13-06-2012, 04:08 PM
Carbon fiber
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History of carbon fiber
This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (November 2009)
In 1958, Roger Bacon created high-performance carbon fibers at the Union Carbide Parma Technical Center, now GrafTech International Holdings, Inc., located outside of Cleveland, Ohio.[1] Those fibers were manufactured by heating strands of rayon until they carbonized. This process proved to be inefficient, as the resulting fibers contained only about 20% carbon and had low strength and stiffness properties. In the early 1960s, a process was developed by Dr. Akio Shindo at Agency of Industrial Science and Technology of Japan, using polyacrylonitrile(PAN) as a raw material. This had produced a carbon fiber that contained about 55% carbon.
The high potential strength of carbon fiber was realized in 1963 in a process developed at the Royal Aircraft Establishment at Farnborough, Hampshire. The process was patented by the UK Ministry of Defence then licensed by the National Research Development Corporation (NRDC) to three British companies: Rolls-Royce, already making carbon fiber, Morganite and Courtaulds. They were able to establish industrial carbon fiber production facilities within a few years, and Rolls-Royce took advantage of the new material's properties to break into the American market with its RB-211 aero-engine.
Public concern arose over the ability of British industry to make the best of this breakthrough. In 1969 a House of Commons select committee inquiry into carbon fiber prophetically asked: "How then is the nation to reap the maximum benefit without it becoming yet another British invention to be exploited more successfully overseas?" Ultimately, this concern was justified. One by one the licensees pulled out of carbon-fiber manufacture. Rolls-Royce's interest was in state-of-the-art aero-engine applications. Its own production process was to enable it to be leader in the use of carbon-fiber reinforced plastics. In-house production would typically cease once reliable commercial sources became available.
Unfortunately, Rolls-Royce pushed the state-of-the-art too far, too quickly, in using carbon fiber in the engine's compressor blades, which proved vulnerable to damage from bird impact. What seemed a great British technological triumph in 1968 quickly became a disaster as Rolls-Royce's ambitious schedule for the RB-211 was endangered. Indeed, Rolls-Royce's problems became so great that the company was eventually nationalized by the British government in 1971 and the carbon-fiber production plant was sold off to form "Bristol Composites".
Given the limited market for a very expensive product of variable quality, Morganite also decided that carbon-fiber production was peripheral to its core business, leaving Courtaulds as the only big UK manufacturer.
The company continued making carbon fiber, developing two main markets: aerospace and sports equipment. The speed of production and the quality of the product were improved.
Continuing collaboration with the staff at Farnborough proved helpful in the quest for higher quality, but, ironically, Courtaulds's big advantage as manufacturer of the "Courtelle" precursor now became a weakness. Low cost and ready availability were potential advantages, but the water-based inorganic process used to produce Courtelle made it susceptible to impurities that did not affect the organic process used by other carbon-fiber manufacturers.
Nevertheless, during the 1980s Courtaulds continued to be a major supplier of carbon fiber for the sports-goods market, with Mitsubishi its main customer. But a move to expand, including building a production plant in California, turned out badly. The investment did not generate the anticipated returns, leading to a decision to pull out of the area. Courtaulds ceased carbon-fiber production in 1991, though ironically the one surviving UK carbon-fiber manufacturer continued to thrive making fiber based on Courtaulds's precursor. Inverness-based RK Carbon Fibres Ltd has concentrated on producing carbon fiber for industrial applications, and thus does not need to compete at the quality levels reached by overseas manufacturers.
During the 1970s, experimental work to find alternative raw materials led to the introduction of carbon fibers made from a petroleum pitch derived from oil processing. These fibers contained about 85% carbon and had excellent flexural strength.
Structure and properties
A 6 μm diameter carbon filament (running from bottom left to top right) compared to a human hair.
Each carbon filament thread is a bundle of many thousand carbon filaments. A single such filament is a thin tube with a diameter of 5–8 micrometers and consists almost exclusively of carbon. The earliest generation of carbon fibers (e.g. T300, and AS4) had diameters of 7-8 micrometers.[2] Later fibers (e.g. IM6) have diameters that are approximately 5 micrometers.[2]
The atomic structure of carbon fiber is similar to that of graphite, consisting of sheets of carbon atoms(graphene sheets) arranged in a regular hexagonal pattern. The difference lies in the way these sheets interlock. Graphite is a crystalline material in which the sheets are stacked parallel to one another in regular fashion. The intermolecular forces between the sheets are relatively weak Van der Waals forces, giving graphite its soft and brittle characteristics. Depending upon the precursor to make the fiber, carbon fiber may be turbostratic or graphitic, or have a hybrid structure with both graphitic and turbostratic parts present. In turbostratic carbon fiber the sheets of carbon atoms are haphazardly folded, or crumpled, together. Carbon fibers derived from Polyacrylonitrile (PAN) are turbostratic, whereas carbon fibers derived from mesophase pitch are graphitic after heat treatment at temperatures exceeding 2200 C. Turbostratic carbon fibers tend to have high tensile strength, whereas heat-treated mesophase-pitch-derived carbon fibers have high Young's modulus (i.e., low elasticity) and high thermal conductivity.
Applications
Tail of an RC helicopter, made ofCarbon fiber reinforced polymer
Carbon fiber is most notably used to reinforce composite materials, particularly the class of materials known as carbon fiber or graphite reinforced polymers. Non-polymer materials can also be used as the matrix for carbon fibers. Due to the formation of metal carbides and corrosion considerations, carbon has seen limited success in metal matrix composite applications. Reinforced carbon-carbon (RCC) consists of carbon fiber-reinforced graphite, and is used structurally in high-temperature applications. The fiber also finds use in filtration of high-temperature gases, as anelectrode with high surface area and impeccable corrosion resistance, and as an anti-static component. Molding a thin layer of carbon fibers significantly improves fire resistance of polymers or thermoset composites because a dense, compact layer of carbon fibers efficiently reflects heat.[3]
The global demand on carbon fiber composites was valued at roughly US$10.8 billion in 2009, which declined 8-10% from the previous year. It is expected to reach US$13.2 billion by 2012 and to increase to US$18.6 billion by 2015 with an annual growth rate of 7% or more. Strongest demands come from aircraft & aerospace, wind energy as well as automotive industry.[4]
Synthesis
Each carbon filament is produced from a precursor polymer. The precursor polymer is commonly rayon,polyacrylonitrile (PAN) or petroleum pitch. For synthetic polymers such as rayon or PAN, the precursor is first spuninto filaments, using chemical and mechanical processes to initially align the polymer atoms in a way to enhance the final physical properties of the completed carbon fiber. Precursor compositions and mechanical processes used during spinning may vary among manufacturers. After drawing or spinning, the polymer fibers are then heated to drive off non-carbon atoms (carbonization), producing the final carbon fiber. The carbon fibers may be further treated to improve handling qualities, then wound on to bobbins. Wound bobbins are then used to supply machines that produce carbon fiber threads or yarn.[5]
[attachment=24372]
History of carbon fiber
This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (November 2009)
In 1958, Roger Bacon created high-performance carbon fibers at the Union Carbide Parma Technical Center, now GrafTech International Holdings, Inc., located outside of Cleveland, Ohio.[1] Those fibers were manufactured by heating strands of rayon until they carbonized. This process proved to be inefficient, as the resulting fibers contained only about 20% carbon and had low strength and stiffness properties. In the early 1960s, a process was developed by Dr. Akio Shindo at Agency of Industrial Science and Technology of Japan, using polyacrylonitrile(PAN) as a raw material. This had produced a carbon fiber that contained about 55% carbon.
The high potential strength of carbon fiber was realized in 1963 in a process developed at the Royal Aircraft Establishment at Farnborough, Hampshire. The process was patented by the UK Ministry of Defence then licensed by the National Research Development Corporation (NRDC) to three British companies: Rolls-Royce, already making carbon fiber, Morganite and Courtaulds. They were able to establish industrial carbon fiber production facilities within a few years, and Rolls-Royce took advantage of the new material's properties to break into the American market with its RB-211 aero-engine.
Public concern arose over the ability of British industry to make the best of this breakthrough. In 1969 a House of Commons select committee inquiry into carbon fiber prophetically asked: "How then is the nation to reap the maximum benefit without it becoming yet another British invention to be exploited more successfully overseas?" Ultimately, this concern was justified. One by one the licensees pulled out of carbon-fiber manufacture. Rolls-Royce's interest was in state-of-the-art aero-engine applications. Its own production process was to enable it to be leader in the use of carbon-fiber reinforced plastics. In-house production would typically cease once reliable commercial sources became available.
Unfortunately, Rolls-Royce pushed the state-of-the-art too far, too quickly, in using carbon fiber in the engine's compressor blades, which proved vulnerable to damage from bird impact. What seemed a great British technological triumph in 1968 quickly became a disaster as Rolls-Royce's ambitious schedule for the RB-211 was endangered. Indeed, Rolls-Royce's problems became so great that the company was eventually nationalized by the British government in 1971 and the carbon-fiber production plant was sold off to form "Bristol Composites".
Given the limited market for a very expensive product of variable quality, Morganite also decided that carbon-fiber production was peripheral to its core business, leaving Courtaulds as the only big UK manufacturer.
The company continued making carbon fiber, developing two main markets: aerospace and sports equipment. The speed of production and the quality of the product were improved.
Continuing collaboration with the staff at Farnborough proved helpful in the quest for higher quality, but, ironically, Courtaulds's big advantage as manufacturer of the "Courtelle" precursor now became a weakness. Low cost and ready availability were potential advantages, but the water-based inorganic process used to produce Courtelle made it susceptible to impurities that did not affect the organic process used by other carbon-fiber manufacturers.
Nevertheless, during the 1980s Courtaulds continued to be a major supplier of carbon fiber for the sports-goods market, with Mitsubishi its main customer. But a move to expand, including building a production plant in California, turned out badly. The investment did not generate the anticipated returns, leading to a decision to pull out of the area. Courtaulds ceased carbon-fiber production in 1991, though ironically the one surviving UK carbon-fiber manufacturer continued to thrive making fiber based on Courtaulds's precursor. Inverness-based RK Carbon Fibres Ltd has concentrated on producing carbon fiber for industrial applications, and thus does not need to compete at the quality levels reached by overseas manufacturers.
During the 1970s, experimental work to find alternative raw materials led to the introduction of carbon fibers made from a petroleum pitch derived from oil processing. These fibers contained about 85% carbon and had excellent flexural strength.
Structure and properties
A 6 μm diameter carbon filament (running from bottom left to top right) compared to a human hair.
Each carbon filament thread is a bundle of many thousand carbon filaments. A single such filament is a thin tube with a diameter of 5–8 micrometers and consists almost exclusively of carbon. The earliest generation of carbon fibers (e.g. T300, and AS4) had diameters of 7-8 micrometers.[2] Later fibers (e.g. IM6) have diameters that are approximately 5 micrometers.[2]
The atomic structure of carbon fiber is similar to that of graphite, consisting of sheets of carbon atoms(graphene sheets) arranged in a regular hexagonal pattern. The difference lies in the way these sheets interlock. Graphite is a crystalline material in which the sheets are stacked parallel to one another in regular fashion. The intermolecular forces between the sheets are relatively weak Van der Waals forces, giving graphite its soft and brittle characteristics. Depending upon the precursor to make the fiber, carbon fiber may be turbostratic or graphitic, or have a hybrid structure with both graphitic and turbostratic parts present. In turbostratic carbon fiber the sheets of carbon atoms are haphazardly folded, or crumpled, together. Carbon fibers derived from Polyacrylonitrile (PAN) are turbostratic, whereas carbon fibers derived from mesophase pitch are graphitic after heat treatment at temperatures exceeding 2200 C. Turbostratic carbon fibers tend to have high tensile strength, whereas heat-treated mesophase-pitch-derived carbon fibers have high Young's modulus (i.e., low elasticity) and high thermal conductivity.
Applications
Tail of an RC helicopter, made ofCarbon fiber reinforced polymer
Carbon fiber is most notably used to reinforce composite materials, particularly the class of materials known as carbon fiber or graphite reinforced polymers. Non-polymer materials can also be used as the matrix for carbon fibers. Due to the formation of metal carbides and corrosion considerations, carbon has seen limited success in metal matrix composite applications. Reinforced carbon-carbon (RCC) consists of carbon fiber-reinforced graphite, and is used structurally in high-temperature applications. The fiber also finds use in filtration of high-temperature gases, as anelectrode with high surface area and impeccable corrosion resistance, and as an anti-static component. Molding a thin layer of carbon fibers significantly improves fire resistance of polymers or thermoset composites because a dense, compact layer of carbon fibers efficiently reflects heat.[3]
The global demand on carbon fiber composites was valued at roughly US$10.8 billion in 2009, which declined 8-10% from the previous year. It is expected to reach US$13.2 billion by 2012 and to increase to US$18.6 billion by 2015 with an annual growth rate of 7% or more. Strongest demands come from aircraft & aerospace, wind energy as well as automotive industry.[4]
Synthesis
Each carbon filament is produced from a precursor polymer. The precursor polymer is commonly rayon,polyacrylonitrile (PAN) or petroleum pitch. For synthetic polymers such as rayon or PAN, the precursor is first spuninto filaments, using chemical and mechanical processes to initially align the polymer atoms in a way to enhance the final physical properties of the completed carbon fiber. Precursor compositions and mechanical processes used during spinning may vary among manufacturers. After drawing or spinning, the polymer fibers are then heated to drive off non-carbon atoms (carbonization), producing the final carbon fiber. The carbon fibers may be further treated to improve handling qualities, then wound on to bobbins. Wound bobbins are then used to supply machines that produce carbon fiber threads or yarn.[5]