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Carbon Fiber Processing Production methods, properties and composite applications Corey Behrens February 19, 2007.

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Presentation on theme: "Carbon Fiber Processing Production methods, properties and composite applications Corey Behrens February 19, 2007."— Presentation transcript:

1 Carbon Fiber Processing Production methods, properties and composite applications Corey Behrens February 19, 2007

2 Properties of Carbon Fibers High strength High strength High stiffness High stiffness Withstand temperatures to >2500 o C Withstand temperatures to >2500 o C High strength/weight ratio High strength/weight ratio Tensile moduli range from 4x10 6 psi to 100x10 6 psi Tensile moduli range from 4x10 6 psi to 100x10 6 psi

3 Methods of producing Carbon Fiber All commercial C.F.’s from 3 processes: All commercial C.F.’s from 3 processes: Polyacrylonitrile (PAN) Polyacrylonitrile (PAN) Rayon (cellulose) Rayon (cellulose) Mesophase Petroleum Pitch Mesophase Petroleum Pitch New method for discontinuous C.F. New method for discontinuous C.F. Vapor Growth (high performance application) Vapor Growth (high performance application)

4 PAN process Accounts for 90% of commercial C.F.’s Accounts for 90% of commercial C.F.’s 93-95% acrylonitrile units 93-95% acrylonitrile units PAN decomposes below its melt temperature PAN decomposes below its melt temperature True Melt process not possible True Melt process not possible Therefore extruded into filament form Therefore extruded into filament form

5 Process Method Copolymer is first dissolved in suitable solvent Copolymer is first dissolved in suitable solvent e.g.Dimethylacetamide e.g.Dimethylacetamide 15-30% polymer by weight 15-30% polymer by weight extruded through a spinneret extruded through a spinneret large # of approx.100μm capillary holes large # of approx.100μm capillary holes enters coagulating bath (Wet spinning) enters coagulating bath (Wet spinning) Also hot gas environments Also hot gas environments 1-2 stages of further stretching 1-2 stages of further stretching Aligns polymer molecules parallel to fiber axis Aligns polymer molecules parallel to fiber axis Molecular orientation must be locked into place Molecular orientation must be locked into place Effects final mechanical properties of C.F.’s Effects final mechanical properties of C.F.’s

6 PAN precursor fiber process

7 Considerations of PAN Wet spinning Wet spinning Requires excessive solvent Requires excessive solvent Necessitates removal from fiber, solvent recovery Necessitates removal from fiber, solvent recovery $$$ $$$ Trace impurities limit final C.F. properties Trace impurities limit final C.F. properties BASF pseudo-melt alternative BASF pseudo-melt alternative Acrylonitrile copolymer polymerized in aq. Soln. Acrylonitrile copolymer polymerized in aq. Soln. Purified, dewatered, palletized Purified, dewatered, palletized Homogenous melt below degradation temp. Homogenous melt below degradation temp. Eliminates need for expensive solvent Eliminates need for expensive solvent Lower waste water requirements Lower waste water requirements

8 BASF PAN pseudo-melt

9 Production of Carbon Fiber from PAN Heating/Stretching Heating/Stretching Pre-carbonization Pre-carbonization Carbonization Carbonization Surface Treatment Surface Treatment

10 Chemistry of carbon fiber production

11 Heating/Stretching Stretching ( %) Stretching ( %) o C for 30min to 7hrs o C for 30min to 7hrs Temp./Time dependent on composition/diameter of Precursor Temp./Time dependent on composition/diameter of Precursor Chemical changes Chemical changes Cyclization of nitrile groups Cyclization of nitrile groups Dehydration of saturated C-C bonds Dehydration of saturated C-C bonds Oxidation Oxidation Generates CO 2 and HCN Generates CO 2 and HCN Large furnace + Drive rollers Large furnace + Drive rollers Controlled tension essential for alignment Controlled tension essential for alignment PAN carbon content: 54% PAN carbon content: 54%

12 Pre-carbonization Heating up to 1100 o C Heating up to 1100 o C Non-Carbon elements driven off Non-Carbon elements driven off Initially larger molecules Initially larger molecules CH 4 H 2 O NH 3 N 2 HCN CO 2 CO CH 4 H 2 O NH 3 N 2 HCN CO 2 CO Slower heating rate Slower heating rate

13 Carbonization 1100 o C – 2800 O C 1100 o C – 2800 O C Only small diatomic molecules Only small diatomic molecules H 2 N 2 H 2 N 2 Faster heating rate possible Faster heating rate possible Graphitization above ~1800 o C Graphitization above ~1800 o C Final C content: 80% to >99% Final C content: 80% to >99% Temp. dependent Temp. dependent Overall Yield: 40-45% Overall Yield: 40-45%

14 Surface Treatment Improves bonding with polymeric matrix materials Improves bonding with polymeric matrix materials Increases oxygenated groups at surface Increases oxygenated groups at surface Gassing at elevated temps. Gassing at elevated temps. Sodium hypochlorite solution Sodium hypochlorite solution Nitric Acid Nitric Acid

15 C.F.’s from PAN precursor Fibers

16 PAN and Pitch processing

17 Rayon (cellulose) precursor fibers Typically low modulus (4x10 6 psi) Typically low modulus (4x10 6 psi) Fiber heated to 400 o C, pyrolization of cellulose Fiber heated to 400 o C, pyrolization of cellulose Carbonization at >1000 o C Carbonization at >1000 o C Graphitized at >2000 o C Graphitized at >2000 o C High modulus obtained by stretching at final heat treatment stage High modulus obtained by stretching at final heat treatment stage

18 Mesophase Pitch Precursors Same general process as PAN Same general process as PAN Low tensile strength of precursor fibers Low tensile strength of precursor fibers Melt-spin is used Melt-spin is used Do not require stretching process to maintain preferred alignment Do not require stretching process to maintain preferred alignment

19 Final Carbon Fibers Woven, Braided, or Wound Woven, Braided, or Wound Unidirectional lay-ups Unidirectional lay-ups Multi-directional weaves Multi-directional weaves Strength limiting factors Strength limiting factors Purity of precursor Purity of precursor Precursor void content Precursor void content Temperature Temperature Tension Tension

20 C.F.’s from differing processes

21 Carbon vs. Steel Material Tensile Strength (GPa) Tensile Modulus (GPa) Density (g/ccm) Specific Strength (GPa) Standard Grade Carbon Fiber High Tensile Steel

22 Modulus Classifications Ultra high elastic modulus type (UHM) Ultra high elastic modulus type (UHM) High elastic modulus type (HM) High elastic modulus type (HM) Intermediate elastic modulus type (IM) Intermediate elastic modulus type (IM) Standard elastic modulus type (HT) Standard elastic modulus type (HT) Low elastic modulus type (LM) Low elastic modulus type (LM)

23 Carbon Fiber Modulus

24 Composite uses of carbon fibers Polymer-Matrix Composites Polymer-Matrix Composites Metal-Matrix Composites Metal-Matrix Composites Carbon-Matrix Composites Carbon-Matrix Composites Ceramic-Matrix Composites Ceramic-Matrix Composites Hybrid composites Hybrid composites

25 Carbon-Carbon Composites Carbon substrate in Carbonaceous Matrix Carbon substrate in Carbonaceous Matrix Same element does not simplify composite behavior Same element does not simplify composite behavior each constituent has a wide range of forms each constituent has a wide range of forms Carbon fibers continuous and woven Carbon fibers continuous and woven Disadvantages Disadvantages High fabrication cost High fabrication cost Poor oxidation resistance Poor oxidation resistance Poor inter-laminar properties Poor inter-laminar properties

26 Fabrication of C-C Composites Liquid phase impregnation (LPI) Liquid phase impregnation (LPI) Hot isostatic pressure impregnation carbonization (HIPIC) Hot isostatic pressure impregnation carbonization (HIPIC) Hot pressing Hot pressing Chemical Vapor Infiltration (CVI) Chemical Vapor Infiltration (CVI)

27 Applications of C-C Composites Aircraft Brakes Aircraft Brakes Heat Pipes Heat Pipes Reentry vehicles Reentry vehicles Rocket motor nozzles Rocket motor nozzles Hip replacements Hip replacements Biomedical implants Biomedical implants Tools and dies Tools and dies Engine pistons Engine pistons Electronic heat sinks Electronic heat sinks Automotive and motorcycle bodies Automotive and motorcycle bodies Bicycles Bicycles

28 Buckley, John D. and Dan. D. Edie, eds. Carbon- Carbon Materials and Composites Noyes Publications: Park Ridge, NJ 1993 Buckley, John D. and Dan. D. Edie, eds. Carbon- Carbon Materials and Composites Noyes Publications: Park Ridge, NJ 1993 Chung, Deborah. Carbon Fiber Composites. Butterworth-Heinemann, Boston 1994 Chung, Deborah. Carbon Fiber Composites. Butterworth-Heinemann, Boston 1994 Japan Carbon Fiber Manufacturer’s Association Japan Carbon Fiber Manufacturer’s Association Further Reading


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