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INTRODUCTION

Composite materials are considered the most advanced

and adaptable engineering materials known to man.

A composite material is the combination of 2 or more

distinct materials into one engineering material where

the phases are still significantThe word composite is derived from the latin word

componere which means to put together .

The components are put together in order to suppress

their undesirable properties in favor of their desirable

properties.

This does not include metal alloys or polymer blends

which combines at an atomic level.

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Evolution of Material

During the stone age, flint was used as cutting material.Metals were then least important.

At that time, natural polymers (wood, skins, fibers) dominated

in the engineering applications. (house, weapons, boats)

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Later, metal working evolved and development dominatesengineering achievement until into 20th century.

In 1960s the use of metal in engineering material declined.Polymers, composites and ceramics regaining the relativeimportance to man. However these are synthetic materials.

Examples of natural composites are trees, wood, bone ormollusk shell. Natural composites tend to be weaker and lessstiff than synthetic composites, but are often superior in termsof design and manufacture. E.g: Spider Web

Natural composites are also smart materials in that theyadapt to the environment.

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Synthetic composites- first composites are

believed to be made by the Egyptians who used

straw to reinforce clay to make brick.

They use papyrus reeds (placed parallel to each

other forming layers, and then stacked

perpendicular to each other in alternate directions,

dried under pressure to form paper like sheets.

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-Composites in most cases comprisesof a bulk phase enclosing a fibrousreinforcing phase; called matrix andreinforcement.

Matrix

Gives shape to the composites

Bind the reinforcement together

Introduce external loads to the

reinforcement Protect it from environmental effects(hightemperature, water, UV light, etc)

Fiber Reinforcement

Carries, the structural loads Dictates microscopic stiffness & strength

The Composite Concept

Fiber reinforcement

Matrix

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BASIC KNOWLEDGE Most impressive mechanical properties are found in composites with

continuous and aligned reinforcement.

Why polymer composites are used in most structural applications?

-they offer a given property

-often excellent stiffness and strength at a lower weight than the competition(steel, concrete, wood).

Properties of composite materials:

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Properties of Polymer Composites

Advantages Disadvantages

- corrosion resistance - high raw material cost

- electrical insulation - difficult manufacturing

- reduction in tool and assembly cost - lack of knowledge/experience

- decrease in maintenance cost

- exceptional formability

Composites are therefore certainly not appropriate in

all applications;

a critical assessment of the material alternativesmust always be made in term ofperformance- cost

ratio.

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Transport Applications Is a dominant sector of

composites and the fastestgrowing.

High specific stiffness andstrength but lighter parts can

be exploited to reduce fuelconsumption or to increasepayload. (commercialvehicles)

Better feasible mold designgeometrically can beachieved by usingcomposites

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In some truck and bus

applications, usually body panels

and dashboards are designed

from composites.

Composites also turn up in an

increasing number of non-

structural or semi- structuralunder the hood applications,

where temperatures are of the

order of 150oC or higher.

More applications such as noiseshields, heat shields, air intake

manifold, engine top cover etc.

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In F1 and motorcycle racing,they use composites:

-save weight and thus gainperformance.

Carbon fiber and Kevlar arebeing used as they arelightweight, high in strength

with good heat resistance.

Body parts of sports cars aredesigned as composite bodypanel fastened to a

conventional steel spaceframe like dodge viper,skyline and the newMercedes CLK.

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Boat Building

By the 1950's, boat buildersbegan the transition to fiberglasshulls. Such designs are:

-easier to build

-significantly lower in cost

-complex shapes were easily formedin fiberglass when compared towood or metal.

Buyers got attractive new stylesthat were lower cost, easier totransport, extremely durable andeasy to maintain, since fiberglassdoes not rust like steel nor rot likewood.

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In the Defense world, marinecomposites offer similaradvantages.

Steel ships rust, requiringconstant maintenance.

The heavy weight of steelships also places limits on theirspeed and increases fuelconsumption: heavy ships takea lot of fuel to move. Becausewarships often have to worryabout explosive mines, themagnetic signature of ships is

a concern to all sailors.

Composites are non-magneticand make an ideal material forany ship expected to face minewarfare conditions. (MCMV)

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Aerospace and MilitaryApplications

The main reason to use composites:

-high profile material is needed

-the ultimate in performance

-saved weight is seen as increase inload carrying capability or a matter oflife and death.

The less insignificant fact is thatcomposites can lower manufacturingcost, better fatigue resistance thanlight metal.

Recently, glass reinforcedcomposites have been used inaircraft radomes (nose cones) andstealth properties (although most ofthe stealth technique depends on theangular geometry to reflect minimumof radiation).

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In commercial and civilian

aircraft applications,

potential weight saving is

highly valued.

Here, the use of carbon

reinforced epoxy sandwich

with honeycomb core as areplacement of metal rudder,

clearly resulted in a

reduction of 22 percent

weight and number of partsfrom 17000 to 4800 (since

bonding eliminates rivets)

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In aerospace, weightreduction by usingcomposites can be seenclearly from the launch of

The Pegasus XL, where analmost composite completestructure can be seen.

Composites are well suitedto applications where

primary load case is(internal) pressure.

For launching, manycomponents are exposed tosuch high temperatures

where compositescontaining ceramic andcarbon matrices are used.

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Construction Applications

Composites inconstruction come underindustrial and agriculturalequipment and corrosionresistant equipment.

The most significantexample of application isthe bridge building. The

Aberfeldy footbridge inScotland utilizes smallamount of heavymachinery and concrete.

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- In other industries such as

chemical plants, waste water

treatment plants,

composites are used in

construction applications

such as handrails, watertanks and silos to eliminate

corrosion issues and reduce

maintenance costs in

replacing steel components.

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Electrical and Sanitary Applications

In electrical applications, dielectricstrength of the glass-reinforcedcomposites is more important thanthe structural capabilities.

This includes circuit boards,equipment housings, transformerspacers and cable trays.

Ladder rail is a common example

where direct electrical contactbetween electrician and potentiallyhot wires and ground is obvious.

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- In sanitary applications suchas shower enclosures, bathtubs, spas, sinks and cabinets

composites are used as theypossess design freedom andeconomically proven on theproduction and maintenanceconsiderations.

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Sports Applications

In some applications whereperformance and weight isthe deciding factor, it is vitalto use composites to enhance

the properties

In ski, tennis, golf and squashapplications, the use of

Kevlar, graphite or carbonreinforcement is vital as theyactually change the traditionalapproach of the game aswell.

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Other Applications

The first one is medicine, wherecomposites for quite some time havebeen used in patient support tables inX-ray machines. These tables offergreat stiffness while still beingtransparent to the radiation in order notto obscure the radiograph.

- Composites are also beinginvestigated for artificial joints toreplace the more conventional metalcomponents used in, for example,artificial hip joints.

- A problem with inserting a titanium hipimplant into the femur is that thestiffness of the implant is so muchgreater than that of the bone, whichgradually leads to bone deterioration.

- With composites the stiffness can betailored to that of the bone to eliminate

this problem.

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A somewhat unusual composite application is in musical

instrument where string instruments so far have receivedthe most attention.

With careful design and manufacture an acoustic guitar,or for that matter any string instrument, can be made tosatisfy the pickiest musician.

Advantages:

-possibility of tailoring the instrument to whatever the

customer wants-the instrument is not sensitive to climate changes ortransportation damage

-no rare woods on the brink extinction are used.

Other Usage

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