Composite Project b Tech[1]

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Performance of natural @ synthetic fibers reinforced epoxy composites

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CHAPTER-1

INTRODUCTION

1.1 Definition of composite material

Materials consisting of two or more distinct phases brought together, with a

recognizable definite interface, the constituent materials insoluble i.e. physically

separable resulting with the properties which are uniquely different compared to the

constituent materials showing synergism the presence of one material will make the other

to behave differently.

Two or more different constituent materials are together intimately mixing them

by various means which are acting together and performing together to yield enhance

property and quality superior to what is promised.

A substance consisting of two or more materials, insoluble in one another which,

are combined to form a useful engineering material processing certain properties not

possessed by the constituents. Something combining the typical or essential

characteristic of individuals making up a group.

1.2 Theory of composites

Composites are considered to be any multi-phased material that exhibits

significant properties of the properties of constituent phase. These are artificially made as

that of naturally occurs. These are used to produce extraordinary materials (ceramics,

polymers, and various materials.

This combination of materials to form a new material system with enhanced

material properties is well documented in history. For example, the Japanese warriors

were known to use laminated metals in the forging of their swords to obtain desirable

material properties. More recently, in the 20th century civil engineers placed steel rebar in

cement and aggregate to make a well-known composite material, i.e. reinforced concrete.

Their advantages over other materials for high-performance, lightweight

applications have attracted many industries such as aerospace, automobile, infrastructure,

sports and marine to explore and increase their usage.


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1.3 The criteria to be met in composite material

1) The composite material must be man-made i.e. it should be manufactured one.

2) The composite material must be a combination or two or more physically and/or

chemical distinct materials with a distinct interface separable.

3) The composite materials must have the characteristic properties, which would not be

achieved by any of the constituent components acting alone, which have different

properties.

4) The constituents forming the composite must be intimately mixed or dispersed and

made as a homogeneous content.

5) Both constituents have to be present in reasonable proportions (at least>55%).

In general, for composites the following factors are very important.

1) Position and location of reinforcement.

2) Aspect ratio of the reinforcement (shape and dimensions).

3) Bonding has to be ensured between constituent materials.

1.4 The need of composite materials

1.The demand made by diverse field as space, aeronautics, civil construction and

automobiles, on materials to be forever better overall performance by one as single

material.

2. Due to the continuing quest for improved performance, by various criteria including

less weight more strength i.e. high strength to weight ratio and lower cost. For the

advantages of

a) Flexible design (for optimum design by providing fluidity to design).

b) Energy consciousness.

c) Extending the limit of usefulness.

3. To achieve enhanced property (or) to give the quality of product superior to that what

is promised.

Example of composites

1. Mud reinforced with straw (brick)


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2. Mixture of stones, sand and cement (concrete)

3. Bamboo reapers and lake bed clay

1.5 Classification of composites

1.5.1 Fibrous composites

Fibrous composites consist of fibers of one material in a matrix of another. it may

be continuous or discontinuous fibers.

Example: Glass-epoxy

Glass-polyester

Kevlar-epoxy

Continuous & Discontinuous & Discontinuous &

Aligned fibers Aligned fibers Randomly

Aligned fibers

Figure 1: Fibrous composites


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1.5.2 Particulate composites

Particulate composites are composed of macro-sized particles of one material in a

matrix of another, either metallic or non-metallic.

Examples: Sinter aluminum powder

Ceramic-composites (cermets)

Figure 2: Particulate composites

1.5.3 Laminated composites

Laminated composites are made up of different materials, including the

composites of the first two types.

Examples: Laminar composites

Sandwich panels

Figure 3: laminated composites


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1.6 Categorization of composites

Composites can be categorized by matrix characteristics, including

1. Type

a. Metal

b. Ceramic

c. Polymeric

d. Rubber

2. Ceramic nature

a. Organic

b. Inorganic

3. Origin

a. Natural

b. Artificial4. Process ability

a. Thermo set

b. Thermoplastic

Composites can be categorized by their fiber characteristics, including

1. Type

a. Glass

b. Carbon (graphite)

c. Kevlar (aramid)

2. Fiber posting (or) Alignment

a. Random

b. Unidirectional

c. Bi-directional (woven)


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1.6.1 Advanced composites

There are five principal types of advanced composites material in wide use.

The composite types, which includes polymer matrix composites (PMC), metal

matrix composites (MMC), ceramic matrix composites (CMC), carbon-carbon (CC) and

hybrid composites.

1.7 Hybrid composite materials

1.7.1 Definition

Composites containing more than one type of fiber are commonly known as

hybrid composites. The term hybrid is generally used to denote the incorporation of two

different types of material into one single material. And the level of mixing can be either

on a small scale (fiber, tows) or on a large scale (layers, pultrusions, ribs).

The purpose of hybridization is to construct a new material that will retain the

advantages of its constituents but not their disadvantages. However, for most properties,

the rule of mixtures (i.e. the weighted sum of the constituents properties according to the

composition) is only an upper bound. For example, in the case of tensile strength, the

stiffer material fails first at roughly its normal failure strain and therefore the hybrid is

weaker than both its constituents.

However, there are other factors such as cost, weight, post-failure behavior and

fatigue performance that sometimes lead the designer to the use of hybridization in order

to the exact needs of the structure under design.


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1.7.2 Types of hybrids

There are several types of hybrid composites, characterized according to the way

in which the constituent materials are mixed.

1. Sandwich hybrids, also known as core-shell, in which one material is sandwiched

between two layers of another.

2. Intraply, or laminated, where alternate layers of the two (or more) materials are

stacked in a regular manner.

3. Itraply, or tow-to-tow, in which alternative layers of the two (or more) constituent

types of fiber are mixed in a regular or random manner.

4. Intimately mixed hybrids, where the constituent fibers are made to mix as

randomly as possible so that no concentrations of either type are present in the

material. And other kinds such as those reinforced with ribs, pultruded wires,

thin veils of fiber and combinations of the above.

1.7.3 Benefits of hybridization

1. Balance the cost with weight and performance.

2. Enhanced strain to failure as compared to pure single fiber.

3. Enhanced energy absorption to failure and hence fails gradually.

4. Improved fatigue strength.

5. Flexural strength can be improved.

6. Improved impact strength.

1.8 Advantages of composite materials

1) Light in weight.

2) High strength to weight ratio.

3) Low density.

4) Excellent directional strength.

5) Good weather resistance.

6) Greater fatigue resistance than steel or aluminum.

7) Greater design flexibility than homogeneous materials.


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8) Potential for corrosion is significantly reduced.

9) Minimize part count.

10)Good electric insulation.

11)Low sound transmission.

12)Low thermal conductivity and low thermal coefficient of thermal expansion.

13)Radar transparency.

14)Non-magnetic.

1.9 Applications of composite materials

Some of the applications of composite materials in industries are as listed in the

table.

Industry Successful application

Transportation Passenger car, highway tractors, truck body, trailers,

recreation vehicles, floor for rail cars, etc.

Aircraft industry Fuselage, wing, rotor blades, cargo pods, engine cowls,

boosters, satellites, helicopters, high strength turbine blades.Marine Pleasure boats, workboats, commercial vessels, hovercraft,

hydrofoils, and submarines.

Building House roofs, modern structures, and tanks.

Chemical Piping, ducts, hood stacks and storage tank.

Appliances and

Equipment

Tanks, air condition frames, condenser fans, valves, chasses,

containers and other components.

Electrical Electrical contacts, electrodes, low expansion pcb in lamps.Sports Tennis racquets, golf club shafts, fishing rods, snow skis

water skis, hokey sticks and arrows.

Medicine Artificial limbs, dentures, etc.

Table 1: General applications of composite material


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Apart from these specific applications, the use of fiber reinforced plastics

(FRP) composite material is also being explored in automobile industry, sports

industry, windmills etc. most of the demand of modern society, which normally

require material having high strength and stiffness at reduced weights and cost are

being satisfied by composite materials.

Applications of composite in aerospace

Sl.No Aircraft Principal components

1 Air bus a-300 Rudder, outboard spoiler, vertical fin,

cabin vertical support rods, main landing

gear fairing.

2 Boeing 737 Horizontal stabilizer.

3 Boeing 747 Outboard aileron engine inlet and outlet

cowl, floor panels.

4 Mirage 2000 Fin equipped with radar, front landingdoor, and access and inspection doors.

5 light combat aircraft (LCA)

India

Rudder, vertical fin, wings.

6 NALS light aircraft HANSA

(India)

Complete airframe structure (gfrp-foam

sandwich).

7 NALS 14 seated light aircraft

SARAS (India)

Composites of flight control systems of

rudder, elevator, flifs, etc.

Table 2: Applications of composite material in aircrafts


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CHAPTER -2

REVIEW OF LITERATURE

2.1 Different forms of reinforcement

1) Strands: a collection of filaments, the basic from in which fiber is produced.

2) Yarns: twisting the strands makes yarns.

3) Roving: the collection of strands made in tape like form without twisting.

4) Unidirectional cloth: roving is aligned in warp, a mat from with minimum wet

fiber.

5) Woven roving mat: roving is woven with fiber in warp and weft directions.

6) Continuous strand mat: strands are randomly oriented and bonded to other with

a binder.

2.2 Different structures of woven fabrics

A fabric is material constructed of inter laced yarns, fibers or filament and is

usually planer in structure. Interlacing individually are filaments, ends, yarns and

rowing makes a woven reinforced fabric. Woven reinforcements consist of orthogonal

fiber. The long direction of the fibers is called the warp while the width direction of the

fiber is called the fill, weft or woof. Fills are also called picks. The weave of the fabric

refers how to warp yarn and weft yarn are inter laced.

The fabric composites have low fiber to volume ratio, which contributes to the

low elastic moduli and strength properties. The major fabric types are twill weave, stain

weave, leno weave, plain weave, and triaxial weaves.


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2.2.1 Plain weaves

Figure 4: Plain weaves

The plain weave is the oldest and most common textile weaves. One warp end is

repeatedly woven over one fill yarn and under the next. Plain weave being the most inter

laced is the firmest. The most stable construction providing porosity and minimum

slippage. The strength is uniform in both directions and is most resistant to in plane shear

movement. Though very stable, plain weave are relatively in efficient and have poor drag

i.e., they do not conform easily to surface to double curvatures.

2.2.2 Twill weaves

Figure 5: Twill weaves

Twill weaves are one or more warp ends passing over and fewer than two, three or

more fill pieces in regular pattern. These fabrics have characteristics diagonal patterns

known as twill lines. Twill weaves are relatively stable and structurally efficient than

plain weaves and have relatively good drape.

2.2.3 Stain weaves

Figure 6: Stain weaves
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http://www.finemeshmetals.co.uk/images/Plain_Weave.JPG&imgrefurl=http://www.finemeshmetals.co.uk/wovenwire.htm&usg=__RHO8KEZ17i-V1T0XUTumWKX0ABs=&h=648&w=687&sz=90&hl=en&start=1&um=1&tbnid=wEIWpihgO-7EaM:&tbnh=131&tbnw=139&prev=/images?q=plain+weave&um=1&hl=en&sa=Xhttp://images.google.co.in/imgres?imgurl=http://www.tech.plym.ac.uk/sme/mats324/Figures/C2%20plainweave.jpg&imgrefurl=http://www.tech.plym.ac.uk/sme/MATS324/MATS324C2%20fabrics.htm&usg=__9ZoH5EXNoKlbDG4ZoDktDLtko0o=&h=588&w=569&sz=203&hl=en&start=2&um=1&tbnid=NiwScPHzX46LIM:&tbnh=135&tbnw=131&prev=/images?q=plain+weave&um=1&hl=en&sa=Xhttp://images.google.co.in/imgres?imgurl=http://www.textum.com/images/leno.gif&imgrefurl=http://www.textum.com/weaves/&usg=__bi6PCHA0Qa5RjqPZ-x4FcZ8fOao=&h=123&w=125&sz=4&hl=en&start=5&tbnid=ZdJUclbKJKJCyM:&tbnh=89&tbnw=90&prev=/images?q=leno+weave&hl=enhttp://images.google.co.in/imgres?imgurl=http://www.fabrics.net/colpics/1001/photo3.jpg&imgrefurl=http://www.fabrics.net/joan1101.asp&usg=__sb8eOsrvqd61jtFkvSMF8E5pWg0=&h=220&w=210&sz=39&hl=en&start=2&tbnid=FGGzSWi0iw5FkM:&tbnh=107&tbnw=102&prev=/images?q=leno+weave&hl=enhttp://www.google.co.in/imgres?imgurl=http://www.lockergroup.com/images/content/buyguide/FIG2-TwillWeave.jpg&imgrefurl=http://www.lockergroup.com/buyersguide/&h=224&w=200&sz=15&tbnid=e1tSQBkUKP0Z8M::&tbnh=108&tbnw=96&prev=/images?q=twill+weave&hl=en&usg=__XvXfmMc-Gx7NLAiJ2VhRe0pdV0c=&ei=NVSiSce_LJDG6gOMmICtCg&sa=X&oi=image_result&resnum=2&ct=image&cd=1http://www.google.co.in/imgres?imgurl=http://www.finemeshmetals.co.uk/images/Twill_Weave.JPG&imgrefurl=http://www.finemeshmetals.co.uk/wovenwire.htm&h=648&w=687&sz=80&tbnid=T2uiOwd631k0cM::&tbnh=131&tbnw=139&prev=/images?q=twill+weave&hl=en&usg=__0E6PbtKofZwA0rJPPNQ8lX-PIJA=&ei=AFGiSaiFMMzPkAWOsaXJCw&sa=X&oi=image_result&resnum=1&ct=image&cd=1http://images.google.co.in/imgres?imgurl=http://www.finemeshmetals.co.uk/images/Plain_Weave.JPG&imgrefurl=http://www.finemeshmetals.co.uk/wovenwire.htm&usg=__RHO8KEZ17i-V1T0XUTumWKX0ABs=&h=648&w=687&sz=90&hl=en&start=1&um=1&tbnid=wEIWpihgO-7EaM:&tbnh=131&tbnw=139&prev=/images?q=plain+weave&um=1&hl=en&sa=Xhttp://images.google.co.in/imgres?imgurl=http://www.tech.plym.ac.uk/sme/mats324/Figures/C2%20plainweave.jpg&imgrefurl=http://www.tech.plym.ac.uk/sme/MATS324/MATS324C2%20fabrics.htm&usg=__9ZoH5EXNoKlbDG4ZoDktDLtko0o=&h=588&w=569&sz=203&hl=en&start=2&um=1&tbnid=NiwScPHzX46LIM:&tbnh=135&tbnw=131&prev=/images?q=plain+weave&um=1&hl=en&sa=Xhttp://images.google.co.in/imgres?imgurl=http://www.textum.com/images/leno.gif&imgrefurl=http://www.textum.com/weaves/&usg=__bi6PCHA0Qa5RjqPZ-x4FcZ8fOao=&h=123&w=125&sz=4&hl=en&start=5&tbnid=ZdJUclbKJKJCyM:&tbnh=89&tbnw=90&prev=/images?q=leno+weave&hl=enhttp://images.google.co.in/imgres?imgurl=http://www.fabrics.net/colpics/1001/photo3.jpg&imgrefurl=http://www.fabrics.net/joan1101.asp&usg=__sb8eOsrvqd61jtFkvSMF8E5pWg0=&h=220&w=210&sz=39&hl=en&start=2&tbnid=FGGzSWi0iw5FkM:&tbnh=107&tbnw=102&prev=/images?q=leno+weave&hl=enhttp://www.google.co.in/imgres?imgurl=http://www.lockergroup.com/images/content/buyguide/FIG2-TwillWeave.jpg&imgrefurl=http://www.lockergroup.com/buyersguide/&h=224&w=200&sz=15&tbnid=e1tSQBkUKP0Z8M::&tbnh=108&tbnw=96&prev=/images?q=twill+weave&hl=en&usg=__XvXfmMc-Gx7NLAiJ2VhRe0pdV0c=&ei=NVSiSce_LJDG6gOMmICtCg&sa=X&oi=image_result&resnum=2&ct=image&cd=1http://www.google.co.in/imgres?imgurl=http://www.finemeshmetals.co.uk/images/Twill_Weave.JPG&imgrefurl=http://www.finemeshmetals.co.uk/wovenwire.htm&h=648&w=687&sz=80&tbnid=T2uiOwd631k0cM::&tbnh=131&tbnw=139&prev=/images?q=twill+weave&hl=en&usg=__0E6PbtKofZwA0rJPPNQ8lX-PIJA=&ei=AFGiSaiFMMzPkAWOsaXJCw&sa=X&oi=image_result&resnum=1&ct=image&cd=1http://images.google.co.in/imgres?imgurl=http://www.finemeshmetals.co.uk/images/Plain_Weave.JPG&imgrefurl=http://www.finemeshmetals.co.uk/wovenwire.htm&usg=__RHO8KEZ17i-V1T0XUTumWKX0ABs=&h=648&w=687&sz=90&hl=en&start=1&um=1&tbnid=wEIWpihgO-7EaM:&tbnh=131&tbnw=139&prev=/images?q=plain+weave&um=1&hl=en&sa=Xhttp://images.google.co.in/imgres?imgurl=http://www.tech.plym.ac.uk/sme/mats324/Figures/C2%20plainweave.jpg&imgrefurl=http://www.tech.plym.ac.uk/sme/MATS324/MATS324C2%20fabrics.htm&usg=__9ZoH5EXNoKlbDG4ZoDktDLtko0o=&h=588&w=569&sz=203&hl=en&start=2&um=1&tbnid=NiwScPHzX46LIM:&tbnh=135&tbnw=131&prev=/images?q=plain+weave&um=1&hl=en&sa=Xhttp://images.google.co.in/imgres?imgurl=http://www.textum.com/images/leno.gif&imgrefurl=http://www.textum.com/weaves/&usg=__bi6PCHA0Qa5RjqPZ-x4FcZ8fOao=&h=123&w=125&sz=4&hl=en&start=5&tbnid=ZdJUclbKJKJCyM:&tbnh=89&tbnw=90&prev=/images?q=leno+weave&hl=enhttp://images.google.co.in/imgres?imgurl=http://www.fabrics.net/colpics/1001/photo3.jpg&imgrefurl=http://www.fabrics.net/joan1101.asp&usg=__sb8eOsrvqd61jtFkvSMF8E5pWg0=&h=220&w=210&sz=39&hl=en&start=2&tbnid=FGGzSWi0iw5FkM:&tbnh=107&tbnw=102&prev=/images?q=leno+weave&hl=enhttp://www.google.co.in/imgres?imgurl=http://www.lockergroup.com/images/content/buyguide/FIG2-TwillWeave.jpg&imgrefurl=http://www.lockergro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Page No 12

The stain weave represents a family of constructions with a minimum of inter

lacing. In these the weft yarns are periodically skip or float over several warp yarns. Stain

weaves can be produced as standard of 4.5 or 8 harness forms. The stain weave is more

reliable than the plain weave as the floating yarns that are not woven in fabric creating a

considerable suppleness and looseness. It conforms readily to compound curves can be

woven into a very high density. This is because the weave produces a construction with

low resistant shear distortion. This is one reason why stain weaves are preferred for many

aerospace applications. But as the number of harness increases, so the float lengths and

degree of looseness and sleaziness making the fabric more difficult to control during

handling operations.

2.2.4 Leno weaves

Figure 7: Leno weaves

To have an advantage over the very light fabrics that tend to sleazy the leno weave

fabrics are introduced .in this type of construction, two or more wrap yarns cross over

each other, locking fill place .the leno weaves help to prevent the un reviling during

handling operations but is unsteadily for obtaining good laminate physical properties.

2.2.5 Tri axial weaves

Figure 8: Tri axial weaves

A few fabrics with non-orthogonal fiber orientation have been developed. One of

them is tri axial weave is called do weave .so the pattern consists of weave of weave in
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a fashion with a straight yarn in between them. The major disadvantages of these

constructions are that does not have stableness and tear resisting.

2.3 Fiber reinforcement

Different types of reinforced fibers are

1) Glass fibers

2) Carbon fibers

3) Kevlar fibers

4) Boron fibers

2.4 Glass fibers

Fiber of a base material such as glass is muchstiffer and stronger thana bulk glass

itself. This is because crystal in a fiber are aligned along the axis and have only very few

internal defects such as cracks in the material. Fibers and drawing through a small die.

Glass fibers are supplied in the form of slightly twisted yarns consisting of groups of

parallel strands of fibers.

2.4.1 Properties

1) Superior tensile strength.

2) Perfect elasticity.

3) Attractive thermal properties.

4) Excellent moisture resistance.

5) Outstanding dimensional stability.

6) Excellent corrosion resistance.

7) Excellent electrical characteristics.

8) Low cost.


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2.5 Different types of glass fiber

2.5.1 E-glass (E-electrical)

This is a lime-alumina borosilicate glass designed for electricity application. it has

high bulk and surface electrical resistivity. It has a near eutectic composition of si, al 2o3

and cao system e-glass developed to have,

1) High bulk electrical resistivity.

2) High surface resistivity.

3) Good fiber forming characteristics.

Pyrex composition glass, has good electrical properties and suitable for general

application when a combination of good strength and chemical resistance is required.

Over 90% of fibreglasses used for reinforcement are e-glass type. This glass bonds well

to most polymeric resins after an appropriate coupling agent is employed.

2.5.1.1 General properties of E-glass

1) Density =2.540.03gm/cm3.2) Is very important is any glass working process and this is true in fiber drawing.

3) The temperature, at which the viscosity of glass fiber is 10 4.5 poise, is

determined from rate of elongation of stressed fiber. at the strain point for e-glass

is 507c.

4) Annealing point is around 657 c.

5) Youngs modulus e=10.5*10 6 psi.

6) Good tensile strength and melting history.

2.5.2 A-glass

It consists of soda-lime high alkali contents susceptible to moisture. it has limited

use

2.5.3 C-glass

This has better corrosion resistance to acids than e-glass.


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2.5.4 S-glass

It has higher tensile strength and modulus of elasticity than e-glass. It has got

superior strength, retention at elevated temperature and high fatigue limit (high cost).

2.5.5 D-glass

Low dielectric constant and is suited for high performance electronic applications.

2.6 Natural fibers in composites

With the rise of composite materials there is a renewed interest for natural fibers.

Their moderate mechanical properties prevent the fibers from using them in high-

performance applications, but for many reasons they can complete with glass fibers.

Natural fiber composites enjoy excellent potential as wood substitutes in building

industry in view of their low cost, easy availability, saving in energy and pollution free

production. Natural fibers, as a substitute for glass fibers in composite components, have

gained renewed interest the last decade, especially in automotive industries. Fibers like

flax, hemp or jute are cheap, have better stiffness per unit weight and have a lower impact

on the environment.

2.6.1 Advantages

1) Low specific weight, which results in a higher specific strength and stiffness than

glass. This is a benefit especially in parts designed for bending stiffness.

2) It is a renewable resource, the production requires little energy, and co 2 is given back

to the environment.

3) Producible with low investment at low cost, which makes the material an interesting

product for low-wage countries.

4) Friendly processing, no wear of tooling. Better working conditions, no skin irritation.

5) Thermal recycling is possible, where glass causes problems in combustion furnaces.

6) Good thermal and acoustic insulating properties.


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2.6.2 Disadvantages

1) Lower strength properties, particularly its impact strength.

2) Variable quality, depending on unpredictable influences such as weather.

3) Moisture absorption, which causes swelling of the fibers.

4) Limited maximum processing temperature.

5) Lower durability, fiber treatments can improve this considerably.

6) Poor fire resistance.

7) Price can fluctuate by harvest results or agricultural politics.

8) Irregular fiber lengths; spinning is required to obtain continuous yarns.

2.7 Jute as a fiber material

Jute is a lingo-cellolosic best fiber obtained from the bark of two cultivated

species of the genus corchorus capsular is and of the family tiliaceae.jute is cultivated in

the alluvial plains in the tropical and sub-tropical zones of south Asian region jute textiles

are mainly used as packing materials because of their low cost, high strength and

stiffness. Jute has the advantage of being both renewable by agro-effects and environment

friendly due to bio-degradability. Non-traditional applications envisaged for jute include

decorative and furnishing fabrics, floor coverings woven and non-woven geo thermal and

sound insulation media and reinforced plastics and composites.

Although the tensile strength and youngs modulus of jute are lower than those of

glass fibers, the specific modulus of jute fiber is superior to that of glass and on a

modulus per cost basis, jute is for superior. The specific strength per unit cost of jute, too,

approaches that of glass. Therefore, where high strength is not a priority, jute may be used

to fully or new partially replace glass fiber without entailing the introduction of new

techniques of composite fabrication.

The need for using jute fibers in place of the traditional glass fiber partly or fully

as reinforcing agents in composites stems from its lower specific gravity (1.29) and

higher specific modulus (40 Gpa) of jute compared with those of glass (2.5&30 Gpa


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respectively). Apart from much lower cost and renewable nature of jute, much lower

energy requirement for the production of jute (only 2 per cent of that for glass) makes it

attractive as a reinforcing fiber in composites.

The jute composites may be used in everyday applications such as lampshades,

suitcases, paperweights, helmets, shower and bath units. They are also used for covers of

electrical applications, pipes, post boxes, roof tiles, grain storage silos, panels for partition

& false ceilings, bio-gas containers, and in the construction of low cost, mobile or

prefabricated buildings which can be used in times of natural calamities such as floods,

cyclones, earthquakes, etc.

2.7.1 Properties of jute

1) Jute is very stiff fiber with very low extensibility.

2) Its co lour ranges from golden brown to dirty grey depending upon the quality of

the fiber.

3) It is lustrous in appearance and generally has a rough feel. Jute fibers contain

variable number of cells along their length. Hence, the value of filament strength

with in a sample varies widely.

4) Jute has a moisture regain value of 11%at 65% humidity. This is because of

presence of hemi-cellulous in jute.

Jute is mildly acidic in nature.

2.7.2 Effect of moisture

A major draw back associated with the application of jute fibers for reinforcementof resin matrices. Due to presence of hydroxyl and other polar groups in various

constituents of jute fiber, the moisture uptake is high (approx. 12.5 percent at 65 percent

relative humidity &20deg c) by dry fiber and 14.6 percent by wet fiber.

All this leads to (i) poor wet ability with resin and (ii) weak interfacial bonding

between jute fiber and the relatively more hydrophobic matrices. Environmental


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performance of such composites is generally poor due to delamination under humid

conditions.

In order to develop composites with better mechanical properties and

environmental performance, it is necessary to impart hydrophobicity to the fibers by

chemical reaction with suitable coupling agents or by coating with appropriates resins.

Following means can do modification of jute and other natural cellulosic fibers;

chemical means, coating with polymeric solutions and graft copolymerization. The

hydroxyl groups of jute are blocked when chemically treated making the fibers more

hydrophobic.

Polymeric coating of jute fiber is highly effective in enhancing the reinforcing

character of jute fiber, giving as high as 20-40 percent improvements in flexural strength

and 40-60 percent improvements in flexural modulus. These modifications improve the

fiber-matrix resin wet ability and lead to improve bonding. Jute can be graft

copolymerized with vinyl monomers. Grafting of polyacrylonitrile (10-25 percent)

imparts 10-30 percent improvements in flexural strength and flexural modulus of the

composites.

2.7.3 Need for pre-treatment

The jute has property to absorb moisture. The moisture so absorbed can be

seriously being detrimental to the bonding of atoms between the polyester resins and

surface of the jute layers. This will lead to decreased strength of the finished laminate.

This is because the matrix has to effectively transfer maximum load onto the fibers.

If there is a premature cracking or failure of matrix material, then the failure of matrix

material, then there will be a failure of the interface mechanism leading to premature

failure of matrix material. The jute layers, which are cut to the required size, are weighed

using an electronic weigh balance.

The temperature of oven is maintained at 80 deg for a period of one hour. After

one hour oven is switched off and the jute layers are taken out and again weighed in


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electronic balance. The new weight is noted down. The difference in initial weight and

new weight gives moisture content present in jute. The % of moisture is calculated using

the relation.

Moisture content =initial weight

final weight/final weight

Thus the moisture % by weight present in jute is determined.


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CHAPTER-3

THERIOTICAL ANALYSIS

3.1 Matrix materials

Polymers are the most used for matrix than metal or ceramics. They are very poor

inductors of heat and electricity and are generally more resistant to ceramicals than

metals. Polymers are giant chain like structures of molecules with conveniently bonded

carbon atom forming the backbone of chain. The process of making large molecules

(polymers) from small ones (monometers) is called polymerization.

3.2 Functions of the matrix phase

1) It binds the fibers together and acts as a medium by which an externally applied

stress is transmitted and distributed to the fibers; only a very small proportion of

an applied load is sustained by the matrix phase.

2) The matrix material should be ductile.

3) The matrix should protect the individual fibers from fiber damage as a result of

mechanical abrasion and chemical corrosion with environment.

4) The matrix separates the fiber layers and by the virtue of its relative softness,

prevents crack propagation from fiber which otherwise may lead to premature

failure of the composite. The adhesive bonding force between the fiber pullout

and adequate bonding is essential for the effective transmittance of stress from

weak matrix to the strong reinforcement.

3.3 Catalyst and Accelerators

Catalysts are materials, which initiate the chemical reaction that cause the resin to

undergo phase transformation from liquid to solid. Accelerator increases the speed of the

catalytic action. The pot life and gel time depends upon the quantity of accelerator and

catalyst taken.

A wide range of catalysts, accelerators, systems are available for use with

polymers resin. The selection of proper catalyst and amount to use for applications


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depends on the resin, the curing temperature, required working or pot life and the gel

time.

The most commonly catalyst is benzoyl peroxide, which is efficient, easy to

handle, readily soluble in monomeric styrene storable for long periods of the time without

the loss of activity and stable at room temperature. Cobalt naphtha late is used as

accelerator.

3.4 Resin systems

Any resin system for use in a composite material will require the following

properties

1) Good mechanical properties.

2) Good adhesive properties.

3) Good toughness properties.

4) Good resistance to environmental degradation.

3.4.1 Mechanical properties of the resin system

Figure 9: Stress-strain curve for an ideal resin system

The figure below shows the stress / strain curve for an ideal resin system.

The curve for this resin shows high ultimatestrength, high stiffness and a high strain

to failure. This means that the resin is initially stiff but at the same time will not suffer

from brittle failure.


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It should also be noted that when a composite is loaded in tension, for the full

mechanical properties of the fiber component to be achieved, the resin must be able to

deform to at least the same extent as the fiber. The figure below gives the strain to

failure for e-glass, s-glass, aramid and high-strength grade carbon fibers on their own.

Here it can be seen that, for example, the s-glass fiber, with an elongation to break of

5.3%, will require a resin with an elongation to break of at least this value to achieve

maximum tensile properties.

Figure 10: Selection criteria for the ideal resin system for a fiber

3.4.2 Adhesive properties of the resin system

High adhesion between resin and reinforcement fibers is necessary for any resin

system. This will ensure that the loads are transferred efficiently and will prevent

cracking or fiber / resin debonding when stressed.

3.4.3 Toughness properties of the resin system

Toughness is a measure of a materials resistance to crack propagation, but in a

composite this can be hard to measure accurately. However, the stress /strain curve of the

resin system on its own provides some indication of the materials toughness. Genera lly

the more deformation the resin will accept before failure the tougher and more crack-

resistant the material will be. Conversely, a resin system with a low strain to failure will


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tend to create a brittle composite, which cracks easily. it is important to match this

property to the elongation of the fiber reinforcement.

3.4.4 Environmental properties of the resin system

Good resistance to the environment, water and other aggressive substances,

together with an ability to withstand constant stress cycling, are properties essential to any

resin system. These properties are particularly important for use in a marine environment.

3.5 Resin types

The resins that are used in the fiber-reinforced composites can also be referred to

as polymers. All polymers exhibit an important common property in that they are

composed of long chain like molecules consisting of many simple repeating units .man

made polymers are generally called synthetic resins or simply resins. Polymers can be

classified under two types thermoplastic and thermosetting according to the effect of heat

on their properties.

Thermoplastics, like metals, soften with heating and eventually melt, hardening

again with cooling. This process of crossing the softening or melting point on the

temperature scale can be repeated as often as desired without any appreciable effect on

the material properties in either state. Typical thermoplastics include nylon,

polypropylene and abs, and these can be reinforced, although usually only with short,

chopped fibers such as glass.

Thermosettingmaterials, or, thermo sets, are formed from a chemical reaction in

situ, where the resin and hardener or resin and catalyst are mixed and then under go a

non-reversible chemical reaction to form a hard, infusible product. In some thermo sets,

such as phenolic resins, volatile substances are produced as by-products. Other

thermosetting resins such as polyester and epoxy, by mechanisms that do not produce any

volatile by products and thus are much easier to process. Once cured, thermo sets will not


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become liquid again if heated, although above a certain temperature their mechanical

properties will change significantly. This temperature is known as the glass transition

temperature (Tg), and varies widely according to the particular resin system used, its

degree of cure and whether it was mixed correctly. Above the Tg, the molecular structure

of the thermo set changes from that of a rigid crystalline polymer to a more flexible,

amorphous polymer. This change is reversible on cooling back below the Tg. Above the

Tg properties such as resin modulus drop sharply, and as a result the compressive and

shear strength of the composite does too. Other properties such as water resistance and

color stability also reduce markedly above the resins Tg.

Although there are many different types of resin in use in the composite industry,

the majority of structural parts are made with three main types, namely polyester, vinyl

ester and epoxy.

3.5.1 Polyester resins

Polyester resins are the most widely used resin systems, particularly in the marine

industry. By far the majority of dinghies, yachts and workboats built in composites make

use of this resin system. Polyester resin is the preferred material in marine industries

marine due to its superior. Polyester resin is the preferred material in marine industries

marine due to its superior water resistance.

Polyester resins are of the unsaturated type. Unsaturated polyester resin is a

thermo set, capable of being cured from a liquid or solid state when subject to the right

conditions. It is usual to refer to unsaturated polyester resins as polyester resins, or

simply as polyesters. There is a whole range of polyesters made from different acids,

glycols and monomers, all having varying properties. For use in molding polyester resin

requires the addition of several ancillary products. These products are generally a catalyst,

an accelerator and additives such as pigments and fillers.


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3.5.2 Epoxy resins

The large family of epoxy resins represents some of the highest performance

resins of those available at this time. Epoxies generally out-perform most other resin

types in terms of mechanical properties and resistance to environmental degradation,

which leads to their almost exclusive use in aircraft components. As a laminating resins

their increased adhesive properties and resistance to water degradation make these resins

ideal for use in applications such as boat building. Here epoxies are widely used as a

primary construction material for high-performance boats or as a secondary application to

sheath a hull or replace water-degraded polyester resins and gel coats.

The term epoxy refers to a chemical group consisting of an oxygen atom bon ded

to two carbon atoms that are already bonded in some way. the simplest epoxy is a three-

member ring structure known by the term alpha-epoxy or 1,2-epoxy. The idealized

chemical structure is shown in the figure below and is the most easily identified

characteristic of any more complex epoxy molecule.

Figure 11: Idealized chemical structure of a simple epoxy (ethylene oxide)

Usually identifiable by their characteristic amber or brown coloring, epoxy resins

have a number of useful properties. Both the liquid resin and the curing agents form low

viscosity easily processed systems. Epoxy resins are easily and quickly cured at any

temperature from 5c to 150c, depending on the choice of curing agent. One of the most

advantageous properties of epoxies is their low shrinkage during cure, which minimizes

fabric print-through, and internal stresses. High adhesive strength and high mechanical

properties are also enhanced by high electrical insulation and good chemical rsistance.

Epoxies find uses as adhesives, caulking compounds, casting compounds, sealants,

varnishes and paints, as well as laminating resins for a variety of industrial applications.


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Epoxy resins are formed from a long chain molecular structure similar to vinyl

ester with reactive sites at either end. In the epoxy resin, however, epoxy groups instead

of ester groups form these reactive sites. The absence of ester groups means that the

epoxy resin has particularly good water resistance. The epoxy molecule also contains two

ring groups at its center which are able to absorb both mechanical and thermal stresses

better than linear groups and therefore give the epoxy resin very good stiffness, toughness

and heat resistant properties.

3.6 Typical structural matrix resins

Table 3: Typical structural matrix resins

ResinTensile

strength

(Mpa)

Tensilemodulus

(Mpa)

Tg(k)

Thermo sets

Epoxy 103.4 4.1 463

Bismaleimide 82.7 4.1 547

Polyamide 137.9 4.8 630

Thermoplastic

Polynylene 65.5 4.3 366

Polyetheretherketon 70.3 1.1 400


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CHAPTER-4

EXPERIMENTAL INVESTIGATIONS

4.1 Fabrication techniques of composite materials

Various processes are available for making composite materials. The different

processes available for the fabrication of fiber-reinforced composites are

1) Hand lay-up

2) Vacuum bag moulding

3) Pressure bag moulding

4) Autoclave moulding:

4.1.1 Hand lay-up

Hand lay-up is the simplest process for making the composites laminates. The

selected fibers are wetted with resin and placed in the mould and entrapped air is removed

with rollers. Layers of glass and resin are added to build up to desired thickness and it is

normally allowed to cure at room temperature.


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Figure 12: Hand lay-up process

4.1.2 Vacuum bag moulding

In this method vacuum is used to eliminate voids and force out entrapped air and

excess resin. The component is first lay up in the mould with the resin, over the layers. Aseries of bleeders is placed, to provide a permeable space between lay-up and bag for

escape of evacuated air. A suitable sealing material such as cellophane of nylon is placed

over the lay-up and sealed at the edges. Vacuum is draw-in on the bag formed by the film,

and a laminate is formed. In this technique pressure less than atmosphere is possible.

4.1.3 Pressure bag moulding

In pressure bag moulding, usually a rubber bag is placed over the lay-up and

then at the pressure is applied to eliminate voids; force out entrapped air and squeezes

the excess resin. In pressure bag moulding higher pressure of the order of 100-mpa are

possible. Laminate with better mechanical properties are obtained.


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4.1.4 Autoclave moulding

Autoclave moulding is similar to vacuum bag moulding and it is a modification

of pressure bag moulding. Autoclave moulding refers to the process of lying of

reinforcing materials and resin matrix in required shape and quantity in suitable open

moulds and effecting the polymerization of the product with simultaneous application

of pressure, heat and vacuum. The entire operation is carried out in special equipment

called autoclave, which is essentially a pressure vessel with heating and evacuating

equipment.

The autoclave moulding can be employed where,

Large contoured, odd shaped parts are moulded.

Preparation of moulds or dies are difficult to make or expensive in construction.

4.2 Method adopted for fabrication

Usually the laminates can be prepared by lay-up techniques. But, the laminates

produced will have voids, cracks and may delaminate easily, applying pressure or

applying vacuum can overcome this. This can be achieved through by bagging the

laminates. This process is called vacuum bagging. A vacuum bag provides both pressure

up to 14.7psi, depending on your altitude and vacuum.

4.3 Accessories

4.3.1 Peel ply

One the laminate is in place; its time to apply the bag the first item to go down is a

peel ply. Peel plies are a tightly woven fabric, often nylon, and impregnated with some

type of release agent. The peel ply will stick to the laminate, but it will pull away without

to much difficulty.


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Peel ply is optional. Most often it is used to give the laminate a rough, rather than

smooth, finish. Many engineers consider this a bondable finish, and it usually passes a

wet out test.

If peel ply is used, it will absorb a small amount of resin, and this must be

accounted for. A net resin prepared may end up too dry. Peel ply specs should say how

much resin would be absorbed, in ounces per squire foot, or grams per squire meter.


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Figure 13: Modeling methods and tooling


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4.3.2 Release film

After the peel ply comes a layer of release film. This is a thin plastic, which has

been treated so it wont bond to the laminate. It is highly stretchable so it can conform to

complex geometries.

Peel ply can be either a solid sheet, or it can have perforations (in the latter case, it

is often called peel ply). The perforations might be like pin pricks, or they might be small

holes, which are punched out. The spacing can also vary from 2 inches to 8 inches.

Choose spacing based on the amount of resin that needs to be bled out: wet lay-ups can

use close spacing; prepared manufactures can recommend spacing for their particular

products; and net resin systems of course use imperforated release films.

Not all release films are compatible with every resin system. a few years ago, they

were preparing some cyan ate-ester test coupons, and the release film we normally used

for epoxies bonded to the coupons. You can also get release film treated so it will bond to

the laminate (bondable one side, bos, or bondable both sides, bbs). Bos can be used to

create a permanent release layer on composites tools, or as a moisture barrier on

laminates.

4.3.3 Bleeder and Breather

At least one layer of bleeder cloth goes above the release film. Bleeder is a thick,

felt like cloth. It purposes is to absorb excess resin. The bleeder also acts as a breather,

providing a continuous air path for pulling the vacuum. If the bag wrinkles agent against

the hard lament, it will trap air. The breather prevents this from happening.

The breather must be thick enough so that it does not become fully saturated with

resin. a thick breather is also desirable to keep resin from coming in contact with the bag.

It does not hurt anything if that happens, but preventing it makes the bag easier to

remove.


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4.3.4 Bag

The bag is the last item to be placed. Its a relatively thick plastic layer, available

in different amount of conformability. The bag is usually applied along one edge at a

time. Start at one corner and press the bag in to the other corner, removing the release

paper from the tape. As you move along the edge.

Be careful not to get any wrinkles in the bag or it will leak. Plates will be required

for anything but flat or simply curved structures. Make sure you remember to attach the

vacuum port (not shown in the figure) before closing the bag. The base of the port goes

inside the bag; cut a small cross in the bag for the attachment flange to fit through. If the

tool has an area for the port, make sure there is a breather path from the port to the part. If

the port goes on the part itself, put several layers of breather under the port to prevent

print through.


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CHAPTER-5

EXPERIMENTAL RESULTS

5.1 Introduction to testing

Depending up on the method of load application as a function of time,

mechanical testing can be divided into static, dynamic and fatigue testing. Static and

dynamic are primarily to the study of the extended effects of forces on rigid bodies, i.e.

the bodies for which the change in shape can be neglected.

In static tests, the load on the test specimen is either increased slowly and

progressively or maintained constant for a long time, with the result that the rate of test

piece strain is very low

In dynamics tests, the test piece is subjected to loading at considerable speeds,

so that the rate of strain is high. In case of fatigue tests, the piece is subjected to repeat

loading, which may vary in magnitude only or in magnitude and directions. Mechanical

tests differ also in the methods of load application. Tests in tension, compression,

bending, and torsion etc. are carried out to estimate the mechanical strength or at high or

low temperature, depending on the service conditions of the metals tested.

5.2 Purpose of testing

1) To access the quality of the material in order to prove a competitive marketing for

consumer goods.

2) Evaluate and optimize materials.

3) Evaluate and optimize marketing process variables.

4) To establish engineering design information.


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Figure 14: Stress- strain diagram

5.3 Test procedure

1. The parameters specified for the compression, tensile inter laminar and flexural

specimens are prepared according to the geometry.

2. Store the specimen in the conditioned environment until test time, if the testing

area environment is different than the conditioning environment.

3. Apply the load to the specimen at the specified rate until failure, while recording

data.

4. Record load verses strain continuously, or at frequent regular intervals.

5. Record the mode and the location of failure of the specimen.

6. Re-examine the means of load introduction in to the material if a significant

fraction of failures in a sample population occur with in one specimen width of the

tab or grip.

5.3.1 Sampling

Test at least 5 specimens per test conditions unless valid results can be gained

through the use of fewer specimens, such as in the case of a design experiment.


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5.3.2 Labeling

Label the coupons so that they will be distinct from each other and traceable

back to the raw material and in a manner that will both be unaffected by the test and not

influence the test.

5.4 Apparatus

5.4.1 Micrometers

A micrometer with a 4to5mm nominal diameter double-ball interface shall be

used to measure the thickness of the specimen. A micrometer with a flat anvil interface

shall be used to measure the width of the specimen. The accuracy of the instruments shall

be suitable for reading to within 1% of the sample width and thickness.

5.4.2 Testing machine

The testing machine shall be in conformance with practices e4, and shall satisfy

the following.

5.4.2.1 Testing machine heads

The testing machine shall have both an essentially stationary head and a movable

head.

5.4.2.2 Drive mechanism

The testing machine drive mechanism shall be capable of imparting to the

movable head shall be capable of being regulated.

5.4.2.3 Load indicator

The testing machine load-sensing device shall be capable of indicating the total

load being carried by the specimen. This device shall be essentially free from inertia-lag

at the specified rate of testing and shall indicate the load with accuracy over the load

range(s) of interest of within 1% of the indicated value. The load range (s) of interest

may be fairly low for modulus evaluation, much higher for strength evaluation, or both.


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5.5 Standard test methods for tensile properties of polymer matrix

composite material

ASTM D 3039/D 3039-00

5.5.1 Scope

This test method determines the in-plane tensile properties of polymer matrix

composite materials reinforced by high modulus fibers. The composite material forms

are limited to continuousfiber or discontinuous-fiber reinforced composites in which the

laminate is balanced and symmetric in respect to the test direction.

Figure 15: Standard test specimen details for tensile test

5.5.2 Summary of test method

A thin flat strip of material having a constant rectangular cross-section is mounted

in the grips of a mechanical testing machine and monotonically loaded in tension while

recording load. The ultimate strength of the material can be determined from the

maximum load carried prior to failure. If the coupon strain is monitored with strain or

displacement transducers then the stress-strain response of the material can be

determined, from which the ultimate tensile strain, tensile modulus of elasticity, Poissons

ratio, and transition strain can be derived.


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5.5.3 Significance and use

This test method is designed to produce tensile property data for material

specifications, research and development, quality assurance, and structural design and

analysis. Factors that influence the tensile response and should therefore be reported

include the following:

Material, methods of material preparation and lay-up, specimen stacking

sequence, specimen preparation, specimen conditioning, environment of testing, time at

temperature. Void content, and volume percent reinforcement properties, in the test

direction, which may be obtained from this test method include the following:

Ultimate tensile strength,

Ultimate tensile strain,

Tensile chord modulus of elasticity,

Poissons ratio, and

Transition strain.

5.5.4 Calculations

The tensile strength of the laminate can be calculated by using the relation,

f=p/bd

Where

f=Tensile strength in N/mm2

p= Max. load in N

b=Breadth of the tensile specimen in mmd=Thickness of the tensile specimen in mm


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Table 4: Tensile specimen geometry recommendations

Table 5: ASTM standards used for testing the laminates

Fiber

OrientationWidth

mm

Overall

Length

mm

Thickness

mm

Tab

Length

mm

Tab

Thickness

mm

Tab

Bevel

Angle

0

Unidirectional

15 250 1.0 56 1.5 7 or 90

90

Unidirectional

25 175 2.0 25 1.5 90

Balanced and

Symmetric

25 250 2.5 emery

cloth

----- -----

Random

Discontinuous

25 250 2.5 emery

cloth

----- -----

Type of test ASTM designation Length * width Thickness

Range

Tensile

Compressive

Flexural

In-plane shear

Interlaminar shear

d 3039/d 3039-00

d 3410-75

d 790-98

d 4255/d 4255m-83

d 2344-84

250 * 25.0 mm

120 * 12.5 mm

127 *1 2.7 mm

130 * 25.0 mm

020 * 10.0 mm

2-3 mm

2-3 mm

2-3 mm

2-3 mm

2-3 mm


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5.6 Standard test method for compressive properties of polymer matrix

composite material

ASTM D 3410/D 3410M

5.6.1 Scope

This test method determines the in-plane compressive properties of polymer

matrix composite materials reinforced by high modulus fibers. The composite materials

are limited to continuous fiber or discontinuous fiber re enforced composites in which the

laminate is balanced.

Figure 16: Standard test specimen details for compression test

5.6.2 Summery of test method

A flat strip of material having rectangular cross section is mounted in the grip of

the mechanical testing mission and monotonically loaded in compression while recording

load. The ultimate compressive strength of the material can be determined from the

maximum load carried to failure. If the coupon strain is monitored with strain or

displacement transducers than the stress stain of the response of the material can be

determined, from which the ultimate compressive strain, compressive modulus of

elasticity, Poissons ratio and transition strain can be determined.


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5.6.3 Significance and use

This test method is designed to produce the compressive property data for material

specification, research and development and quality assurance, and structural design and

analysis. Properties in the test direction, which may be obtained from this test method,

include the following

Ultimate compressive strength

Ultimate compressive strain

Modulus elasticity

Poissons ratio

Transition strain

5.6.4 Geometry

Table 6: Compression specimen geometry recommendations

Design of mechanical test coupons, especially those using end tabs remains to a

large extent. Each major composite testing laboratory has developed gripping methods for

the specific material systems and environments commonly encountered with in that

Fiber

Orientation

Width

mm

Gauge

Length

mm

Tab Length

mm

Overall

Length

mm

Tab

Thickness

mm0

Unidirectional 10 10-25 65 140-155 1.5

90

Unidirectional 25 10-25 65 140-155 1.5

Specially

Orthotropic 25 10-25 65 140-155 1.5


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Page No 42

laboratory. The compression tensile specimen geometry recommendations are shown in

the following table.

5.6.5 Calculations

The compressive strength of the laminate can be calculated by using the relation

f=p/bd

Where

f=Compressive strength in N/mm2

p= Max. load in N

b=Breadth of the tensile specimen in mm

d=Thickness of the tensile specimen in mm


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Figure 17: Standard test specimen details for flexural test

5.7.3 Calculations

The flexural strength S of the specimen is given by the formula

S=3pl/2bd2

Where

S=Stress in the outer fires at midspan in N/mm2

p=Load at a given point on the load-displacement curve in N

l=Support span in mm

b=Width of the beam tested in mm.

d=Depth of the specimen in mm.


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5.8 Standard test method for inter laminar shear properties of polymer

matrix composite material

ASTM D 2344

5.8.1 Scope

This test has been used for determining interlaminar shear strength of bi-

directional laminate specimens. It is believed applicable for any constant temperature at

which the constituent materials are structurally stable. Creep effects are neglected.

Polymeric composites with a laminated and fibrous structure have typical shortcoming in

their low shear resistance, especially in the planes where the properties of the materials

are determined by the matrix (resin). Hence shear strength gives the properties of resin

used.

The ILSS is used to determine the adhesive force at the matrix reinforcement

interface and tangential stresses acting at that interface therefore in the experimental

determination ofILSS, it is important to know the actual magnitude of tangential stresses

which can lead to the failure of the specimen. Because of its simplicity, it is used as a

quality control tool. It involves a three-point flexure specimen with the span to depth ratio

l/h, chosen to produce interlaminar shear failure. A complexity is presented by the short

beam shear method when used for laminated materials.

In particular, the ILSS will be parabolic within each layer, but a discontinuity in

slope will occur at the ply interfaces, as a result the maximum shear stresses will not

necessarily occur at the center. Laminated beam theory is hence required to calculate the

stresses. Thus, the short beam method is applicable only to polymeric and composite

materials, which can be treated as homogenous.

Practical experience showed that interlaminar shear failures are difficult to attain

at higher span to depth ratios. A specimen width maximum thickness of 6.4 mm is

required by ASTM standards. There is no such minimum thickness specified, hence

specimens as thin as 2.9 mm have been used.


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Figure 18: Standard test specimen details for flexural test

5.8.2 Interlaminar shear strength (ILSS)

The inter facial adhesion between the fiber and matrix resin was measured by

shunt beam there product binding test (ASTM D2344). The width of the specimen was 10

mm and the length was 20-mm. the crosshead speed for the test was 2 mm/min

5.8.3 Procedure

According to ASTM standards D-2344-76 the thickness and width of the

specimen is measured (to nearest 0.025) at the midpoint and the overall length of the

specimen is 20mm and width is 10mm.

The test specimen is placed in the test fixture and aligned so that its midpoint is

centered and long axis is perpendicular to the cylindrical axis or under the loading nose

push the side support into the span previously determined. (10mm). Apply the load to the

specimen at a crosshead rate of 2mm/min.the load to fracture the specimen (maximum

load, displacement on the indicating mechanism) is recoded.

5.8.4 Calculations

The inter laminar shear strength S is calculated by using the formula,

S= (3/4) (w/ab)

S=Inter laminar shear strength in kg/mm2

w=Breaking load in kg

a=Width of the specimen in mm

b= Thickness of specimen in mm


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BLISS UNIVERSAL TESTING MACHINE

Capacity: 1-50 KN

Figure 19: universal testing machine

FLEXURAL TEST TENSILE TEST COMPRESSION TEST
http://www.instron.in/wa/solutions/solutions_combos.aspx?ParentID=5&ChildID=97http://www.instron.in/wa/solutions/tension_testing_solutions_metals.aspxhttp://www.instron.in/wa/solutions/flexure_testing_solutions_metals.aspxhttp://www.instron.in/wa/solutions/solutions_combos.aspx?ParentID=5&ChildID=97http://www.instron.in/wa/solutions/tension_testing_solutions_metals.aspxhttp://www.instron.in/wa/solutions/flexure_testing_solutions_metals.aspxhttp://www.instron.in/wa/solutions/solutions_combos.aspx?ParentID=5&ChildID=97http://www.instron.in/wa/solutions/tension_testing_solutions_metals.aspxhttp://www.instron.in/wa/solutions/flexure_testing_solutions_metals.aspxhttp://www.instron.in/wa/solutions/solutions_combos.aspx?ParentID=5&ChildID=97http://www.instron.in/wa/solutions/tension_testing_solutions_metals.aspxhttp://www.instron.in/wa/solutions/flexure_testing_solutions_metals.aspx


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CHAPTER-6

RESULTS AND DISCUSSION

6.1 Laminating procedure

1. First the slab was cleaned thoroughly with acetone.

2. Then sealant was put around the required area to be kept under vacuum.

3. Wax was applied within the area enclosed with sealant.

4. The fabric was cut considering the required size and number of layers.

5. The weight of fabric was weighted and noted (wf).

6. The weight of matrix required (wm) was calculated based on the weight of fabric andthe fibre weight fraction.

7. The resin and hardener were mixed appropriately and the time was noted.

8. Teflon mat slightly bigger than the laminate being prepared was put in the area

enclosed with sealant and it was wet a little resin.

9. A single layer of the cut fabric was put on the Teflon mat and wet thoroughly.

10. This process was repeated until the required number of layers was wet (within the geltime of matrix). A Teflon mat was put over the wet layers.

11. Some waste fabric was put on it to absorb the excess resin.

12. This arrangement was covered with a polythene sheet.

13. A breather was put over the polythene sheet and covered with the vacuum bag.

14. Then vacuum was applied just before gelling for two hour.

15. Curing: the laminate was left overnight after removing the vacuum to cure at room

temperature.

16. Post curing: this was done by putting it in an oven at 85oc for two hours.

17. The specimens were cut according to the required size using band saw. Then they

Were ground and polished to the required dimensions. They were stored in airtight

Polythene bags and sent for testing.


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6.2 Fabrication details of JRP

6.2.1 Specifications of jute reinforced plastics

Materials

Reinforcement fibers: Jute fibers of 1 feet * l feet

Matrix: Resin LY 556 and HardenerHY 951

Process: Hand lay-up and Vacuum bagging at room temperature.

Number of layers: 6 layers of jute fibers.

6.2.2 Reinforcement details of jute reinforced plastics

Thickness of the jute fiber ply = 0.4 mm

No. of jute fibers = 6

Total thickness of the jute fiber ply = 6*0.4 mm

=2.4 mm

Weight of the jute fiber ply = 44 gms

No. of jute fibers = 6

Total weight of the jute fiber ply = 6*44 gms

= 264 gms

For 0.55 weight fraction of jute

The weight of the laminate = 264 gms


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6.2.3 Stacking sequence of jute reinforced laminate

Figure 20: Stacking sequence of jute reinforced laminate


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6.2.4 Matrix system details of jute reinforced plastics

For 0.45 weight fraction of matrix system

The weight of the matrix system =0.45*264/0.55

= 216 gms

Weight ratio of resin to hardener =100:12

Weight of the resin only =100*216/112

=193 gms

Weight of the hardener only =12*216/112

=23 gms

6.2.5 Time schedule for jute reinforced plastics

Resin mixed at =10.02 AM

Lay-up started at =10.08 AM

Lay-up completed at =10.40 AM

Vacuum applied (on) at =10.45 AM

Vacuum release (off) at =12.50 AM


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6.3 Fabrication details of GJRP

6.3.1 Specifications of glass jute reinforced plastics

Material

Reinforcement: Glass cloth E-grade (uni-directional),

Jute fiber of 1 feet* 1 feet

Matrix: Resin LY 556 and HardenerHY 951

Process: Hand lay-up and Vacuum bagging at room temperature.

Number of layers: 5 layers of Glass cloth and 4 layers of Jute cloth.

Mill used: 8 mill

6.3.2 Reinforcement details of hybrid

Thickness of the jute fiber ply = 0.4 mm

No. Of jute fibers = 4


=1.6 mm

Thickness of the glass fiber ply = 0.17 mm

No. Of glass fibers = 5


=0.85 mm


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6.3.4 Weight details of Hybrid

Weight of the jute fiber ply = 44 gms

No. Of jute fibers = 4

Total weight of the jute fiber ply = 4*44 gms

= 176 gms _________ R1

Weight of the glass fiber ply = 13.1 gms

No. Of glass fibers = 5

Total weight of the jute fiber ply = 5*13.1 gms

= 65.5 gms __________R2

Total weight of the reinforcement =R1+R2

=176+65.5

=241.5 gms

For 0.55 weight fraction of (jute+glass)

The weight of the laminate = 241.5 gms

5.3.5 Matrix system details of hybrid

For 0.45 weight fraction of matrix system

The weight of the matrix system =0.45*241.5/0.55

= 197.5 gms

Weight ratio of resin to hardener =100:12

Weight of the resin only =100*197.5/112

=176.5 gms

Weight of the hardener only =12*197.5/112

=21 gms


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