finish.S-glass fiber is

design to give very high modular, which is used particularly in aeronautic industries. The E-glass

fiber is a high quality glass, which is used as standard reinforcement fiber for all the present

systems well complying with mechanical property requirements. Thus, E-glass fiber was found

appropriate for this application.

3.2.2 Resins Selection

In a FRP leaf spring , the inter laminar shear strengths is controlled by the matrix system

used . since these are reinforcement fibers in the thickness direction , fiber do not influence inter

laminar shear strength. Therefore, the matrix system should have good inter laminar shear

strength characteristics compatibility to the selected reinforcement fiber. Many thermo set resins

such as polyester, vinyl ester, azpoxy resin are being used for fiber reinforcement plastics(FRP)

fabrication . Among these resin systems, epoxies show better inter laminar shear strength and

good mechanical properties. Hence, epoxide is found to be the best resins that would suit this

application. different grades of epoxy resins and hardener combinations are classifieds , based on

the mechanical properties.

Among these grades , the grade of epoxy resin selected is Dobeckot 520 F and the grade of

hardener used for this application is 758. Dobeckot 520 F is a solvent less epoxy resin.

Which in combination with hardener 758 cures into hard resin . Hardener 758 is a low viscosity

polyamine. Dobeckot 520 F , hardener 758 combination is characterized by

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Good mechanical and electrical properties

Faster curing at room temperature

Good chemical resistance properties

3.3 PROPERTIES OF E-GLASS / EPOXY COMPOSITE

By considering the property variation in the tapered system improper bonding and

improper curing, etc. some constant of property value are reduced from calculated values using

equations. The material properties for E-glass / Epoxy composite for 60% of fiber volume is

given below: -

3.3.1 PROPERTIES VALUES

Tensile modulus along X direction (Ex),MPa 14000

Tensile modulus along Y direction (Ey),MPa 6030

Tensile modulus along Z direction (Ez),MPa 1530

Tensile strength of the material,MPa 800

Compressive strength of the material,MPa 450

Shear modulus along XY direction(Gxy),MPa 2433

Shear modulus along YZ direction(Gyz),MPa 1600

Shear modulus along ZX direction(Gzx),MPa 2433

Flexural modulus of the material,MPa 40000

Flexural strength of the material,MPa 1000

Poisson ratio along XY direction(NUxy) 0.217

Poisson ratio along YZ direction(NUyz) 0.366

Poisson ratio along ZX direction(NUzx) 0.217

3.4 Characterization of the Composites

3.4.1 Density

The theoretical density of composite materials in terms of weight fraction can easily be

obtained as for the following equations given by Agarwal and Broutman [26].

Where, W and ρ represent the weight fraction and density respectively. The suffix f, m and ct

stand for the fiber, matrix and the composite materials respectively. The composites under this

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investigation consists of three components namely matrix, fiber and particulate filler. Hence the

modified form of the expression for the density of the composite can be written as

Where, the suffix „p’ indicates the particulate filler materials. The actual density of the

composite, however, can be determined experimentally by simple water immersion technique.

The volume fraction of voids in the composites is calculated using the following equation:

3.4.2 Micro-hardness measurement

Micro-hardness measurement is done using a Leitz micro-hardness tester. A diamond

indenter, in the form of a right pyramid with a square base and an angle 1360 between opposite

faces, is forced into the material under a load F. The two diagonals X and Y of the indentation

left on the surface of the material after removal of the load are measured and their arithmetic

mean L is calculated. In the present study, the load considered F = 24.54N and Vickers hardness

number is calculated using the following equation.

and

Where F is the applied load (N), L is the diagonal of square impression (mm), X is the horizontal

length (mm) and Y is the vertical length (mm).

3.4.3 Tensile and flexural strength

The tensile test is generally performed on flat specimens. The commonly used specimens

for tensile test are the dog-bone type and the straight side type with 14 end tabs. During the test a

uni-axial load is applied through both the ends of the specimen. The ASTM standard test method

for tensile properties of fiber resin composites has the designation D 3039-76. The length of the

test section should be 200 mm. The tensile test is performed in the universal testing machine

(UTM) Instron 1195 and results are analyzed to calculate the tensile strength of composite

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samples. The short beam shear (SBS) tests are performed on the composite samples at room

temperature to evaluate the value of flexural strength (FS). It is a 3-point bend test, which

generally promotes failure by inter-laminar shear. The SBS test is conducted as per ASTM

standard (D2344- 84) using the same UTM. Span length of 40 mm and the cross head speed of 1

mm/min are maintained. The flexural strength (F.S.) of any composite specimen is determined

using the following equation.

Where, L is the span length of the sample. P is the load applied; b and t are the width and

thickness of the specimen respectively.

3.4.4 Physical and mechanical properties

The theoretical and measured densities of all composite samples along with the

corresponding volume fraction of voids are presented in Table 3. It may be noted that the

composite density values calculated theoretically from weight fractions using Eq. (2) are not in

agreement with the experimentally determined values. The difference is a measure of voids and

pores present in the composites.

3.5 Processing of the Composites

E-glass fibers are reinforced with Dubeckot 520F Epoxy resin, chemically belonging to

the epoxide family is used as the matrix material. Its common name is Bisphenol A Diglycidyl

Ether. The low temperature curing epoxy resin and corresponding hardener are mixed in a ratio

of 10:1 by weight as recommended. The epoxy resin and the hardener are supplied by Ciba

Geigy India Ltd. E-glass fiber and epoxy resin has modulus of 72.5 GPa and 3.42GPa

respectively and possess density of 2590 kg/m3 and 1100kg/m3 respectively. weight fraction of

glass fiber in the composite) is kept at 50% for all the samples. The castings are put under load

for about 24 hours for proper curing at room temperature. Specimens of suitable dimension are

cut using a diamond cutter for physical characterization and other test.

The material used as coarsely woven E-glass fiber having density 400 gsm. and Glass

fiber chopped stand mat (175-450 gsm) which gives maximum tensile strength, toughness and

low cost. The resin selection was main factor because it influences the economy of leaf spring

for reducing prize,. The resin used as Dobeckot 520 F. The hardener 758 is used with this resin.

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(general purpose resin) the prepared matrix it consist of 10:1 mass ratio the mass ratio of resin to

hardener to fiber were calculated for each weight percentage composite based on size of mold,

desired thickness of composite and density of fiber and epoxy. Each. % wt prepared in separate

jar. In order to facilitate wetting of fibers and epoxy resin with pot life of 2 h is selected.

3.4 Composite fabrication

Preparation of mould:- Material used as Plywood. The mold was fabricated as per

desired dimension. Arc length = 1160mm. length of mould= 1010mm, width= 45mm, arc height

at axle=120 mm. The constant cross section design which ensures the fiber pass continuously

without interruption along length direction, which is advantageous to fiber reinforced structure.

The glass fiber were cut to desired length, so that they can be deposited on mold layer- by layer

during fabrication of composite leaf spring. Apply the wax/gel.. Prepare the solution of resin &

Place the first layer of glass fiber chopped mat on mould followed by epoxy resin solution over

mat. Wait for 5-10 min. Repeat the procedure till the desired thickness was obtained. The

duration of the process may take up to 25- 30 min. And finally remove the leaf spring from

mould.

Fig. 3.1: Prepared specimen of composite leaf spring Fig. 3.2: Graph Load vs Deflection

Testing of composite & steel leaf spring are takes place on UTM .

Various specification of UTM are as follows:- Make:- Heico New Delhi Model No.:- HL 9C:10

Capacity:- 20 ton Least weight- 10 kg. Maximum weight- 5 ton Dial gauge least count:-0.01mm

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22


CHAPTER-4

EXPERIMENTAL METHODOLOGY

4.1 EXPERIMENTAL SETUP -

Move the plunger up to desired height so that we can fix the fixture and leaf spring for

test. Fix the position of fixture. On the fixture place the specimen. Set the universal testing

machine. Apply the loads in steps of 20 kg gradually. Note down the deflection readings.

Table-4.1 Deflection between composite and steel leaf spring

Leaf Spring Experimental Analytical [FEA]

STEEL 94 89.17 -

COMPOSITE 95 104.85 96.962

4.4 Stress analysis by using Ansys 10.0 Software

The element SHELL 99, SOLID 46 are the best suited for modeling of composite material.

SHELL 99 is an 8 – node, 3D shell element with six degree of freedom at each node. The

advantage of SOLID 46 is that we can stack several elements to model more than 250 layers.

Here selected element was SOLID 46.

Table 4.2 Stress analysis of composite and steel leaf spring

Leaf Spring Experimental Analytical [FEA]

STEEL 220.18 220.18 -

COMPOSITE 220.18 220.18 247.172

4.5 Performing a Static Analysis

The procedure for a static analysis consists of these tasks:

1. Build the Model

2. Define Parameters

The parameters for building the composite leaf spring are as follows-

Young's modulus is 11.9 GPa (EXX) value is 11900 MPa, Poison ratio is 0.217 XY(PRXY)

value is 0.217

Length of cantilever beam =505mm, Width of cantilever beam.= 45mm, Height of cantilever

beam. = 30mm

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3. Stacking Sequence of Layers.

The stacking sequence of layer are shown fig having unidirectional fibre with stacking angle of

zero.

Table.4.3 Weight Comparison

Leaf Sprig Type Steel Composite

Weight 13.4 (with eye) 2.365 (without eye)

Fig. 4.1: Finite element model of composite leaf spring. Fig. 4.2: Mesh model of composite leaf spring

Fig. 4.3: Stacking sequences of layers. Fig. 4.4: Mesh model with application of load

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Fig. 4.5: Deflection along y-direction Fig. 4.6: Deflection along x-direction

Fig. 4.7: Deflection along z-direction Fig. 4.8: Stresses along x-direction

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CHAPTER-5

Result & Discussion

5.1 Background

Result & Discussion

The performance of existing steel leaf spring was compared with the fabricated

composite leaf spring. Testing has been done for unidirectional E-Glass/Epoxy mono composite

leaf spring. Since the composite leaf spring is able to withstand the static load, it is concluded

that there is no objection from strength point of view also, in the process of replacing the

conventional leaf spring by composite leaf spring. Since, the composite spring is designed for

same stiffness as that of steel leaf spring, both the springs are considered to be almost equal in

vehicle stability. The major disadvantages of composite leaf spring are sometimes breaking of

fibers. When composite leaf spring hit by stone then there is chances of breaking of fibers. This

may result in a loss of capability to flexural stiffness. But this depends on the condition of the

road. In normal road condition, this type of problem will not occur.

5.10 Summary:-

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CHAPTER 6

CONCLUSIONS

This analytical and experimental investigation into the erosion behavior of E glass-epoxy

Resin hybrid composites leads to the following conclusions:

1. This work shows that successful fabrication of a glass fiber reinforced epoxy composites

with and without filler by simple hand lay-up technique.

2. These composites using Filler have adequate potential for tribological and Automobile

applications.

1. The composite leaf spring is designed according to constant cross-section area method.

2. The 3-D model of the composite leaf spring is analyzed using Ansys 10.0 Software.

3. Static test has been conducted to predict the stress and displacement at different locations

for various load value.

4. The results of the Analysis by ansys software are verified with the test results.

5. A comparative study has been made between composite and steel leaf springs with

respect to weight, riding quality, cost and strength.

6.1. Scope for Future Work

1. This study leaves wide scope for future investigations. It can be extended to newer

composites using other reinforcing phases and the resulting experimental findings can be

similarly analyzed.

2. Stress evaluation of E glass fiber reinforced epoxy resin composite has been a much less

studied area. There is a very wide scope for future scholars to explore this area of

research. Many other aspects of this problem like effect of fiber orientation, loading

pattern, weight fraction of ceramic fillers on wear response of such composites require

further investigation.

27


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mailto:[email protected]


APPENDIX – A

30

Final Report

Documents

appl poly

generated

minimum mass

conventional

universal

steel leaf

substantial

composite