Welcome to Vince Kelly's Carbon Fiber Homepage
You can golf, ride, sail, tennis, drive, cycle, fish, decorate or even
FLY
CARBON FIBER !
picture courtesy of Boeing, www.boeing.com
The 787 is a family of airplanes in the 200- to 300-seat class that will carry passengers on routes between 3,500 and 8,500 nautical miles (6,500 to 16,000 kilometers). The 787 will allow airlines to offer passengers more of what they want: affordable, comfortable, nonstop, point-to-point travel to more destinations around the world. In addition to bringing big-jet ranges to mid-size airplanes, the 787 will fly at Mach 0.85, as fast as today's fastest commercial airplanes, while using much less fuel.
Using 20 percent less fuel per passenger than similarly sized airplanes, the 787 is designed for the environment with lower emissions and quieter takeoffs and landings. Inside the airplane, passengers will find cleaner air, bigger windows, more stowage space and improved lighting. Since the 787 program launch in April 2004, Boeing has sold more than 500 airplanes to customers from around the world, passing the 500-airplane order mark faster than any other airplane launch in the history of commercial aviation.
The 787 is the first commercial airplane to make the change from metal to composite structure. The majority of the 787's major structure is made out of composite material. The Dreamliner is the first commercial airplane to be built with a one-piece fuselage. Manufacturing a one-piece fuselage section eliminates 1,500 aluminum sheets and 40,000 to 50,000 fasteners.
Computer generated Images of the new Airbus
A350
pictures courtesy of Airbus
www.airbus.com
Airbus
A350
The development of this aircraft will
see a further significant use of carbon fiber composites.
My name is Vince Kelly , I hope to provide you with information
about carbon fiber, a unique material, used in a wealth of applications, all
over the world.
The Carbon Atom
Carbon fibers are derived from one of two precursor materials
-
PITCH
- PAN (Polyacrylonitrile fibers)
PITCH based carbon fibers have lower mechanical properties and are
therfore rarely used in critical structural applications.PAN based carbon
fibers are under continual development and are used in composites to make
materials of great strength and lightness
The raw material of PAN, acrylonitrile (AN), is a product of the chemical
industry and can be manufactured as follows:
Acrylonitrile (AN) is used as a raw material in acrylic fibers, ABS resin, AS
resin, synthetic rubber (NBR), acrylamide and other materials. Global production
capacity is 4.67 million tons, approximately 60% of which is consumed for
acrylic fibers. In the early manufacturing processes acetylene and hydrogen
cyanide (HCN) were used as a raw material, whereas today nearly all AN is
manufactured using what is called the Sohio process, whereby an ammoxidation
reaction are applied from inexpensive propylene and ammonia. Technological
advances, particularly surrounding research into improved catalysts for the
Sohio process, are proceeding, promoted by a concern for energy conservation and
lessening the environmental loading. The research aims include improved
productivity, reduced byproducts, and lesser wastewater and waste gas.
2. Sohio process
The Sohio process was perfected in 1960 by The
Standard Oil Co. of Ohio, owing to the development of an epoch-making catalyst
that synthesizes AN in a single-stage reaction using propylene and ammonia. The
reaction took place using the fluid-bed od. The P-Mo-Bi group is used as the
catalyst and favorable fluidized conditions are maintained by adjusting the
physical properties of the catalyst.
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The reaction gas contains not only AN, but also acetonitrile, hydrogen
cyanide and other byproduct gasses, so AN products are obtained by having the
reaction gas absorbed into water, then using evaporation separation.
5. Improved processes
The Sohio process was epoch-making at the
time it was developed, but improvements have been made in response to the
following conditions:
(1)The AN yield of approximately 60% was not very
high.
(2)The process circulated and used large amounts of water, requiring a
lot of energy.
(3)Approximately 1.5 tons to 2 tons of wastewater was
generated for every ton of AN produced.
(4) Treatment technology for the
waste gas was incomplete.
I. Improved catalyst
II. Steam reduction
Monsanto Corp. improved the water extractive
distillation stage of the Sohio process, reducing the amount of steam required
to produce one ton of AN by three tons.
III. Wastewater and waste gas treatment
AN wastewater normally
contains ammonium sulfate, along with small amounts of nitrile compounds,
hydrocyanic acid and compounds with a high boiling point. Alkali used to be
added to the wastewater before discharging, but nowadays wet oxidation processes
and biological treatment processes are being employed. Bayer Inc. has developed
the technology to recover high-grade ammonium sulfate from the gas generated as
a byproduct of the reaction.
Polymerisation of acrylonitrile produces PAN, the most common carbon fiber
feedstock
The basic unit of PAN is:
The Manufacturing Process
The conversion of PAN to carbon fibers is
normally made in 4 continuous stages
Oxidation
Carbonisation(Graphitisation)
Surface treatment
Sizing
OXIDATION involves heating the fibers to around 300 deg C in air. This
evolves hydrogen from the fibers and adds less volatile oxygen.
The polymer changes from a ladder to a stable ring structure, and the fiber
changes colour from white though brown to black.
 |
In this picture you see the fibre changing color.
The white PAN strands at the bottom pass through the air heated oven and
begin to darken
Quite quickly they turn to black and carbon fiber is like the Ford T, As
Henry said "Its any color you want, as long as it's black" |
Photo courtesy of Akzo Nobel
 |
In this picture you see the "skin-core effect.
The fatter fibers are not fully oxidized and have a core, which will make a
hollow low grade carbon fiber
This shows the importance of a high quality precursor of even cross
section |
Photo courtesy of Peter Morgan
The process here is very exothermic, fires are not uncommon
The resulting material is a textile fiber which is fireproof, some companies
actually sell this as an end product for example SGL Technic (Scotland),
under the tradename PANOX. (OXidised PAN)
CARBONISATION(GRAPHITISATION)
involves heating the fibers up to 3000 � C in an inert atmosphere, the fibers
are now nearly 100 % carbon.
The temperature will determine the grade of fiber produced:
Grades of Carbon Fiber
| Carbonisation Temperature (�C) |
to 1000 |
1000 - 1500 |
1500 - 2000 |
2000 + (Graphitisation)
| |
Grade of Carbon Fiber |
Low Modulus |
Standard Modulus |
Intermediate Modulus |
High Modulus |
| Modulus of Elasticity (GPa) |
to 200 |
200 - 250 |
250 - 325 |
325 + |
A summmary of typical properties of the various grades of
carbon fibers is given by Toray, although
the units of tensiometry are imperial (psi). (Conversion factor ~ 1.45). A good
guide to conversions can be found at SAMPE.
SURFACE TREATMENT forms chemical bonds to the carbon surface, to give
a better cohesion to the resin system of the composite
SIZING is a neutral finishing agent (usually epoxy) to protect the
fibers during further processing (eg prepregging) and to act as an interface to
the resin system of the composite
Where are carbon fibers used ?
Carbon fibers are used primarily in composites, these are structures
containing two or more components, in the case of fiber reinforced composites
this is the fiber and a resin. A composite containing two types of fiber,
eg. carbon and glass, is known as a hybrid composite structure. The
origins of textile reinforced composites are linked to the development of glass
fibers, which commenced in 1938 by the
Owens Corning Fiberglass Corporation (USA). Original large scale
applications included air filtration, thermal and electrical insulation and the
reinforcement of plastics. As the technology of textile reinforced composites
expanded, a growing demand from the aerospace industry for composite materials
with superior properties emeged. In particular, materials with (1) higher
specific strength, (2) higher specific moduli and (3) low density were required.
Other desirable properties are good fatigue resistance, and dimensional
stability. Carbon fibers were developed to meet this demand.
Carbon fibers are usually mixed with resin to form a
"Pre-Preg"
(Pre-impregnated)sheet, wound between release paper
A filming line used in the production of carbon fiber prepreg at SP
Systems
above photos
courtesy of SP Sytems
Comparison of Carbon Fiber and Steel
| Material |
Tensile Strength (GPa) |
Tensile Modulus (GPa) |
Density (g/ccm) |
Specific Strength (GPa)
| |
| Standard Grade Carbon Fiber |
3.5 |
230.0 |
1.75 |
2.00 |
| High Tensile Steel |
1.3 |
210.0 |
7.87 |
0.17 |
The superior properties of carbon fiber to steel and other metals
meant that the aerospace industry was an obvious market for composite materials,
the use of lighter materials in aircraft construction allows for fuel savings or
a greater payload, Carbon fibers are used extensively in both military and civil
aircraft structures. As the technology of producing composites advanced, other
fibers were developed to supply this market. For example Aramid and E-Glass, see
how they compare to carbon fibers:
Comparison of Fiber Reinforcements
| Material |
Tensile Strength (GPa) |
Tensile Modulus (GPa) |
Density (g/ccm) |
Specific Strength (GPa)
| |
| Carbon |
3.5 |
230.0 |
1.75 |
2.00 |
| Kevlar |
3.6 |
60.0 |
1.44 |
2.50 |
| E Glass |
3.4 |
22.0 |
2.60 |
1.31 |
Carbon fibers are also unique in the range of properties that can be found,
in this one generic type of material. As most carbon fiber manufactures are
working in a state of constant development and improvement, the range of fibers
now available to the structural engineer is always changing, look at the
developments of the last 15 years:
Carbon fibers are found in the intereiors of nearly all new aircraft
And
increasingly in more critical parts of the aircraft
The author of this page has been active in carbon fibers
since 1980. My name is Vince Kelly, I was born in Manchester England, my work in
carbon fibers has taken me to 1986 in Scotland, from 1986 to 2000 in Germany. I
am currently an international consultant in all aspects of carbon fiber
technology. I am also a professional member of the Society for the Advancement
of Material and Process Engineering SAMPE.
Founded in 1944, SAMPE is an international not-for-profit professional
Organization with approximately 5000 members worldwide. As the premier technical
Society in the fields of advanced materials and process engineering technology,
SAMPE is recognized for its strengths across numerous industries and markets.
The Society holds annual conferences and exhibitions in the USA, Europe and
Japan and publishes two widely recognized journals throughout the year.
Professional and Student Chapters actively hold local meetings, regional
workshops and seminars.
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