CC Composite Report

CARBON-CARBON COMPOSITE MATERIALSTextile Composite Materials

Report discusses about the Manufacturing & feature characteristics of Carbon-carbon composite materials. Applications & end use is discussed in the conclusion.

Adnan Ahmed Mazari11/1/2010

Contents

INTRODUCTION.................................................................................................................................................. 3

CARBON FIBRE.................................................................................................................................................... 3

CARBON FIBRE CLASSIFICATION.......................................................................................................................................3Based on carbon fiber properties:........................................................................................................................3Based on precursor fiber materials:.....................................................................................................................3Based on final heat treatmosphereent temperatureerature:..............................................................................3

CARBON FIBRE MANUFACTURING....................................................................................................................................4CARBON FIBRE (FROM PAN)..........................................................................................................................................4

Heat Treatmosphereent of PAN precursor fibers.................................................................................................5CARBON FIBRE (FROM RAYON).......................................................................................................................................5CARBON FIBRE (FROM PETROLEUMROLEUM PITCH)............................................................................................................6

Melt- spinning Mesophase Precursor Fibers........................................................................................................6Heat Treatmosphereent of Mesophase Precursor Fiber......................................................................................7

ADVANTAGES OF PETROLEUM PITCH FIBER OVER PAN BASED FIBER......................................................................................8

CARBON FIBRE GENERAL PROPERTIES................................................................................................................. 8

FABRICATION METHODS OF CC COMPOSITE:....................................................................................................... 8

LIQUID PHASE INFILTRATION:..........................................................................................................................................8Pitch Matrices......................................................................................................................................................8Thermoset Resin Matrices...................................................................................................................................8

GAS PHASE INFILTRATION PROCESS..................................................................................................................................9

CC COMPOSITE PROPERTIES................................................................................................................................ 9

CC COMPOSITE CHARACTERISTICS....................................................................................................................... 9

CC COMPOSITE APPLICATIONS.......................................................................................................................... 10

REFERENCES...................................................................................................................................................... 11

IntroductionA composite of carbon fiber in a graphite (carbon) matrix, also known as "Carbon Fiber Reinforced Carbon".Properties given for 50% fiber content. As with any fiber-reinforced composite, mechanical properties vary substantially with fiber content.Used for thermal shielding of space shuttle nose cone, in Formula One brake discs, and gas turbine engine parts.

Carbon-carbon (CC) materials are a generic class of composites similar to the graphite/epoxy family of polymer matrix composites. These materials can be made in a wide variety of forms from one-dimensional to n-dimensional using unidirectional tows, taps or woven cloth. Because of their multiformity their mechanical properties can be readily tailored.

Carbon materials have high strength & stiffness potential as well as high thermal and chemical stability in inert environments. These materials must however, be protected with coatings or surface sealants when used in an oxidizing environment.

Carbon FibreHigh strength, superior stiffness & light weight of carbon fibers have made them dominant reinforcement fibers used in high performance polymer matrix composites.

The properties of carbon fiber can vary over a wide range depending on the organic precursor & processing conditions used.

Carbon Fibre Classification

Based on carbon fiber properties: Ultra-high-modulus, type UHM (modulus >450Gpa) High-modulus, type HM (modulus between 350-450Gpa) Intermediate-modulus, type IM (modulus between 200-350Gpa) Low modulus and high-tensile, type HT (modulus < 100Gpa, tensile strength > 3.0Gpa)

Super high-tensile, type SHT (tensile strength > 4.5Gpa)

Based on precursor fiber materials: PAN-based carbon fibers Pitch-based carbon fibers Mesophase pitch-based carbon fibers Isotropic pitch-based carbon fibers Rayon-based carbon fibers Gas-phase-grown carbon fibers

Based on final heat treatmosphereent temperatureerature: Type-I, high-heat-treatmosphereent carbon fibers (HTT), where final heat treatmosphereent

temperatureerature should be above 2000°C and can be associated with high-modulus type fiber.

Type-II, intermediate-heat-treatmosphereent carbon fibers (IHT), where final heat treatmosphereent temperatureerature should be around or above 1500°C and can be associated with high-strength type fiber.

Type-III, low-heat-treatmosphereent carbon fibers, where final heat treatmosphereent temperatureeratures not greater than 1000°C. These are low modulus and low strength materials.

Carbon Fibre ManufacturingCarbon fibers are produced from 3 precursor material:

1. Rayon2. Polyacrylonitrile (PAN)3. Petroleumroleum pitch

Carbon Fibre (from PAN)Approximately 90% of all commercial carbon fibers are produced from PAN precursor fiber.

Solution spinning of PAN Precursor fibersCopolymer of PAN & acrylonitrile is dissolved in dimethylacetamide with conc of 15~30 % polymer by weight. It is then extruded through coagulating bath.

Solution-spun PAN fiber can be converted to carbon fibers with excellent mechanical properties. However, large amount of solvent are required for solution spinning which must be completely removed. This process adds cost and trace impurities ultimately can limit the properties of the final carbon fiber.

Melt-Assisted spinning of PAN precursor fibersAcrylonitrile copolymer is polymerized in an aqueous suspension which is then purifies & dewatered before extrusion. PAN copolymer is pelletized & extruded. Then polymer is plasticized by excess water, allowing it to form a homogenous melt.

Heat Treatmosphereent of PAN precursor fibers

Oxidation of PAN precursor fibersAccomplished by heating the PAN in air under tension at 220°C to 270°C for period that varies from 30 min to as much as 7hr.

Carbonizing & GraphitizingFinally fiber is carbonized in an inert atmosphereosphere to temperature ranging from 1000°C to 2800°C. Carbon content in the fiber depends upon carbonizing temperature.

Carbon Fibre (from Rayon)Cellulose fiber does not need oxidation for fusing but it improves carbon yield. Oxidation is done by heating in air at temperature of 400°C. After being stabilized fibers are carbonized & graphitized in an inert atmosphere & temperature similar to those used for PAN.

Over all yield for converting cell precursor fiber to carbon fiber ranges from 10~30% compared to 40~50% for the PAN which is direct result of the low carbon content.

Carbon Fibre (from Petroleumroleum Pitch)

Melt- spinning Mesophase Precursor Fibers Normally, extruder screw consists of 3 zones:

Solid feed Melting Pumping

Heat Treatmosphereent of Mesophase Precursor Fiber

Oxidation of Mesophase Precursor Fiber Typically, the as-spun mesophase fiber are heated to temperature of 300°C for 30min to 2hr. Apparatus for oxidizing the as-spun fiber without removing it from the spool used for spinning is shown in figure.

Carbonization & GraphitizationStabilized mesophase fibers are precarbonized for a few min at 900°C to 1000°C so that principle gases are evolved. Precarbonized fiber is then either carbonized or graphitized above 1000°C.

Surface treatmosphereent process is similar to that for PAN based fibers.

Advantages of Petroleum Pitch Fiber over PAN based fiber Starting material costs 40~50% less than PAN monomers. Pitch structure is closer to graphite than PAN, less energy is required to convert it to graphite,

and due to that shorter carbonization times are required in the production. Pitch fiber contains smaller % of Nitrogen, Hydrogen than PAN, so less material is driven off

during carbonization which gives 75% yield compared with only 40~45% for PAN.

Carbon Fibre General Properties

Comparison of Fiber Reinforcement

Comparison of Carbon fiber & Steel

Fabrication methods of CC composite:

Liquid Phase Infiltration: Pitch Matrices Thermoset resin Matrices

Pitch MatricesInfiltration can be performed at atmosphere pressure by heating to 1000°C under partial pressure of N2

gas. High pressure impregnation of 3-D fiber preforms with coal tar pitch increases the yield and density of the final CC composite.

Thermoset Resin MatricesPhenolics & Epoxy resins are 2 types of commonly used thermosetting resins. The material technology involves the impregnation of one layer of carbon fibers with a resin. This prepreg is partially cured to a fixed degree of tackiness & can be used immediately of refrigerated for 6~12 months.

Layers are combined & pyrolyzed at 150~300°C under 100~500 psi for 10 hr & subsequently densified by repeated carbonization cycles. Temperature of carbonization is increased slowly till 800°C.

Gas phase Infiltration Process Isothermal Chemical Vapor Deposition Thermal-Gradient Chemical Vapor Deposition Differential Pressure Chemical Vapor Deposition

The process begins with a preform in the desired shape of the part, usually formed from several layers of woven carbon fabric. The preform is heated in a furnace pressurized with an organic gas, such as methane, acetylene or benzene. Under high heat and pressure.

The gas decomposes and deposits a layer of carbon onto the carbon fibers. The gas must diffuse through the entire preform to make a uniform matrix, so the process is very slow, often requiring several weeks and several processing steps to make a single part.

CC composite Properties

CC composite Characteristics

CC composite Applications Aircraft interiors

Windmill blades

Brake linings

Tooling

Racing helmets

Solid rocket nozzles

Race car seats

Sports equipments

Automotive parts

References Carbon-carbon Materials and Composites - J. Buckley (ed) (1993)

Composite Manufacturing – S. K. Mazumdar (2001)

Design & Manufature of textile composites – Edited by A. C. Long (2005)

Ismail, N. "Strengthening of bridges using CFRP composites." Beijing, 217-224.