28-12-2010, 04:27 PM
Presented by:ARUSH TIWARI
COMPOSITES.pptx (Size: 806.83 KB / Downloads: 162)
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DEFINITION:
The use of two or more than two materials are called composites.
It is an advanced and latest technique.
In aircraft , it is used in only DORNIER-228.
It is a non metal alloy.
Reason behind the need:
Around 20-30 years ago, a survey was performed for the quality and cost of the aircraft in all over the world.
In that survey it was found that Indian aircrafts were poor in strength and cost were very high.
The reason behind this was, the Indians were very poor in man-hour rate and salary paid by company for their job were more.
The solution of this problem was that the mentality of Indians can never be changed, i.e. we can not compromise with Indians man-hour rate.
So a material was found which was more in strength and less in weight.
Its strength is more than metals.
Advantage:
High tensile and shear strength,
High impact strength,
High modulus of elasticity,
Less weight,
Strength is around 3 times than metals,
Low moisture absorption,
Easy repair,
No corrosion (very important property).
How it is made?
A sheet of fiber is moved from one place to another place.
In that way a series of jet machine are fixed.
This jet machine spray the resin (epoxy) over fiber.
So the resin is impregnated in the shells of fiber.
To avoid dust and moisture, a protective film is rolled over it at both side.
Then this is stored in cold storage having temperature -18˚C.
At this temperature the storage life of Prepreg is one year.
What is prepreg ?
It is a ready-made material to use on the moulding tool, supplied in sheet forms, impregnated with the epoxy resin in partial cured condition.
It is a composite material which is used in aircraft.
It is a very important material.
In all over world only “HEXCEL” composite company manufacture this Prepreg.
This company belongs to FRANCE.
In Dornier we use four type of Prepreg.