Carbon textiles

8/11/2019 Carbon textiles

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What are Carbon-Carbon Composites?

Amorphous carbonmatrix composite

Carbon matrixreinforced by graphiticcarbon fibers

First developed in1958, but notintensively researcheduntil the Space ShuttleProgram


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C/C composites are lightweight, highC/C composites are lightweight, high --strength composite materials capablestrength composite materials capableof withstanding temperatures overof withstanding temperatures over30003000 C.C.

What are C/C Composites?

C/C composites use the strengthC/C composites use the strengthand modulus of carbon fibers toand modulus of carbon fibers toreinforce a carbon matrix to resistreinforce a carbon matrix to resistthe rigors of extreme environments.the rigors of extreme environments.


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Carbon-Carbon Composites Carbon-Carbon Composites are the

woven mesh of Carbon-fibers. Carbon-Carbon Composites are used for

their high strength and modulus of rigidity. Carbon-Carbon Composites' structure can

be tailored to meet requirements. Carbon-Carbon Composites are light

weight material which can withstandtemperatures up to 3000C


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Properties of C/CComposites

Excellent Thermal Shock Resistance(Over 2000 oC) Low Coefficient of Thermal Expansion High Modulus of Elasticity ( 200 GPa ) High Thermal Conductivity ( 100 W/m*K ) Low Density ( 1830 Kg/m^3 ) High Strength Low Coefficient of Friction ( in Fiber direction ) Thermal Resistance in non-oxidizing atmosphere High Abrasion Resistance High Electrical Conductivity

Non-Brittle Failure


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Production of C/CProduction of C/C Three dimensional woven carbon fiber structure

Pressure impregnation with liquid

Heat treated at 2550C

Impregnation, DENSIFICATION andgraphitization cycle repeated


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Representative WeaveConstructions


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Fabrication of C/C Composites

Liquid Phase Infiltration

Chemical Vapor Deposition


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PAN-based carbon fibers (the most popular type ofcarbon fibers).

In this method carbon fibers are produced byconversion of polyacrylonitrile (PAN) precursorthrough the following stages:Stretching filaments from polyacrylonitrileprecursor and their thermal oxidation at 200C.

The filaments are held intension.Carbonization in Nitrogen atmosphereat a temperature about 1200C for several

hours. During this stage non-carbonelements (O,N,H)volatilize resulting in enrichment of the fiberswith carbon.Graphitization at about 2500C.


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Carbon-Carbon Composites porous carbon-carbon composites

(carbon bonded carbon fiber (CBCF))Porosity content 70~90% high temperature

insulation


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Liquid Phase Infiltration Preparation of C/C fiber pre-form of desired shape and

structure Liquid pre-cursor : Petroleum pitch/ Phenolic resin/ Coal

tar Pyrolysis (Chemical deposition by heat in absence of O2 It is processed at 540 1000C under high pressure Pyrolysis cycle is repeated 3 to 10 times for desired

density

Heat Treatment converts amorphous C into crystalline C Temperature range of treatment :1500-3000C Heat treatment increases Modulus of Elasticity and

Strength


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Manufacturing Process :


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Processing of CBCF

Discontinuous fibers(mm in length)

Ground recycled CBCF(rework)

binder(phenolic resin)

water

mixer slurry moulding

water

drying Carbonization(950 )

High temp heattreatment

Product99.9%

50% carbon yieldfrom phenolic

vacuum

(fiber alignment) gaseousimpurities

low pressure

porous &anisotropic


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Chemical VaporDeposition

Preparation of C/C fiber pre-form of desired shapeand structure

Densification of the composite by CVD technique

Infiltration from pressurized hydrocarbon gases(Methane /Propane)at 990-1210C Gas is pyrolyzed from deposition on fibre surface Process duration depends on thickness of pre-form Heat treatment increases Modulus of Elasticity and

Strength This process gives higher strength and modulus of

elasticity


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Dense carbon-carbon composites

Discontinuous fibersContinuous fibers

Impregnation with thermosetting resins

(phenolic, furan

polyimide) pitch(polynucleararomatichydrocarbons)

pyrolysis Carbonization2500

Chemical vapour

deposition

DenseThick

enough?

product


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Limitation of CVD Hydrocarbon Gases Infiltrating into

interfilament surfaces and cracks ,sometimes these gases deposite on outercracks and leave lot of pores

Reinfiltration and densification required Month long process(for specific

applications)


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Stress-strain curveprocess dependent: Fig 4.30Form of fiber reinforcement: Fig 4.31


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Fatigue property


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Properties of Carbon-Carbon

http://www.hitco.com/products/corrosion/chemical/index.html


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Uses of Carbon-Carbon Composites Aircraft, F-1 racing

cars and train brakes

Space shuttle nose tipand leading edges

Rocket nozzles andtips

http://www.futureshuttle.com/conference/ThermalProtectionSystem/Curry_73099.pdf

http://www.fibermaterialsinc.com/frSW.htm

http://www.fibermaterialsinc.com/frSW.htm


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Optical Microscopy

Sample 3:


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Application High Performance Braking System Refractory Material Hot-Pressed Dies(brake pads) Turbo-Jet Engine Components Heating Elements Missile Nose-Tips Rocket Motor Throats Leading Edges(Space Shuttle, Agni missile) Heat Shields X-Ray Targets


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Applications Applications

NASA thermal protection systems

Nozzle throat inserts

Nosetips & leading edges

Space motor nozzles


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Products

Variety of high

temperatureapplications.


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Heat Shields

Baffle Heat Shield

Flexi Heat Shield


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Disadvantage :

Low oxidation resistance

Reacts with Oxygen at temperature above490C

i h d


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Protection Method:

Ceramic coatings(Carbides/Nitrides/oxides of Si,Zr,Ta,Al etc.)

Physical vapor deposition Plasma spraying Injecting with inorganic salts , borate &

silicate glass. Replacement of C/C matrix material by

Si-C.(inhibitors of B, Si, Zr compounds)

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