hybrid composite

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ABSTRACT

The Role of Materials in the Development of the modern industry is getting

overwhelming importance .This is because 40% of the total cost of product is used for

material. As technology becomes more and more sophisticated, the material used

should also be more efficient and is expected to have more performance efficiency and

reliability. Composite materials, plastics and ceramics have been dominant emerging

materials. The demand for new material for special engineering application is

increasing due to recent advances in space crafts, structural, automobile, IT and a host

of other industries.

The Modern need focuses on cheaper and flexible materials which perform in

stringent conditions of high temperature and pressure, in highly corrosive environment,

with higher strength but low weight, with wear resistance and longer durability. This

gives ample scope for fabrication of newer composites.

The present study is focused on fabrication of polymer composites as Epoxy

Resin blended with Glass and PET Woven fabric .In this project an attempt has been

made to fabricate the composite laminates by Vacuum Bag Moulding technique ,

because it one of the most versatile method of preparation of laminates, almost all the

laminates can be prepared by this method and it is also the most economical method of

preparation of laminates, but it involves a lot of labour work.

The laminates prepared by varying the weights of woven fabrics and Epoxy;

resin content has varied from 35% to 50% and were subjected to experiments to

determine mechanical properties and Non Destructive Evaluation. Data has been

tabulated and analyzed.

The properties evaluated from these tests have been systematically analyzed to

study the behavior and variation of properties with respect to its composition. This has

enabled us to derive to certain conclusions. With this study, we can conclude that

composites can successfully replace certain conventional metals in some structural and

aerospace applications.

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CHAPTER 1

INTRODUCTION

CHAPTER 1

INTRODUCTION

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1.1 COMPOSITE MATERIAL

Composite materials are materials made from two or more constituent materials with

significantly different physical or chemical properties which remain separate and

distinct on a macroscopic level within the finished structure.

There are two categories of constituent’s materials: matrix and reinforcement.

At least one portion (fraction) of each type is required. The matrix materials surround

and support the reinforcement materials by maintaining their relative position. The

reinforcement imparts special physical (mechanical and electrical) properties to

enhance the matrix properties. A synergism produces material properties unavailable

from naturally occurring materials.

The advantages of composites are that they usually the best quality of their

constituents and often some qualities that neither constituents possesses. The properties

that can be improved by forming a composite material include:

1. Specific properties –high strength, and strength to density ratio ,high

strength at high temperature.

2. High stiffness to density ratio ,toughness (impact and thermal shock)

3. Improved fatigue strength, , improved strength –rupture life.

4. Surface finish

5. Improved hardness with corrosion resistance and erosion resistance.

6. Improved Creep Strength.

7. Ability to tailor made specific properties.

8. Ability to use low cost tooling materials .

9. Composite can provide a specific tensile strength that is approximately 4 to

6 times greater than steel or aluminum.

10. Composites can provide a specific modulus i.e. 3.5 to 5 times greater than

steel or aluminum.

11. Tougher composites can have impact energies significantly higher than

metal alloys.

12. Design flexibility is greater and can allow for physical property and

dimensionally in part where desired .

13. Composite material has good sound dampening nature.

14. The need for machinery is eliminated or significantly reduced.

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The production of composite material is booming all over the world, i.e. the output

is increasing at a high rate every year. Although the cost of composite materials is

higher than standard materials, this is offset by the substantial advantages their

properties afford users such as light weight and resistance.

These serviceable properties have allowed composite materials to break into

major markets in automotive construction, aeronautics, and the building trade.

The control of the product life cycle from design to recycling, and the improved

characterization of the products and their performance are the requisites for considering

the substantial development programs.

The most primitive composite materials comprised straw and mud in the form

of bricks for building construction. The most advanced examples perform routinely on

spacecraft in demanding environments. The most visible application paves our

roadways in the form of either steel and aggregate reinforced Portland cement or

asphalt concrete. Those composite closest to our personal hygiene form our shower

stalls and bath tubs made of fiberglass. Solid surface, imitation granite and cultured

marble sinks and countertops are widely used.

Designing materials for specific application is the underlying philosophy of

composite materials. That is, composite materials are tailored for specific technological

needs. Composite provide designer, fabricator, equipment manufacturer and consumer

with sufficient flexibility to meet the demands presented by different environments and

special requirements. Thus they often eliminate the crippling necessity face by the

designers of restriction the requirements of design to traditional experience.

The goal in creating the composite is to combine similar or dissimilar materials

in order to develop specific properties that are related to desired characteristics. Since

composite can be designed to provide and almost unlimited selection of characteristics,

they are employed practically in all industries.

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Fig 1.1 Stress strain curves for fiber matrix and composites

Figure shows schematic representation of brittle fibre,ductile matrix and

combined effect of composites to obtain the properties and advantages stated

above.

1.2 OBJECTIVE

The main objective of this Project Work undertaken is to manufacture a hybrid

composite of optimum fiber resin composition by weight with high performance PET –

GF as the reinforcement and Epoxy as the resin which is expected to give the

following properties in both Longitudinal and Transverse directions.

1) High Mechanical Properties.

2) Outstanding Thermal Properties.

1.3 HISTORY

Although composite materials had been known in various forms throughout the

history of mankind, the history of modern composites probably began in 1937 when

salesmen from the Owens Corning Fiberglass Company began to sell fiberglass to

interested parties around the United States. Fiberglass had been made, almost by

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accident in 1930, when an engineer became intrigued by a fiber that was formed during

the process of applying lettering to a glass milk bottle.

The Owens Corning Fiberglass Company was formed in 1935 by Owens-

Illinois and Corning Glass Works to capitalize on this new fibrous material. A Japanese

company (Nitto Boseki) had also made fiberglass and was attempting to market the

fibers in Japan and the United States. The initial products for this finely drawn molten

glass were used as insulation (glass wool) but structural products soon followed.

The fiberglass salesmen realized that the aircraft industry was, in particular, a

likely customer for this new type of material because the many small and vigorous

aircraft companies seemed to be creating new aircraft designs and innovative concepts

in manufacturing almost daily with many of these innovations requiring new materials.

One company, Douglas Aircraft, bought the first roll of fiberglass shipped to the

west coast because they believed that the fiberglass would help them solve a production

problem. They had a bottleneck in the making of metal molds for their sheet metal

forming process (called hydro press forming). Each changed aircraft design needed

new molds and metal molds were expensive and had long lead times. Douglas

engineers tried using cast plastic molds, but they could not withstand the forces of the

forging process. Maybe if the plastic molds were reinforced with fiberglass they would

be strong enough to allow at least a few parts to be made so that the new designs could

be quickly verified. If the parts proved to be acceptable, then metal dies could be made

for full production runs. In collaboration with Owens Corning Fiberglass, dies were

made using the new fiberglass material and phenolic resin (the only resin available at

the time).

What a success! Reinforced plastic dies for prototype parts became the standard. Other

applications in cooling for aircraft soon followed. Many of the tools (jigs and fixtures)

for forming and holding aircraft sections and assemblies needed to be strong, thin and

highly shaped, often with compound curves. Metals did not easily meet all of these

criteria and so fiberglass reinforced phenolic tooling became the preferred material for

many of these aircraft manufacturing applications.

Not long afterward, unsaturated polyester resins became available (patented in

1936) and they eventually (although not immediately) became the preferred resin

because of the relative ease in curing these resins compared to phenolics. Peroxide

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curing systems were already available with benzoyl peroxides being patented in 1927,

lauroyl peroxide in 1937, and many other peroxides following not too long afterward.

Higher performance resin systems also became available about this time with the

invention of epoxies in 1938. The materials and the applications seemed to be

converging at the same time.

1.3.1 Developments during World War II

The pace of composite development, already fast, was accelerated during World

War II. Not only were even more aircraft being developed and, therefore, composites

more widely used in tooling, but the use of composites for structural and semi-

structural parts was being explored and then adopted. For instance, in the frantic days

of the war, among the last parts on an aircraft to be designed were the ducts. Since all

the other systems were already fixed, the ducts were required to go around the other

systems, often resulting in ducts that were convoluted, twisting, turning, and placed in

the most difficult to access locations. Metal ducts just couldn’t easily be made in these

“horrible” shapes. Composites seemed to be the answer. The composites were hand

layup on plaster mandrels which were made in the required shape. Then, after the resin

had cured, the plaster mandrels were broken out of the composite parts. Literally

thousands of such ducts were made in numerous manufacturing plants clustered around

the aircraft manufacturing/assembly facilities.

Other early WWII applications included engine nacelles, which lightened the A-

20 airplane and radomes (domes to protect aircraft radar antennas) which gave both

structural strength and radar transparency. Phenolic-reinforced paper was used to make

a structural wing box beam for the PT-19 airplane at about this time. Plastic airplane

seats using combed and carded cotton fibers impregnated with urea and polyester were

also made on an Air Force contract during the early war years. Non-aircraft

applications included cotton-phenolic ship bearings, asbestos4 phenolic switchgears,

cotton/asbestos-phenolic brake linings, cotton-acetate bayonet scabbards, and

thousands of others.

The early war period also marked the first production of a fiberglass reinforced

boat molded by Basons Industries. However, when molding the boat, no mold release

or parting agent was used and the part could not be extracted from the mold. After all

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attempts to separate the part from the mold had failed, the entire assembly was rolled

into the Bronx River.

At about this time (1942), the government became concerned that supplies of

metals for aircraft may not be available and so they instructed the engineers at Wright

Patterson Air Force Base to survey all of the manufacturers of composite parts in the

United States and try to determine the current best practices in composite manufacture.

Wright Patterson personnel were also to remote the use of composites by developing

design rules, by encouraging the development of new composite materials and

applications, and by using their own expertise for the development of new and bold

composite applications. Perhaps the boldest applications of all were the development of

aircraft wings for the AT-6 and the BT-15, two training airplanes. A total of six wing

sets were made, installed on aircraft, and successfully flown. In spite of the success of

this project, aircraft structural parts were not made again for 50 years. Even more

amazing, after the 50 year hiatus, the method of making the parts was nearly identical

to the method employed at Wright Patterson Air Force Base in 1942.

Many other composite improvements were developed during WWII including

some Innovative manufacturing methods such as filament winding and spray-up.

Sandwich structures using a cellular core, fire resistant composites, and prepared

materials were also developed during this time of development opportunity.

1.3.2 Post World War II Developments

When the war effort came to a sudden halt, the many companies who had been

active in making war materials were faced with an acute problem. They needed to

quickly identify new markets and new products which utilized the expertise they had

developed. Companies like Goldsworthy Engineering were trying to make any

composite part they could think of and were receiving support from the companies who

manufactured fiberglass who would “sponsor” some of the projects. For instance, the

fiberglass manufacturers would pay for the tooling for a new application just to reduce

the development cost.

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Some of the war-oriented applications were converted directly to commercial

applications such as fiberglass reinforced polyester boats. By 1948 several thousand

commercial boats had been made.

Almost everyone agreed that the pent-up demand for automobiles was a logical

application for composites. By 1947 a fully composite body automobile had been made

and tested. This car was reasonably successful and led to the development of the

Corvette in 1953 which was made using fiberglass performs which were impregnated

with resin and molded in matched metal dies. Eventually the dominant molding method

for automobile parts was compression molding of sheet molding compound (SMC) or

bulk molding compound (BMC). Premix materials of these types were developed as

early as 1948 by the Galstic Corporation. One automotive innovation that deserves

special mention is the auto/plane development led by Convair Aircraft Company.

Convair reasoned that the many returning wartime pilots would like to continue with

their flying, but would also like to combine it with family vacations. Hence, Convair

made an automobile with an all-composite body (for weight savings) that would allow

a special wing assembly to be attached. The wings would be available for rent at

various airports, thus permitting the driver to rent a wing assembly at one airport, fly to

the vacation site, turn in the wing assembly, and drive away. Prototypes were made and

successfully demonstrated. What a boon they would be today in Los Angeles, although

the skies might be more hazardous than the roads!

Some of the products made during the post-war era have now emerged as major

markets for composite materials. These include tubs and shower assemblies, non-

corrosive pipes, appliance parts, trays, storage containers, and furniture. Other

composite products have also been successful, although not quite as well known or

spectacular. For instance, sets for entertainment groups and stage productions,

especially those that travelled like the Ice Follies, were made of composites. In the

movie “Captain from Castile” the armor and helmets of the Spanish soldiers were made

of composites and painted to resemble metal. The headdresses of the Aztecs were also

molded composites.

Several innovative manufacturing methods were also developed in the late

1940's and early 1950's including pultrusion (by Goldsworthy), vacuum bag molding,

and large-scale filament winding.

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1.3.4 AEROSPACE

The push for aerospace dominance that began in the 1950's and really picked up

speed in the 1960's was a new impetus for composite development. Richard Young of

the W. M. Kellogg Company began using filament winding for making small rocket

motors. This technology was purchased by Hercules and was the basis for the large-

scale rocket motor business which was at the heart of the space race. By 1962 the need

for highly accurate filament winding machines became apparent to Larry Ashton, an

engineer at Hercules, who founded Engineering Technology to produce these

machines. (Engineering Technology was started from an initial stake of money the

founders obtained from selling their blood to a blood bank. That’s giving it all for the

company!)

In 1961 a patent was issued to A. Shindo for experimentally producing the first

carbon (graphite) fiber but Courtalds Limited of the United Kingdom was the first to

produce commercially viable carbon fibers several years later. With these fibers, part

stiffness to weight was improved and even more applications in aerospace were

introduced. Perhaps the crowning jewel of this period (1978) was the development of

the first fully filament wound aircraft fuselage, the Beech Starship, by Ashton. The

plane was successfully flown, but was not commercialized using the filament wound

technology. Many people still believe that the filament winding technology is the best

method to produce small aircraft fuselages.

1.3.5 Leading Up To the Present

New fibers were also introduced with boron filaments becoming available in

1965 and aramid fibers (Kevlar®) offered commercially by DuPont in 1971. Fibers

made from ultra high molecular weight polyethylene were made in the early 1970's.

These advanced performances fibers, along with fiberglass and carbon fibers, have led

to tremendous developments in aerospace, armor (structural and personal), sports

equipment, medical devices, and many other high performance applications. The

development of new and improved resins has also contributed to the expansion of the

composites market, especially into higher temperature applications and applications

where high corrosion resistance is needed.

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Today, the composites marketplace is widespread. As reported recently by the

SPI Composites Institute, the largest market is still in transportation (31%), but

construction (19.7%), marine (12.4%), electrical/electronic equipment (9.9%),

consumer (5.8%), and appliance/business equipment are also large markets. The

aircraft/aerospace market represents only 0.8% which is uprising in light its importance

in the origins of composites. Of course, the aerospace products are fewer in number but

are much higher in value. Most of the markets continue to grow. Composites have

found their place in the world and seem to be gaining market share, especially in

products where performance is critical. Some of these products are very new, but isn’t

it interesting that construction is still a major market for composites, just as it was in

1500 B.C. when the Egyptians and Israelites were using straw to reinforce mud bricks.

1.4 Classification of composites

1.4.1 Based on Micro Structure

The microstructure of the composite provides a basis for classifying them for

purpose of study, processing and analysis. Two materials can be combined only by two

ways:

By inserting one material into other

1. By bonding them layer by layer

The former type of composition is called multiphase composition and other

type is multi-layered composition .The phase composition is generally at microscopic

level and the layered composition at macroscopic level.

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1.4.2 Based on methods of Manufacturing

Natural composite

These are composite materials, which exist in nature .wood, bone, muscle, skin,

shell powder of the beetle nut and coconut, wheat rice coconut, wheat rice coffee and

fibers of sisal, coir, jute, etc are the examples of natural composites. The nature fibers

such as sisal, jute, coir etc provide strength to the composite through high transfer

efficiency between the matrix and the fiber. These natural fibers generally used as

reinforcement and they improve the toughness and flexural strength of the composite

materials also they have a cellular structure and they can impart sound dampening

properties to the composite. Another advantage of reinforcing these lingo cellulose

materials in polymer matrix is that these composites have a wood like texture and can

be used as substitute for wood.

Man made composite

These composites are the new family of composites created by man. Man made

composite offer considerable freedom in the design and hence, they are of greater use.

More than 200 families of composites have been made by man for his use. Man made

composites can be further classified into two groups

1. Those in which the constituents are separately made and then combined

into composites.

2. Those in which the insert in the form of fiber are grown within the matrix.

The eutectic metallic composite and self-reinforced polymer is examples

of latter category of composites.

1.5 Importance of composite

Composites have several properties and characteristics feature that make them

stand above all other conventional material both in performance efficiency and in the

manufacturing adaptability. Some of the attributes are given below.

1. Composites are multi-functional materials. The fact that several

functional requirements can be obtained by one single material make

the designs easy and the product functionally efficient.

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2. Composite are generally energy efficient because of their lightness,

they require less energy for transportation, erection and operation.

3. Composite generally can be made corrosion and weather resistant. As

a result, they are durable and require less maintenance

4. Composites can be designed to give properties for specific design

conditions

5. By proper orientation of fibers, directional properties can be obtained.

Products of complex shapes can be molded without any material

wastage part consolidation and close tolerances can also be

maintained.

1.6 Fiber reinforced composite material

Major constituents in a fiber-reinforced composite material are the reinforcing

fibers and a matrix, which acts as a binder for the fibers. Other constituents that may

also be found are coupling agents, coatings and fillers. Coupling agents and coatings

are applied on the fibers to improve their wetting with the matrix as well as to promote

bonding across the fiber/matrix interface. Both in turn promote a better load transfer

between the fibers and reduce cost and improve their dimensional stability.

In general, fibers are the principal load-carrying members. While the

surrounding matrix keeps them in the desired in the desired location and orientation,

acts as a load transfer medium between them, and protects them from environmental

damages due to elevated temperatures and humidity for example.

1.6.1 Fibers

The fiber is an important constituent in composites. A great deal of research

and development has been done with the fibers on the fibers on the effects in the types,

volume fraction, architecture and orientation. The fiber generally occupies 30%-70% of

the matrix volume in the composites. The fibers can be chopped, woven, stitched

and/or braided. They are usually treated with sizing such as starch, gelatin, oil, or wax

to improve the bond as well as binders to improve the handling .The most common

types of fibers used in advanced composites for structural applications are the

fiberglass, aramid and carbon. The fiberglass is the least expensive and carbon being

the most expensive. The cost of aramid fibers is about the same as the lower grades of

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the carbon fiber. Other high strength, high modulus fibers such as boron are at present

time considered to be economically prohibitive.

1.6.2 Resins

The use of particular resin will determine the properties and range of conditions

over which the Fiber reinforced polymer materials can be used. Resins are

commercially available in a variety of forms, as powder, flakes, granules, water

emulsions and latexes, solutions in organic solvents and in liquid form covering a wide

range of viscosities.

Properties of resins vary greatly and determine the conditions under which

fabricating or molding a particular mixture can be done. For example, many resins

generate volatiles during curing. As such, high molding pressures are necessary to

prevent by-products from forming gas pockets in the product.Resins that can be used at

low pressures are most often preferred for FRP molding. Molding equipment at low

pressure is less costly and simpler in design.

CHAPTER 2

LITERATURE SURVEY

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CHAPTER 2

LITERATURE SURVEY

Johns Manville's Engineered Products Group in Denver has introduced

Comfil-G, a family of commingled yarns consisting of continuous glass and PET

filaments. Another Comfil-G product with glass and polypropylene filaments will be

introduced this year.

Johns Manville says the glass/PET product can be used to produce lightweight plastic

molds with improved tensile strength

It can also be used for pultrusion, hot-press forming, winding, and braiding.

Glass/PET yarn resists temperatures up to 120 C (248 F). It also reportedly provides

good paintability and adhesive bonding.

The Fracture Behavior of Glass Fiber/Recycled PET Composites.

W. J. Cantwell Department of Engineering, University of Liverpool, Liverpool L69

3BX, United Kingdom.

http://encyclopedia2.thefreedictionary.com/Adhesive+bonding

http://encyclopedia.thefreedictionary.com/Pultrusion

http://encyclopedia2.thefreedictionary.com/tensile+strength

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They Investigated potential offered by glass fiber reinforced composite

materials based on a recycled PET matrix has been investigated. Laminates containing

both woven glass fabrics and chopped strand mats have been manufactured and tested

under both quasi-static and impact conditions. Polished sections from a number of

laminates have highlighted the high degree of fiber wetting and the low level of voiding

in the laminates. Three point bend tests and Charpy impact tests on simple beam-like

samples have shown that recycled polymer composites offer a range of mechanical

properties similar to those associated with corresponding laminates based on virgin

polymer matrices. A series of interlaminar fracture tests on the woven fiber composites

have shown that the delamination resistance of these materials is comparable to that

exhibited by relatively tough systems such as carbon fiber reinforced PEEK.

Glass fibre recycled poly(ethylene terephthalate) composites: mechanical and thermal

properties by A.L.F. de M. Giraldi, Department of Polymer Technology, College of

Chemical Engineering, State University of Campinas, SP, Brazil.

Their Investigations of thermal and mechanical properties of recycled

poly(ethylene terephthalate) (PET) reinforced with glass fibre have been carried out,

focusing on the influence of two variables involved in the extrusion process: screw

speed and torque. A Factorial Experimental Design of the processing conditions during

extrusion (screw speed and torque) was done to get the best thermomechanical

properties versus processing conditions. Mechanical properties such as Young's

Modulus and Impact Resistance increased after the addition of glass fibre in recycled

PET matrix.

Interlaminar fracture of commingled-fabric-based GF/PET composites

L. Ye and K. Friedrich Department of Mechanical and Mechatronic Engineering at the

University of Sydney, NSW 2006, Australia,Institute for Composite Materials Ltd,

University of Kaiserslautern, Germany.

A 45:55 weight% mixture of commingled glass/polyethylene terephthalate

(PET) fabric was selected to study the relationships between material microstructure,

Mode I and Mode II interlaminar fracture toughnesses and failure mechanisms.

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Composite laminates subjected to different cooling histories were manufactured within

a steel mould using a laboratory heat press. Mode I and Mode II interlaminar fracture

tests were performed using double cantilever beam and end-notched flexure specimens.

PET matrix morphology appeared to be sensitive to the thermal histories, although this

occurred on a subspherulitic scale (in contrast to observations made with

polypropylene-based composites). The spherulitic textures were generally very fine and

no evidence of interspherulitic fracture paths could be identified. When the composites

were subjected to low cooling rates or an isothermal crystallization process, many small

matrix cracks developed between fibres within the reinforcing bundles. The lower the

cooling rate, the higher the density of matrix cracks per unit volume of material. The

interlaminar fracture toughness in the laminates with slow cooling rates was much

lower than in the case where a quasi-quenched condition was applied.

Characterization of thermoplastic poly(ethyleneterephthalate)-glass fibre composites,

crystallization study By Catherine Gauthier , Laboratoire d'Etudes des Matériaux

Plastiques et des Biomatériaux, Université Claude Bernard,France.

They investigated the influence of glass fibers on crystallization kinetics and on

matrix morphology for poly(ethylene terephthalate) (PET)/glass fibre composites. The

following parameters are also considered: fusion-crystallization conditions, thermal

stability and the addition of nucleating agents in the matrix (talc or sodium benzoate). It

clearly appears that the influence of those additives on the crystallization of PET is

predominant compared to the effect of stiffening fibres. Moreover, the application of

shear stresses at the PET/glass fiber interface promotes the growth of a different

crystalline superstructure.

2.1 Scope of Present Study

A probe by accident into the field of thermosetting polymers has brought

about a quantum growth in its basic as well as technological aspects .The synthetic

thermosetting polymers with the combinational properties of the existing conventional

high strength polymers and glass fibers with a variety of filler materials have altogher

offered a new field of research.

The review work presented here reveals that bulk of the effort has gone into

the understanding of the mechanical ,thermal and physical properties of

thermosets .A thorough literature search reveals that there are no systematic

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studies on mechanical properties of thermosetting composites .There is ample

scope for fabrication of newer composites with different weight fractions of

glass fiber and PET in polymers and there characterization for

physical ,mechanical and thermal properties .In this thesis ,a wealth of data on

properties of polymer glass PET composites has been generated .These data are

useful for material technologists and A probe by accident into the field of

thermosetting polymers has brought about a quantum growth in its basic as well as

technological aspects .The synthetic thermosetting polymers with the combinational

properties of the existing conventional high strength polymers and glass fibers with

a variety of filler materials have altogher offered a new field of research.

The review work presented here reveals that bulk of the effort has gone into

the understanding of the mechanical and thermal properties of thermosets .A

thorough literature search reveals that there are no systematic studies on

mechanical properties of thermosetting composites .There is ample scope for

fabrication of newer composites with different weight fractions of glass fiber

and fillers in polymers and there characterization for physical ,mechanical and

thermal properties .In this thesis ,a wealth of data on mechanical properties of

polymer glass filler composites has been generated .These data are useful for

material technologists ,mechanical engineers and defence engineering ,who can

make use of this database for the generation of new materials for specific

application. In that respect it has been used GF and virgin PET fibers in the form of

woven mat and epoxy as matrix .Laminates are obtained from vacuum bag moulding

technique . Tests carried out to evaluate Physico-Mechanical and thermal properties

according to ASTM standards.

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CHAPTER 3

MATERIALS USED

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CHAPTER 3

MATERIALS USED

3.1 Glass fiber

The most common and inexpensive fiber used is glass fiber, usually for the

reinforcement of polymer matrices. Typical composition of glass fibers is 50-60% SiO2,

and other oxides of Al, Ca, Mg, Na, etc.Glass fibers are produced by melting the raw

materials in a reservoir and feeding into a series of platinum bushings. Each of which

has several hundred holes in its base. The glass flows under gravity and line filaments

are drawn mechanically downwards as the glass extrudes from the holes. The fibers are

wound onto a drum at speeds of several thousand meters per minute. Control of the

fiber diameter is achieved by adjusting the head of the glass in the tank, the viscosity of

the glass (dependent on composition and temperature), the diameter of the holes and

the winding speed .

Properties Values

Specific gravity 2.54-2.56

Tensile strength 260-360 KN/m *10

Modulus of elasticity 7.0-7-3 KN/m *10

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Index of refraction 1.547

Softening point 1555F

Table 3.1 .Typical properties of E-glass fibre .

Typical compositions of three types of glass popular for composites are given.

The most commonly used E-glass (E for electrical), draws well and has good strength,

stiffness, electrical and weathering properties. In some cases, C-glass (C for corrosion)

is preferred, having better resistance to corrosion than E-glass, but lower strength.

Finally, S-glass (S for strength) is more expensive than E-glass, but has a higher

strength, Young’s modulus and temperature resistance. The strength and modulus are

determined primarily by the atomic structure. Silica-based glasses consist primarily of

covalently bonded tetrahedron, with silicon at the centre and oxygen at the corners.

Addition of alkali and alkaline earth metals such as K, Na and Ca tends to lower the

stiffness and strength, but improves the formability. The strength depends on

processing conditions and test environment. Freshly drawn E-glass fibers, provided

they are handled very carefully to avoid surface damage, have strength of 3.5 GPa and

the variation in strength is almost zero. The strength falls in humid air, owing to the

adsorption of water on the surface.

A major factor determining the strength is the damage which fibers sustain when they

rub against each other during processing operation. To minimize this damage, glass

fibers are usually treated with a size at an early stage in manufacture. This is a thin

coating applied to the fibers by spraying with water containing an emulsified polymer.

Glass fibers are available as

a) Chopped Strands

b) Continuous Yarn

c) Roving

d) Fabric Sheets

constituents E glass S glass C glass

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Sio2 54 64 65

Al2o3 15 25 4

Cao 17 <0.1 14

Mgo

B2o3

Others

4.5

8

1.5

10

-

0.8

3

5

8

Table 3.2 Chemical composition of types of glass in weight percentage

Figure : Glass Fiber

3.2 Polyethelene terepthalate (PET)

PET exists both as an amorphous (transparent) and as a semi-crystalline

(opaque and white) thermoplastic material. Generally, it has good resistance to mineral

oils, solvents and acids but not to bases. It has good barrier properties against oxygen

and carbon dioxide. Therefore, it is utilized in bottles for mineral water. Other

applications include food trays for oven use, roasting bags, audio/video tapes as well as

mechanical components. Repeating unit of PET is as the following:

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Glass transition temperature: 76oC.

Melting temperature: 250oC.

Amorphous density at 25oC: 1.33 g/cm3.

Crystalline density at 25oC: 1.50 g/cm3.

Molecular weight of repeat unit: 192.2 g/mo

Fig: PolyEthelene Teraphtelete

3.2.1General Polyester Fiber Characteristics:

Strong

Resistant to stretching and shrinking

Resistant to most chemicals

Quick drying

Crisp and resilient

Wrinkle resistant

Mildew resistant

Abrasion resistant

Retains heat-set pleats and crease

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Easily washed

3.2.2 Relationship between Structure, Properties And Processing

Parameters of PET Fibers.

Properties of polyester fibers are strongly affected by fiber structure. The fiber

structure, which has a strong influence on the applicability of the fiber, depends heavily

on the process parameters of fiber formation such as spinning speed (threadlike stress),

hot drawing (stretching), stress relaxation and heat setting (stabilization) speed.

As the stress in the spinning threadlike is increased by higher wind-up speed, the PET

molecules are extended, resulting in better as-spun uniformity, lower elongation and

higher strength, greater orientation and high crystallinity. Hot drawing accomplishes

the same effect and allows even higher degrees of orientation and crystallinity.

Relaxation is the releasing of strains and stresses of the extended molecules, which

results in reduced shrinkage in drawn fibers. Heat stabilization is the treatment to "set"

the molecular structure, enabling the fibers to resist further dimensional changes. Final

fiber structure depends considerably on the temperature, rate of stretching; draw ratio

(degree of stretch), relaxation ratio and heat setting condition. The crystalline and

noncrystalline orientation and the percentage of crystallinity can be adjusted

significantly in response to these process parameters.

3.2.3 Mechanical and Physical Properties

As the degree of fiber stretch is increased (yielding higher crystallinity and

molecular orientation), so are properties such as tensile strength and initial Young's

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modulus. At the same time, ultimate extensibility, i.e., elongation is usually reduced.

An increase of molecular weight further increases the tensile properties, modulus, and

elongation. Typical physical and mechanical properties of PET fibers are given in

Table 2. And stress-strain curves in Fig. 4. It can be seen that the filament represented

by curve C has a much higher initial modulus than the regular tenacity staple shown in

curve D. On the other hand, the latter exhibits a greater tenacity and elongation. High

tenacity filament and staple (curve A and B) have very high breaking strengths and

moduli, but relatively low elongations. Partially oriented yarn (POY) and spun filament

yarns, exhibit low strength but very high elongation (curve E). When exposing PET

fiber to repeated compression (for example, repeated bending), so-called kink bands

start to form, finally resulting in breakage of the kink band into a crack. It has been

shown in that the compressibility stability of PET is superior to that of nylons.

Filament yarn Staple and tow

Property Regular

tenacitya

High

tenacityb

Regular

tenacityc

High

tenacityd

breaking tenacity N/tex 0.35-0.5 0.62-0.85 0.35-0.47 0.48-0.61

breaking elongation 24-50 10-20 35-60 17-40

elastic recovery at 5% elongation, % 88-93 90 75-85 75-85

initial modulus, N/texf 6.6-8.8 10.2-10.6 2.2-3.5 4.0-4.9

specific gravity 1.38 1.39 1.38 1.38

Moisture regian, % 0.4 0.4 0.4 0.4

Melting temperature, oC 258-263 258-263 258-263 258-263

Table 3.3: Physical Properties of Polyester (PET) Fibers

3.3 EPOXY (LY556)

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 resin their increased adhesive properties and

resistance to water degradation make these resins ideal for use in applications such as

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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 bonded 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 idealised

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

characteristic of any more complex epoxy molecule.

Fig.3.1-Chemical Structure of simple Epoxy

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 5°C to 150°C,

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 resistance. Epoxies find uses

as adhesives, caulking compounds, casting compounds, sealants, varnishes and paints,

as well as laminating resins for a variety of industrial applications.

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

with reactive sites at either end. In the epoxy resin, however, these reactive sites are

formed by epoxy groups instead of ester groups. 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 centre which are able to absorb both mechanical and

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thermal stresses better than linear groups and therefore give the epoxy resin very good

stiffness, toughness and heat resistant properties.

The figure below shows the idealised chemical structure of a typical epoxy. Note the

absence of the ester groups within the molecular chain.

Fig.3.2-Molecular configuration Epoxy

Epoxies differ from polyester resins in that they are cured by a 'hardener' rather than a

catalyst. The hardener, often an amine, is used to cure the epoxy by an 'addition

reaction' where both materials take place in the chemical reaction.

The chemistry of this reaction means that there are usually two epoxy sites binding to

each amine site. This forms a complex three-dimensional molecular structure.

Since the amine molecules 'co-react' with the epoxy molecules in a fixed ratio, it is

essential that the correct mix ratio is obtained between resin and hardener to ensure that

a complete reaction takes place. If amine and epoxy are not mixed in the correct ratios,

unreacted resin or hardener will remain within the matrix which will affect the final

properties after cure. To assist with the accurate mixing of the resin and hardener,

manufacturers usually formulate the components to give a simple mix ratio which is

easily achieved by measuring out by weight or volume.

3.3.1 Properties of Epoxy Resin:

1. Tensile Strength (MPa) 69.5

2. Flexural Modulus (MPa) 12400

3. Tensile Elongation (%) 0.40 to 7.9

4. Modulus of Elasticity (MPa) 3416

5. Compressive Strength (MPa) 121

6. Flexural Strength (MPa) 79.5

3.4 Hardener(HY 951)

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Its trade name is Araltide Hardener HY951 belongs to polyamine family. It is intended

to use for epoxy curing agent.

Chemical (IUPAC) name : 1,2-Ethanediamine,N,N’-bis(2-aminoethyle)

Specific gravity:0.982g/mL at 25°C

Boiling temperature: Less than 200°C

Araldite LY 556 is an unfilled non modified epoxy resin of low viscosity

for the laying up of the laminates which may be converted to solid ,infusible state

with hardener HY951 ,HY 972 ,HY 974,and HZ 978.The choice of the hardener

depends on the pot life, curing temperature and heat resistance required .The

viscosity of the resin may be reduced considerably by addition of ARALDITE

DY 021.

Curing takes place either at room temperature or at an elevated

temperature ,depending on the hardener used .No volatile substance are split off

therefore little or no pressure is required for curing .

Due to the very low shrinkage .ARALDITE LY556 /glass fibro laminates

are dimensionally stable and practically free from internal stress

Cured glass laminates based on ARALDITE LY 556 posses good

mechanical and electrical properties .They are resistant to weathering ,Humidity

and many chemicals. They do not cause corrosion and have low thermal

conductivity and a low burning rate .Laminates may be colored with

ARALDITE coloring pastes and are easy to machine.

3.5 Woven Fabrics

3.5.1 Plain or taffeta: The wrap and fill yarns cross alternately .The weave

provides fabric stability and firmness with least yarn slippage .Strength is

provided equally in two directions (if yarn size and count are equal in both

directions) and resin penetration into the weave is adequate .

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3.5.2Basket:This is similar to plain weave expect that two or more wrap yarns

are woven as one over and under two or more fills yarns .This weave has

somewhat better and pliability than plain weaves

3.5.3 Twill: Figure shows a 3*1 twill ,but others such as 21, 282 etc .. are

possible .this has better drape than plain or basket weaves but is more difficult

to wet .

3.5.4 Leno:The wrap yarns are twisted

around each other ,locking the filler

yarns in the place.

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3.5.5 Long-shaft satin:This weave gives good drape and stretch in all

directions but is less open than other weaves .It is used for countoured surfaces

such as radar randomes.

Fig3.4: Leno weave Fig3.5:Long shaft satin weave

The fabric weaved was plain weave with glass fibre as warp

and PET as a weft .The proportion of glass and PET are in the ratio of 66:34 by weight

.The fabric has a mass per unit area of 260 gsm (grams per square meter) with the

overall fabric width of 1270 mm and length of 7 meters.the thickness of fabric is

0.40mm.The schematic photograph of woven fabric is shown in the figure .

Glass fiber

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CHAPTER 4

FABRICATION PROCESS

PET

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CHAPTER 4

FABRICATION PROCESS

In order to meet the market need, researchers and industries are developing a

great number of manufacturing techniques. The costs of production, as a considerable

part of total costs, usually determine which will be followed for a product. Different

processes usually take either low capital investment with high labor, or high capital

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investment with low labour.Each of the fabrication processes has charecterstics that

define the type of products be produced.

4.1 Some common fabrication techniques for composites are:

Hand lay-up on open mold

Hand layup assisted by vacuum bagging

Resin infusion

Spray-up

RTM and VARTM

Hot press molding

Cold/warm press molding

Filament-Winding

Pultrusion

Autoclave

Laminates are prepared by Hand layup assisted by vacuum bagging process

4.2 Vacuum bagging Moulding:

Vacuum bag molding, a refinement of hand lay-up, uses a vacuum to eliminate

entrapped air and excess resin. After the lay-up is fabricated on either a male or female

mold from precut plies of glass mat or fabric and resin, a nonadhering film of polyvinyl

alcohol or nylon is placed over the lay-up and sealed at the mold flange. A vacuum is

drawn on the bag formed by the film while the composite is cured at room or elevated

temperatures. Compared to hand lay-up, the vacuum method provides higher

reinforcement concentrations, better adhesion between layers, and more control over

resin/glass ratios. Advanced composite parts utilize this method with preimpregnated

fabrics rather than wet lay-up materials and require oven or autoclave cures. The

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improvement in strength/weight ratio is so great, that the product can be classified even

as “aerospace quality”. The process is particularly useful for small production runs and

prototyping.

4.3 Materials required

Glass+PET fiber woven mat cut to required size

Epoxy Resin(LY556)

Hardner(HY951)

Mould releasing agent

Sealant

4.4 Auxiliaries required:

Mixing bowl

Weighing machine

Stirrer

Brush

Hand gloves

Roller

Waste cotton

Plastic sheets

Vacuum pump

4.5 Procedure to prepare laminates:

Glass and PET is woven in the form of cloth is cut into laminates of size

315mm*315mm.

The surface is cleaned to make sure there is no oil, dirt etc., and a gel coat is

applied so that the laminate peels off from the surface easily

Calculated amount of Resin and proportionate hardner is mixed for application.

Mold surface is treated with realizing agent.

Fiber laminates are piled to required thickness one above the other by applying

resin mixture in between the laminates.

Mold surface is covered by sealant.

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A clean and flexible Cellophane plastic sheet is covered on laminates.

Bag is air tightened using sealant.

A vent is inserted through the bag to remove air using vacuum pump.

Suction of vacuum pump is connected to vent through a pipe.

Pump is switched on and the arrangement is kept undisturbed for about

20 minutes in room temperature.

After 20 minutes bag is removed and composite product is kept for post curing

operation for 2 hours at 100°C

Fig: 4.1 Representation of hand layup process

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Fig : 4.2 Vacuum bag molding.

4.6 Precuring:

The curing process transforms the resin into a plastic or rubber by cross-linking

process. The cross linking process forms a molecule with a larger molecular weight

resulting in a material with a higher melting point. During the reaction, when the

molecular weight has increased to a point so that the melting point is higher than the

surrounding ambient temperature, the material forms into a solid material. Room

temperature curing has been done with hardener added as initiator

4.7 Post curing:

Definition: The process of forming an uncured thermoset-ting resin article, then

completing the curing after the article has been removed from its forming mold or

mandrel. It has been found that time temperature of the post cure influences properties

composites.

After 20 minutes bag is removed and composite product is kept for post curing

operation for 2 hours at 100 °C in heating chamber.

4.8 Preparation of test specimens:

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Laminates thus obtained having the dimension 315mm*315mm.Specimens is

cut according to ASTM standards using switch board cutting blade.

4.9 CALCULATIONS:

For 60:40 composition:

1. Density of the laminate= Wt fraction of woven fabrics * density of woven

fabrics+ Wt. fraction of Resin * density of resin

= 0.6 *fabric density +0.4*density of resin

Here, we need to find the table value of the density of the fabrics and the resin

to be used in the fabrication. Weight fraction is the percentage of the resin and

the percentage of the fabrics

Fabric density is calculated as follows:

Fabric density = Weight fraction of glass fibre*density of glass fibre+ Weight

Fraction of PET * density of PET

= 0.66*2.6+0.34*1.37

= 2.1818g/cc

Density of Epoxy Resin ( LY 556) = 1.2g/cc

Density of the laminate = 0.6*2.1818+0.4*1.2

=1.80g/cc

2. Mass of the laminate = Density of the laminate * Volume of the

laminate

= 1.180 * 32 * 32 * 0.4

= 483.328 g

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Volume of the laminate is the product of the dimensions of the laminate. Here

32*32 is the area while 0.4is the thickness.

Ratio of Resin: Hardner

=100:10 (i,e10% of resin weight is hardener

weight)

Mass of the resin = mass of the laminate * Weight fraction of resin

= 483.328 * 0.4

=193.33 g

3. Mass of Hardener = 0.1*193.33

=19.3

4. Mass of Resin and Hardener = 212.663g

5. Mass of Woven fabric = mass of the laminate*weight fraction of Woven

fabrics

= 483.328 *0.6

= 289.99 g

Same as the calculation of mass of resin the laminate

6. No of plies = Mass of jute fabrics/mass of 1 ply

= 289.99/22.30

≈13 plies.

Before doing the fabrication : need to find the weight of one ply. And to find

the number of plies you need to divide mass of Woven fabrics by mass of 1

ply.

Amount of resin has to taken 15 to 20 grams more than the calculated amount as

there will always be some amount of resin will be remaining in bowl,loss while

applying and flow losses.

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CHAPTER 5

Experimental methods

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CHAPTER 5

EXPERIMENTAL METHODS

TESTS CARRIED.

5.1 Physical Properties

1. Surface Hardness

2. Specific Gravity and Density.

5.2 Mechanical Properties

1. Tensile strength

2. Flextural Strength

3. Short beam Strength (Inter Laminar Shear strength )

5.3 Thermal Properties

1.Heat Distortion Temperature (HDT)

2. Dynamic Mechanical Analysis (DMA)

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5.4 Non Destructive Evaluation.

1.Using Ultrasonic Measurement

5.5 PHYSICAL PROPERTIES

5.5.1 Density (ASTM D792, ISO 1183)

Figure 5.1 mass and density relationship

Scope:

Density is the mass per unit volume of a material. It is expressed in kg/m3.

Specific gravity is a measure of the ratio of mass of a given volume of material

at 23°C to the same volume of deionized water. Specific gravity and density are

especially relevant because plastic is sold on a cost per kg basis and a lower density or

specific gravity means more material per kg or varied part weight.

Significance and use

1.Specific gravity or density of a solid is a property that can be measured to identify

material to follow physical changes in a sample, to indicate degree of uniformity

among different sampling units.or to indicate average density of a large item.

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2.Density is useful calculating strength to weight and cost to weight ratio.

Equipment Used:

Mettler Balance

Fixture for weighing samples in water

Figure 5.2 Density testing apparatus

Test Procedure:

The specimen is weighed in air and then weighed when immersed in distilled

water at 23°C using a sinker and wire to hold the specimen completely submerged as

required. Density and Specific Gravity are calculated using the following data obtained

form the experiment.

Calculations:

Specific gravity = a / [(a + w)-b]

a = mass of specimen in air.

b = mass of specimen and sinker (if used) in water.

W = mass of totally immersed sinker if used and partially immersed wire.

Density, kg/m3 = (specific gravity) x (1000)

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5.5.2 Hardness Test (SHORE-D)(ASTM D 2240-86)

Aim:

The aim of this experiment is to find out the SHORE D (ASTM D2240)

hardness number of the composite laminate.

Theory:

The Metals Handbook defines hardness as "Resistance of metal to

plastic deformation, usually by indentation. However, the term may also refer to

stiffness or temper or to resistance to scratching, abrasion, or cutting. It is the

property of a metal, which gives it the ability to resist being permanently,

deformed (bent, broken, or have its shape changed), when a load is applied. The

greater the hardness of the metal, the greater resistance it has to deformation.

Fig.5.3. Shore D hardness testing machine.

Shore Hardness, using either the Shore A or Shore D scale, is the preferred

method for rubbers/elastomers and is also commonly used for 'softer' plastics such as

polyolefins, fluoropolymers, and vinyls. The Shore A scale is used for 'softer' rubbers

while the Shore D scale is used for 'harder' ones. The shore A Hardness is the relative

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hardness of elastic materials such as rubber or soft plastics can be determined with an

instrument called a Shore A durometer. If the indenter completely penetrates the

sample, a reading of 0 is obtained, and if no penetration occurs, a reading of 100

results. The reading is dimensionless.

The Shore hardness is measured with an apparatus known as a Durometer and

consequently is also known as 'Durometer hardness'. The hardness value is determined

by the penetration of the Durometer indenter foot into the sample. Because of the

resilience of rubbers and plastics, the hardness reading my change over time - so the

indentation time is sometimes reported along with the hardness number. The ASTM

test number is ASTM D2240 while the analogous ISO test method is ISO 868.

Test Procedure:

The specimen with a minimum thickness of 4mm is placed on a flat horizontal

surface. An excessively coarse surface will yield low and erratic readings.

Small specimen is clamped securely to test the surface perpendicular to the

indentor axis.

The indentor for the instrument is then pressed into the specimen making sure

that it is parallel to the surface.

The hardness is read within three seconds of firm contact with the specimen.

The Shore D hardness number is directly derived from scale.

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5.6 Mechanical Properties

5.6.1 Tensile properties of composite (ASTM D3039)

Aim:

To determine tensile properties such as tensile strength and tensile modulus of

composite.

Significance and use:

This test method is designed to produce tensile property data for control and

specification of composite materials. These data are useful for qualitative

characterization, engineering design and R&D purposes.

Apparatus:

1.Tensile testing machine or UTM, of constant rate of grip separation type

comprising of fixed member, movable member, grips, drive mechanisms, load and

extension indicators.

2. Plotter and micrometer.

Fig5.4. Universal Testing Machine

Specimen size:

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The test specimen dimensions for reinforced composites, including high

modulus orthographic laminates shall conform to the dimensions of Type 1. The

specimen dimension taken is 175*10*3.2. (Where 10refers to width of narrow section)

Procedure:

Measure the width and thickness of specimens with a suitable micrometer to the

nearest 0.02 mm at several points along their narrow sections within the gauge

boundaries. Record the minimum value of cross sectional area so determined.

Mark gauge length on the specimen.

Set the grip separation speed of the machine; place the specimen straightly in

the grips.

Tighten the grips evenly and firmly to the extent necessary to prevent slippage

of the specimen during test and not to the point where the specimen would be

crushed.

Start the machine and record the load extension curve.

Record the load and extension at yield and break point.

Formula used

1. Tensile strength =Max load / Cross sectional area. N/mm²

2. Strain = Change in length (mm) / Original (gauge) length (mm)

3. Young’s modulus (modulus of elasticity) (N/mm²) = Stress/Strain

5.6.2 Flexural test (3-point bending) (ASTM 790 -86)

Aim:

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To determine the flexural strength and flexural modulus using three point bending

test.


This test generates the characteristics of a material in bending, which is useful in

designing of structural parts.

Apparatus:

Flexural testing machine or UTM, of constant rate of grip separation type


extension indicators.

Fig5.5. Universal Testing Machine

Procedure:

Turn on the system and perform the start-up calibrations.

Prepare the system for the testing method,3-point bending.

Install the 3-point bend fixture.

Install the sample, taking care to align it correctly.

Lower the crosshead to where it almost touches the sample.

Start the automated test procedure.

Carefully watch the sample for the first cracks to form, and monitor the loads

and the load-elongation graph.

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Stop the test after the samples fail completely or before the fractured sample

touches the base of the 3-point bend fixture.

Sample (127mm×12.7mm×3.2mm) Force

100mm

Fig5.6. Schematic representation of 3-point bending fixture

Formula used

FLEXURAL STRENGTH=3Pl/2bd² . N/mm²

Where,

P=Breaking load, N

l=Span length, mm

d=Depth, mm

b=Width, mm

Flexural Modulus=l³ y/4bd³ N/mm²

Where,

y=slope of the tangent of the initial straight line portion of the load deformation curve.

= dy/dx

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5.6.3 Short Beam Strength of Laminates Or Inter Laminar

Shear Strength (ASTM D2344/D2344M)

Aim:

To determine the Short beam Strength of high modulus fiber reinforced

composite materials


Short Beam Shear is used to determine interlaminar shear strength of parallel fibers. It

is applicable to all types of parallel fiber reinforced plastics and composites. The data can be

used for research and development purposes concerned with interply strength, or prove useful

in comparing composite materials.

Apparatus:

Universal testing Machine (UTM), of constant rate of grip separation type


extension indicators and Flex Fixture with Short Beam Shear Heads.

Specimen Size:

The test specimens are machined from flat, finished composites.

The following dimensions are recommended :

Specimen length = thickness * 6.0

Specimen width = thickness*2.0

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Fig5.7. Inter Laminar Shear Strength testing machine

Procedure:

The thickness and width of the test specimen are measured before conditioning. The

specimen is placed on a horizontal shear test fixture so that the fibers are parallel to the loading

nose. The loading nose is then used to flex the specimen at a speed of .05 inches per minute

until breakage. The force is then recorded. Calculations are performed to determine shear

strength.

Formula used ShearStrength = 0.75xbreakingload

width x thickness.

5.7 THERMAL PROPERTIES

5.7.1 HEAT DISTORTION TEMPERATURE (HDT) OR

DEFLECTION TEMPERATURE UNDER LOAD (DTUL) (ASTM

D648-82)

Scope:

”Heat distortion temperature is defined as the temperature at which a standard test bar

deflects a specified distance under a load”. It is used to determine short-term heat resistance. It

distinguishes between materials that are able to sustain light loads at high temperatures and

those that lose their rigidity over a narrow temperature range.

Equipment Used:

HDT tester,

Immersion Bath

Heat transfer liquid

Deflection measurement device

Thermometer

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Weights

Figure 5.8 Heat deflection temperature test apparatus

Specimen size: A standard bar 127*13.5*3.2 is used for ASTM

Test Procedure:

The bars are placed under the deflection measuring device. A load of 0.45 MPa

or 1.80 MPa is placed on each specimen. The specimens are then lowered into a

silicone oil bath where the temperature is raised at 2° C per minute until they deflect

0.25 mm for ASTM, 0.32 mm for ISO flat wise, and 0.34 mm for ISO edgewise. The

temperature at the specified load and deflection is given.

5.7.2 DYNAMIC MECHANICAL ANALYSIS (DMA) TEST:

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DMA:

Dynamic Mechanical Analysis, otherwise known as DMA, is a technique where a

small deformation is applied to a sample in a cyclic manner. This allows the materials

response to stress, temperature, frequency and other values to be studied. The term is

also used to the analyzer that performs the test. DMA is also called DMTA for

Dynamic Mechanical Thermal Analysis.

Scope:

The viscoelastic nature of polymers is well known and is unique in the field of

material properties. The term is used to describe the time-dependent mechanical

properties of polymers, which in limiting cases can behave either as elastic solids or as

viscous fluids. Knowledge of the viscoelastic behavior of polymers and its relation to

molecular structure is essential to an understanding of both processing and end-use

properties.

The time-dependent changes in polymers subjected to constant stress(creep) or

constant strain (stress relaxation) give insight into viscoelastic behavior, but more

information can be obtained, often on a more convenient time scale, by the study of

dynamic mechanical properties. Here the response (stress) in a material subjected to a

periodic stimulate (strain) is measured. Generally, the applied deformation and the

resulting stress both vary sinusoidally with time . Dynamic experiments yield both the

elastic modulus of the material and its mechanical damping or energy dissipation,

characteristics. The properties can easily be determined as functions of frequently

(time) and temperature

Measurement:

DMA measures the following:

1. Both displacement and force are measured by amplitude and phase shift.

2. Complex modulus, compliance (inverse of modulus) and tan delta is calculated.

3. The sample is excited with a sinusoidal force (stressed).

Parameters:

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Force

Frequency

Temperature

Sample holder (shear, bending, tension)

Sample geometry (dimensions)

As described earlier, If the material is 100% elastic (energy stored) then phase shift=0.

If the materials is 100% viscous (energy loss) then phase shift= 900. If viscoelastic then

0< >900.

Fig 5.9 Dynamic mechanical analyser

Typical DMA Components:

Drive motor - supplies energy

Suspension - allow system to move

Drive shaft – supplies energy to sample

Clamps – hold sample in place

Positive/displacement detector – measures motion

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Force sensor – measures force supplied to sample

Furnace – controls temperature

Key Design Features of Typical DMA:

Force is measured by measuring voltage/current delivered to drive motor

Displacement sensor on drive shaft near motor

Minimize suspension restoring force to lower baseline force to sample

Alignment of sample depends on clamp installation – clamps are fixed in place

Specimen size:

The specimens are typically 56mm in length, 13mm in width and 3mm in thickness.

5.8 Non destructive Evaluation of Laminates

Significance and Use.

This practice is intended primarily for the testing of flat panel composites and

sandwich core panels to an acceptance criteria most typically specified in a purchase

order or other contractual document.

Like any other materials composites are prone to defects which drastically

degrade the materials properties. Therefore, to make sure that defects of composites

should be tested both prior and during the life of the component .De-lamination is an

important problem in the application of FRP Composites.

Apparatus and Description of Procedure

QMI Inc., USA make air-coupled ultrasonic test equipment was used in the

present study. Planar / focused narrow-band piezoelectric air-coupled ultrasonic

transducer probes with center frequencies of 120 kHz and 400 kHz were used for the

measurements. These transducers were driven by their matching electronics provided

by the SONDA 007CX pulsar and receiver system. The dimensions of the piezoceramic

elements ranged from 3/4" to 1" diameter. The settings were maintained at 60 dB gain /

62 dB and 40 dB gain / 60.9 dB attenuation for ultra sonic frequencies of 120 and 400

kHz respectively.

Hybrid Composite

The mean transmission (as obtained from inbuilt WINSPECT Software) of

ultrasonic waves through glass fiber-PET composites scanned at 120 and 400 Hz

frequencies has to record. The percentage transmission can be read from the colour

index given separately for each of the frequencies.

Hybrid Composite

CHAPTER 6

RESULTS AND DISCUSSIONS

Hybrid Composite

CHAPTER 6

RESULTS AND DISCUSSIONS

6.1 DENSITY TEST RESULTS

Sample Specific Gravity Avg. Specific

Gravity

65:35

1.881

1.853

1.846

1.832

60:40

1.73

1.802

1.721

1.741

50:50

1.712

1.730

1.802

1.892

Table 6.1 Density test results

Hybrid Composite

Figure 6.1 Density Vs. Percentage of Resin content

The Specific Gravity and density of Laminates along with percentage of fiber is

shown in the table .The density values are in the range of 1.7 to 1.9. It can be

concluded that as the amount of fiber increases density is found increasing, this is

credited to high dense ,high modulus glass fiber.

6.2 Surface Hardness ( ASTM 2240-86)

Hybrid Composite

Hardness test (shore-D)

Sample 1 2 3 4 5 Average

50:50 75 74 70 73 75 73.4

60:40 78 75 77 72 74 75.2

65:35 75 75 78 80 70 75.6

Table 6.2 Hardness( Shore D) of Different Laminates

Figure 6.2.1 Density Vs. Percentage of Resin content

The Surface Hardness of Laminates along with percentage of fiber is shown in

the table .The density values are in the range of 70 to 80 . It can be noticed that

surface hardness values of composites are less or more nearly same, the high value is

noticed at higher fiber volume(65:35) due to rigid Glass-PET reinforcement .

6.3 TENSILE TEST

TENSILE TEST RESULTS FOR Fiber:Resin ratio of 65-35

Hybrid Composite

Sample 1 2 3

Gauge Length (mm) 50 50 50

Width (mm) 9.05 9.12 9.15

Thickness (mm) 4.136 4.221 4.12

Area (mm²) 37.4308 38.49 37.69

Speed(mm/min) 4.5 4.5 4.5

Maximum Load(N) 4321.01 4214.655 4354.32

Deflection at Maximum

Load mm1.245 1.335 1.26

Stress at Maximum

Load (MPa)115.44 109.5 115.53

Percentage Strain at

Max. loadMaximum

Load

2.49 2.67 2.52

Tensile Modulus (MPa) 5840 5860 7670

Table 6.2.1Tensile test result of composite specimens with different Fiber

percentage

TENSILE TEST RESULTS FOR Fiber:Resin ratio of60:40

Sample 1 2 3

Hybrid Composite


Width (mm) 10.28 10.24 10.21

Thickness (mm) 4.55 4.63 4.56

Area (mm²) 46.774 47.411 46.557


Maximum Load(kN) 11617.726 12582.40 13710.570

Deflection at

Maximum Load (mm)1.435 1.33 0.725

StressMaximum Load

(MPa)

248.38 265.39 294.49


Max. loadMaximum

Load

2.87 2.66 1.45

Tensile Modulus

(MPa)5430 6140 8420

Table 6.2.2 Tensile test result of composite specimens with different Fiber percentage

TENSILE TEST RESULTS FOR Fiber:Resin ratio of 50:50

Sample 1 2 3


Width (mm) 9.05 9.12 9.15

Hybrid Composite

Thickness (mm) 4.136 4.221 4.12

Area (mm²) 37.4308 38.49 37.69


Maximum

Load(kN)

3178.18 3247.4 2718.956

Deflection at

MaximumLoad mm 1.245 1.335 1.26

StressMaximum

Load (MPa)

84.91 84.37 72.14


Max.

loadMaximum Load

2.49 2.67 2.52

Young's Modulus

(MPa)5840 5860 7670

Table 6.2.3Tensile test result of composite specimens with different Fiber

percentage

Hybrid Composite

Fig 6.3.1Youngs Modulus vs % of Resin

Fig 6.3.2 Tensile Strength vs Percentage of Resin

6.4 Flextural Test

Specimen 1 2 3

Hybrid Composite

Depth d (mm) 4.1 4.16 4.1

Width b (mm) 12.7 13.22 13.05

Support span length L

(mm)

63 63 63

Rate of cross head motion

(mm/min)

1.6 1.6 1.6

Maximum Load at break

(KN)260.024 224.18 220.763

Max Deflection at break

(mm)

8.067 7.95 8.067

Flexural Strength (MPa) 115.1 92.6 95.1

Flexural Modulus(GPa) 5.89 5.25 5.07

Strain 0.0499 0.0499 0.0499

Table 6.4.1 Flexural test results for 65:35 specimen

Specimen 1 2 3

Hybrid Composite

Depth d (mm) 3.61 3.80 3.84

Width b (mm) 12.7 12.9 13.3


(mm)

63 63 63


(mm/min)

4.5 4.5 4.5


(N)606.68 602.58 696.26


(mm)

9.162 8.703 8.613



Strain 0.0499 0.0499 0.0499


Hybrid Composite

Specimen 1 2 3

Depth d (mm) 4.95 4.39 4.42

Width b (mm) 12.8 13.0 13.2


(mm)

63 63 63


(mm/min)

4.5 4.5 4.5


(N)276.46 504.25 404.96


(mm)

6.68 7.534 7.483



Strain .0499 .0499 .0499


Hybrid Composite

Fig 6.4.1 Flexural Strength vs. Percentage of Resin

Fig 6.4.2 Flexural Modulus vs. Percentage of Resin

6.5 Short Beam Strength (D2344/D2344M)

Hybrid Composite

Sample Short Beam

Strength in Mpa

Mean Value of

Short Beam

Strength (MPa)

65:35

15.15

14.16

16.39

10.95

60:40

23.60

24.55

23.47

26.59

50:50

19.81

18.72

19.07

17.27

Fig 6.5.1 Short Beam Strength vs. Percentage of fiber

6.6 Discussion on Mechanical Properties

Hybrid Composite

The tensile properties of GF composite are controlled byfiber volume fraction,

fiber aspect ratio, fiber strength , fiber alignment and distribution and interfacial

adhesion between fiber and matrix.

From the three compositions of fiber(50%,60%,65%), 60% of fiber

composition exhibits excellent high tensile strength of 294.49Mpa and modulus

of 16.23Gpa due to uniformity in distribution of resin.

As the fiber content is more(65:35)the fibers do not effectively reinforce the

matrix and as Resin content increases (50:50)there will not be enough fiber to

bear the load and hence strength is less.

Glass-PET Epoxy laminates exhibits high modulus which indicates capability of

material in high modulus applications.

The Measured Values of Flextural strength and Flextural Modulus are shown in

the table which surprisingly shown highest properties at 40% of the fiber

compositions. The short beam strength also shows the same results.

6.7 HEAT DEFLECTION TEMPERATURE (HDT) TEST RESULT

Hybrid Composite

Table 6.7 Heat deflection temperature test results

Fig.6.7. Heat deflection temperature vs. Percentage of Resin

The heat deflection temperatures of hybrid composites are determined and the obtained

results are given in table. The HDT values of hybrid GF-PET composites lie in the

range of 116 to 125 degrees. And it is found Maximum at 60:40 Fiber: Resin

composition.

6.8 DYNAMIC MECHANICAL ANALYSER(DMA) TEST RESULTS

Heat Deflection temperature

Sample

Deflection temperature at

1820Kpa

(oC)

65:35 118

60:40 124

50:50 116

Hybrid Composite

LAMINATE

COMPOSITION

GLASS TRANSITION

TEMPERATURE ( Tg )

in 0 c

TAN δ

(LossModulus/Storage

modulus)65:35 103.5 0.1096

60:40 103.5 0.136

50:50 103.5 0.129

Table 6.8.1 : GLASS TRANSITION AND TAN DELTA VALUES FOR DIFFERENT

COMPOSITIONS.

LAMINATECOMPOSITION STORAGE MODULUS in Mpa

65:35 3100

60:40 6400

50:50 4450

Table 6.8.2: Values of Storage Modulus For Different Composition.

Hybrid Composite

0

2000

4000

6000

8000

Sto

rag

e M

od

ulu

s (M

Pa

)

20 40 60 80 100 120 140 160 180

Temperature (°C)

65-35.001––––––– 60-40.001––––––– 50-50.002–––––––

Universal V4.3A TA Instruments

Fig. 6.8.3 Comparison of Storage Modulus Vs temperature for Different

compositions

Storage modulus which is a measure of stiffness of a material will increases as

the Fiber percentage in the hybrid composite is increased and optimum at 40% .

But beyond if the Fiber percentage (i.e for 65%) storage modulus will decrease.

Glass transition temperature of composite material will vary slightly as Fiber

percentage is varied.

TAN δ measure of damping property of composite material is found to be

maximum 60% fiber by weight. The comparative graphs are shown in next chapter.

6.9 RESULTS AND DISCUSSIONS OF NON DESTRUCTIVE

EVALUATION

Hybrid Composite

In the recent past, air-coupled ultrasonic C-scanning is increasingly being used

by research workers in the field of non-destructive evaluation (NDE). The advantage of

this technique is that it does not rely on any external couplant media (liquids, gels,

pastes etc.). The use of lower frequencies employed in this new method ensures

improved transmission characteristics of the ultrasound through materials, especially

for foams and composites.

Table shows the mean transmission (as obtained from inbuilt WINSPECT

Software) of ultrasonic waves through glass fiber-PET composites scanned at 120 and

400 Hz frequencies. The percentage transmission can be read from the colour index

given separately for each of the frequencies.

Table 6.9 NDT transmission data of glass fibre-PET laminates

Sample Transmission (%)

120 Hz 400 Hz

65:35 Laminate with 13 layers of

hybrid fabric thickness, 4.17 mm

55 60


hybrid fabric thickness, 3.6260 62


hybrid fabric , thickness 4.54 mm

47 55

The mean transmission through the samples increased with increase in

frequency in both the samples. It is also observed that sample with more thickness

exhibits slightly less uniformity in the distribution of resin and may be due to the skin

core effect behavior generally observed in thicker laminates. The mean transmission of

samples with less number of layers (thickness 3.3 mm) exhibited very high values

suggesting that the laminates are not much influenced by the attenuation of the waves.

Hybrid Composite

The mean transmission through the samples increased at higher frequency (400 kHz)

possibly due to the different variable gain used in the case of 120 and 400 Hz

frequencies. The other reason for the above behaviour may the effect of resolution

capability and the effective interaction with the materials at a particular frequency.

CHAPTER 7

Hybrid Composite

GRAPHS OF VARIOUS RESULTS

7.1 .1Tensile Test ( Stress- Strsin Graphs of 3 samples of

50% Fiber)

Hybrid Composite

Fig7.1.1 stress vs strain curve for 50:50

Hybrid Composite

7.1.2 Tensile Test ( Stress- Strain Graphs of 3 samples of

60% Fiber)



Hybrid Composite

7.1.3 Tensile Test ( Stress- Strsin Graphs of 3 samples of

65% Fiber)


7.2.1 Dynamic Mechanical Analysis ( F:R of 50:50)

Hybrid Composite

0

1000

2000

3000

4000

5000S

tora

ge

Mo

du

lus (

MP

a)

20 40 60 80 100 120 140 160 180

Temperature (°C)

Sample: 50-50Size: 35.0000 x 13.5000 x 4.0500 mmMethod: Temperature Ramp

DMAFile: D:\VB\50-50.002Operator: SHKRun Date: 05-Jun-2010 12:33Instrument: DMA Q800 V7.4 Build 126


Fig 7.2.1 Storage Modulus vs. Tempreature

0

200

400

600

Loss M

odulu

s (

MP

a)

20 40 60 80 100 120 140 160 180

Temperature (°C)




Fig 7.2.2 Loss modulus vs. Tempreture

Hybrid Composite

101.03°C

0.0

0.2

0.4

0.6

Ta

n D

elta

20 40 60 80 100 120 140 160 180

Temperature (°C)




Fig 7.2.3 Tandelta vs Tempreature

0.2

0.4

Ta

n D

elta

0

200

400

600

Lo

ss M

od

ulu

s (

MP

a)

0

1000

2000

3000

4000

5000

Sto

rag

e M

od

ulu

s (

MP

a)

20 40 60 80 100 120 140 160 180

Temperature (°C)




Fig 7.2.4 Overlay of Shear Modulus , Loss Modulus and tan delta

Hybrid Composite


0

2000

4000

6000

8000

Sto

rage M

odulu

s (

MP

a)

20 40 60 80 100 120 140 160

Temperature (°C)

Sample: 60-40 repeatSize: 35.0000 x 13.4000 x 3.4000 mmMethod: Temperature Ramp

DMAFile: D:\VB\60-40 repeat.001Operator: SHKRun Date: 05-Jun-2010 11:27Instrument: DMA Q800 V7.4 Build 126


Fig.7.2.5 Storage Modulus vs. Tempreature

0

200

400

600

800

1000

Loss

Modulu

s (M

Pa)

20 40 60 80 100 120 140 160

Temperature (°C)


DMAFile: D:\VB\60-40 repeat.001Operator: SHKRun Date: 05-Jun-2010 11:27Instrument: DMA Q800 V7.4 Build 126


Fig.7.2.6 Loss Modulus vs. Tempreature

Hybrid Composite

106.56°C

0.0

0.1

0.2

0.3

0.4

Ta

n D

elta

20 40 60 80 100 120 140 160

Temperature (°C)




Fig. 7.2.7 Tan Delta vs. Tempreature

0.1

0.2

0.3

Ta

n D

elta

0

200

400

600

800

1000

Lo

ss M

odu

lus (

MP

a)

0

2000

4000

6000

8000

Sto

rag

e M

od

ulu

s (

MP

a)

20 40 60 80 100 120 140 160

Temperature (°C)





Hybrid Composite


0

1000

2000

3000

4000

Sto

rage M

odulu

s (

MP

a)

20 40 60 80 100 120 140 160

Temperature (°C)




Fig.7.2.9 Storage Modulus vs. Tempreature

Hybrid Composite

0

100

200

300

400

Lo

ss M

od

ulu

s (M

Pa

)

20 40 60 80 100 120 140 160

Temperature (°C)




Fig.7.2.10 Loss Modulus vs. Tempreatur

107.63°C

0.0

0.1

0.2

0.3

0.4

Ta

n D

elta

20 40 60 80 100 120 140 160

Temperature (°C)




Fig.7.2.11 Tan Delta vs. Tempreature

Hybrid Composite

0.1

0.2

0.3

Tan

Del

ta

0

100

200

300

400

Loss

Mod

ulus

(MP

a)

0

1000

2000

3000

4000

Sto

rage

Mod

ulus

(MP

a)

20 40 60 80 100 120 140 160

Temperature (°C)





0

2000

4000

6000

8000

Sto

rag

e M

od

ulu

s (M

Pa

)

20 40 60 80 100 120 140 160 180

Temperature (°C)

65-35.001––––––– 60-40.001––––––– 50-50.002–––––––


Hybrid Composite

Fig 7.2.13 Comparision of Storage Modulus at various fiber Proportions

0

200

400

600

800

1000

Lo

ss M

od

ulu

s (M

Pa

)

20 40 60 80 100 120 140 160 180

Temperature (°C)

65-35.001––––––– 60-40.001––––––– 50-50.002–––––––


Fig 7.2.14 Comparision of Loss Modulus at various fiber Proportions

107.63°C

106.56°C

101.03°C

0.0

0.2

0.4

0.6

Ta

n D

elta

20 40 60 80 100 120 140 160 180

Temperature (°C)

65-35.001––––––– 60-40.001––––––– 50-50.002–––––––


Fig 7.2.15 Comparison of Tan delta at various fiber Proportions.

Hybrid Composite

7.3 NON DESTRUCTIVE TESTING

Fig7.3.1 Scanned images of NDT at 120 khz

Non Destructive Evaluation of Laminates at 120 Khz frequency

Test Parameters : 120khz , 60db attenuation , 54db gain and : 400khz , 40db

attenuation , 55db gain

Fig7.3.2 Scanned images of NDT at 400 khz

Hybrid Composite

Non Destructive Evaluation of Laminates at 400 Khz frequency

Test Parameters : 400khz , 60db attenuation , 55db gain and : 400khz , 40db

attenuation , 55db gain

CHAPTER 8

CONCLUSIONS

Hybrid Composite

CHAPTER 8

CONCLUSIONS

The PET fiber can be reinforced to exhibit high Mechanical properties and can

be effectively combined with reinforcing materials like Glass (Saline treated).

The properties of the composite ultimately depend on Fiber to Resin proportion.

The increase in percentage of fiber provides good mechanical & thermal

properties.

This can supported by Non Destructive Evaluation using ultrasonic C-scan

technique, which shows good transmission especially at 40% resin blend.

Considering the DMA test results, it is applicable for structural application with

a service temperature of up to 160°C

Structural application in building Naval and Light combat Aircraft &

Aerospace.

Summarizing the system design based on Glass-PET hybrid composites

exhibit superior properties, particularly for 60:40 to what is achievable in

thermosetting resin system counterparts.

Hybrid Composite

Bibliography

“Composites manufacturing” Materials, product and process .Sanjay K

Mazumdar.

Design and manufacturing of textile composites. A C Long.

Composite materials science and engineering. Krishn Kumar Chawla

Mechanics and analysis of composite materials. By Valery V.Vasiliev and

Evgeny V.Morozov.

ASTM Standard hand book for plastics volume 1

ASTM Standard hand book for plastics volume 2

Websites:

www.springer.com

www.sciencediect.com

www.elsecier.com

http://en.wikipedia.org/wiki/Composite_material

http://info.lu.farmingdale.edu/depts/met/met205/composites.html

http://composite.about.com/

http://www.pcb007.com/pages/zone.cgi?a=48383&_pf_=1

http://www.fibersource.com/f-tutor/polyester.htm

http://en.wikipedia.org/wiki/Polyethylene_terephthalate

http://en.wikipedia.org/wiki/Fiberglass

http://en.wikipedia.org/wiki/Epoxy

http://dir.indiamart.com/impcat/epoxy-hardeners.html

http://www.ptli.com/testlopedia/tests/dma-d4440.asp

http://www.ptli.com/testlopedia/tests/dma-d4440.asp

http://dir.indiamart.com/impcat/epoxy-hardeners.html

http://en.wikipedia.org/wiki/Epoxy

http://en.wikipedia.org/wiki/Fiberglass

http://en.wikipedia.org/wiki/Polyethylene_terephthalate

http://www.fibersource.com/f-tutor/polyester.htm

http://www.pcb007.com/pages/zone.cgi?a=48383&_pf_=1

http://composite.about.com/

http://info.lu.farmingdale.edu/depts/met/met205/composites.html

http://en.wikipedia.org/wiki/Composite_material

http://www.elsecier.com/

http://www.sciencediect.com/

http://www.springer.com/

Hybrid Composite

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