seminar on composite materials

8/13/2019 Seminar On Composite Materials

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Introduction of Composite Materials

The word ‘Composite’ means consisting of two or more distinct parts’.Thus a material having two or more different constituent materials withsignificantly different physical or chemical properties is termed as CompositeMaterial.

Most of the composites are made of the two materials. One is the matrixor binder. It surrounds and binds together fibers or fragments of the other

material, which is called the reinforcement.


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By choosing an appropriate combination of matrix and reinforcement

material, a new material can be made that exactly meets the requirementsof a particular application.

The biggest advantage of modern composite materials is that they arelight as well as strong.

Composites also provide design flexibility because many of them can be

moulded into complex shapes.


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4) Cost: Cost of the manufacturing a composite material is quite high right

now but as the trend of composite material is setting up into industry, thecost is certainly going to economical in near future.

5) High Specific Modulus: Specific modulus may be defined as ratio of Young's Modulus (E) and density (p).The specific modulus is high for composite material which means the rodcross section made of composite material could only be one third of steel

of same strength. This reduction in cross sectional area and mass translatesto reduced space requirements an lower energy and material costs.


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Applications of Composite Materials

1) Automobile Parts: Composites being light weight and having highstrength capabilities it improves the performance of the vehicle.


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2) Aircrafts: Having high specific strength and lower radar signature,composite materials make around 50% contribution of total aircraft body.

Use of composites has known to make aircraft structures 25 % stronger thanconventional airframe aluminum but also 20 % lighter.


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3) Space & Satellite Applications: Due to low weight and low thermalexpansion characteristics of advanced composites, they are be used to

significant advantage in space and satellite systems.


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4) Defense Industry Applications: Composites are also used for thebulletproof jackets. The performs used for these applications are very tightly

wounded and covered with resin so that they can absorb great amount ofimpact force created by bullet. Composite armors are used in military vehiclesto provide bulletproof protection.


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Classification Of Composite Materials

Composites

Particle-reinforcedcomposites

Fiber-reinforcedcomposites

Structuralcomposites


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Particle ReinforcedComposites

A. Particle Reinforced CompositesIn these composites the particles of various sizes and shapes or flakesare randomly dispersed within the matrix.

Non -metallicparticles in non -metallic matrix

Metallic particlesin nonmetallic

matrix

Metallic particlesin metallic matrix

Non -Metallicparticles in

metallic matrix


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1)Nonmetallic particles in nonmetallic matrix:E.g. Most common example is reinforced concrete where sand and rockare bonded by mix of cement and water that chemically react and harden.

2) Metallic particles in nonmetallic matrix:E.g. metal flakes suspended in paint. Silver flakes suspended in paint canbe applied to give good electrical conductivity.


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3)Metallic particles in Metallic matrix :E.g. Lead particles in copper alloys and steels to increase machinability;lead (natural lubricant) are used in bearing made of copper alloys.

4)Non-metallic particles in Metallic matrix: Ceramics suspended in metal matrix form cermets. E.g. Uranium oxideparticles in stainless steel is used as fuel element and Boron carbide in

stainless steel as control rods.


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B. Fiber-ReinforcedThe arrangement or orientation of the fibers relative to one another,

the fiber concentration, and the distribution all have a significantinfluence on the strength.

In situations when stress is applied in many directions, discontinuousfibers which are randomly oriented in the matrix material are used.

E.g. Carbon Fiber


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Continuous fiber composites.

It contains long continuous fibers as

the reinforcing phase which is moreefficient from point of view ofstrength.

It contains short fibers. These fiberscould be in one direction due to

which composite materials hasanisotropic property. Or they could berandomly distributed.

Discontinuous fiber composites.

1 2

3 4


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C. Structural CompositesIt consists of layers of at least 2 different materials that are bondedtogether. It combines the best properties of individual materials layers inorder to achieve more useful material.

Some types of these are;1) Bimetals.2) Clad metals.3) Laminated glass.4) Laminated fiber reinforced composites.


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1) Bimetals : They are laminates of two different metals with different

coefficients of thermal expansion. Under change in temperature,bimetals deflect by a certain amount and so are useful in temperaturemeasuring devices.

2) Clad metals : Cladding of one metal with other is done to obtain thebest properties of both. E.g.: 1 High strength aluminum alloys do not resistcorrosion and pure Al and some Al alloys are very corrosion resistant. Buthigh strength Al alloys covered with corrosion resistant Al alloy is a

composite material which has advantage of both.


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3) Laminated glass: Window glass is brittle and is dangerous as it can

break into many pieces. The plastic which is very tough, but is flexible andis susceptible to scratching. So, safety glasses are made of plastic calledpolyvinylbutryal sandwiched between two layers of glass. The glassprotects the plastic from scratching and gives it stiffness.

4) Laminated fiber reinforced composites: In this layers of fiber reinforcedmaterial are laminated with the fiber directions of each layer oriented indifferent directions to give different strength and stiffness in various

directions.E.g: Aircraft wing panels, tennis rackets.


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Manufacturing Of Composites

Following are most widely used methods of manufacturing composites inindustry:

Vacuum assisted resin transfer molding. (VARTM)

Filament Winding.

Hand layup.


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Vacuum AssistedResin Transfer Molding. (VARTM)

In RTM Process, first the pre-form is placed into the mold cavity as shown& a vacuum cover is placed.

Injection Gate

Pre-FormPlaced InsideThe Mould

Cavity.Mould


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the mold is then closed and air is removed using vacuum pump. Then low viscosity resin is injected into the cavity under pressure. Once the liquidresin fills the mold cavity, it cures, during which the resin hardens and

forms a firm bond with pre-form.

Injection Gate

MouldMould GetsFilled & ThenGets Cured

Air RemovedBy Vacuum

Pump


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After curing, the component is taken out of the mould box.

It allows one to obtain even very complex neat-shape parts with goodsurface finish. One of the example is automobile body panels are producedby this method.

FinishedComponent.


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General Layout of the VARTM process


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Filament WindingProcess is used in the fabrication of tubular composite parts.

Fiberglass roving strands are impregnated with a liquid thermosettingresin and wrapped onto a rotating mandrel.E.g. Composite pipes.


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Hand Layup

It’s a lowest-cost and most common process. First mould is waxed andsprayed with gel coat & cured with heating process (120 C). Then resin

with finely chopped fiberglass pieces is poured into this mould.


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Conclusion

Hence we can conclude that,1) Composite materials find wide applications as they have high strengthto weight ratio.2) They can be easily optimized as per application.

3) Composite materials are rapidly replacing conventional materials whileproviding the same strength but reduced weight.


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seminar on composite materials

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