Composites PDF UPES

8/7/2019 Composites PDF UPES

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Vikas Misra

AP (SG)

UPES,Dehradun


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CompositesComposite material is combination of two or more

chemically unlike materials with distinct boundariesbetween them.

Such materials have their own specificproperties & are usually different from theirindividual material properties.

The properties such as strength, resistance toheat or some other property of composites aremuch better than the properties of individual

materials from which they are made.


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Composites include the following :

Multiphase metal alloys

Ceramics

Polymers

Some common composites are Pearlitic steel,wood,RCC, automobile tyres

Composites materials can be divided into 3

main classes :-Fibre Reinforced materials

Laminated Materials

Disperse Materials


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Fibre Reinforced materials: Here fibres of

High strength materials are introduced intothe soft & ductile matrix.

The strength of soft & ductile matrix getsincreased by high strength fibres

the resulting composite material will havehigh stiffness, high Specific strength( UTS/density),elevated temp strength & high fracturetoughness.

Fibres mainly bear the load & the matrixtransfers & distributes the external load to

the fibres.


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.Also matrix protects the fibres from externalactions & imparts certain Physico chemicalproperties such as resistance to corrosion &oxidation, electrical & thermal conductivity etc.

The properties of composite materials atelevated temp may get affected by thereactions occurring between the matrix &fibres, this may result in dissolution or softening

of fibres & may also form brittle layer atinterfaces.

Fibres can be metals or nonmetals.


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The common metallic fibres used incomposite materials are of Boron, Be,Mo,T,SS,& non metallic fibres are of C,Glass, Silica,alumina, silicon carbide & Aramide.

Aramide is an aromatic polymaide fibre with a

very rigid molecular structure & is marked undertrade name KEVLAR.

Matrix can also be metallic or non metallic,

common metallic matrices are of Al,Cu,Titaniumalloys & nonmetallic matrices are of unsaturatedpolyesters & epoxy resins.


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Fibre reinforced composites have hugediversified applications. Like helmets, car &

jeep bodies, bikes, vehicle tyres, aircraft partssteel rods etc.

Laminated Materials : Here the composite

material consists of two or more layers ofunlike components. Like Laminated Plywood, Alclad aluminum alloy, copper clad Stainlesssteel .

Thermostatic controls consisting of a bimetallicstrip of copper & Ni used to control temperaturesin ovens & furnaces is also a composite material

of this type.


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The properties of these composites & fibrereinforced composites are highly sensitive to

direction of loading w.r.t. the direction oflamillae or fibres.

Disperse Materials : Here the particles of one

material are distributed as a mechanicalmixture into the other (Base).

This is the same as dispersion hardening of

strengthening. Common example of suchcomposites are Sintered Aluminum powder,thoriated tungsten, dispersed Nickel.


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Large number of methods are available forproduction of composite materials,

Important One are Unidirectionalsolidification, infiltration of molten metal,plasma spraying, electroplating, diffusion

bonding, P/M.

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Composites PDF UPES