Carbon Fiber

What is Carbon Fiber?

A carbon fiber is a long, thin strand of material about 0.0002-0.0004 in (0.005-0.010 mm) in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in microscopic crystals that are more or less aligned parallel to the long axis of the fiber. The crystal alignment makes the fiber incredibly strong for its size. Several thousand carbon fibers are twisted together to form a yarn, which may be used by itself or woven into a fabric. The yarn or fabric is combined with epoxy and wound or molded into shape to form various composite materials. Carbon fiber-reinforced composite materials are used to make aircraft and spacecraft parts, racing car bodies, golf club shafts, bicycle frames, fishing rods, automobile springs, sailboat masts, and many other components where light weight and high strength are needed.

Carbon fiber, alternatively graphite fiber, carbon graphite or CF, is a material consisting of fibers about 510 μm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in crystals that are more or less aligned parallel to the long axis of the fiber. The crystal alignment gives the fiber high strength-to-volume ratio (making it strong for its size). Several thousand carbon fibers are bundled together to form a tow, which may be used by itself or woven into a fabric.

Carbon fiber is a high-tensile fiber or whisker made by heating rayon or polyacrylonitrile fibers or petroleum residues to appropriate temperatures. Fibers may be 7 to 8 microns in diameter and are more that 90% carbonized.

These fibers are the stiffest and strongest reinforcing fibers for polymer composites, the most used after glass fibers. Made of pure carbon in form of graphite, they have low density and a negative coefficient of longitudinal thermal expansion.

Carbon fibers are very expensive and can give galvanic corrosion in contact with metals. They are generally used together with epoxy, where high strength and stiffness are required, i.e. race cars, automotive and space applications, sport equipment.

Depending on the orientation of the fiber, the carbon fiber composite can be stronger in a certain direction or equally strong in all directions. A small piece can withstand an impact of many tons and still deform minimally. The complex interwoven nature of the fiber makes it very difficult to break.

Characteristics/Properties of Carbon Fibers

1.      Physical strength, specific toughness, light weight.

2.      Good vibration damping, strength, and toughness.

3.      High dimensional stability, low coefficient of thermal expansion, and low abrasion.

4.      Electrical conductivity.

5.      Biological inertness and x-ray permeability.

6.      Fatigue resistance, self-lubrication, high damping.

7.      Electromagnetic properties.

8.      Chemical inertness, high corrosion resistance.

Classification of Carbon Fiber:

Based on modulus, strength, and final heat treatment temperature, carbon fibers can be classified into the following categories:

1.      Based on carbon fiber properties, carbon fibers can be grouped into:

• 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)

2.      Based on precursor fiber materials, carbon fibers are classified into:

• PAN-based carbon fibers
• Pitch-based carbon fibers
• Mesosphere pitch-based carbon fibers
• Isotropic pitch-based carbon fibers
• Rayon-based carbon fibers
• Gas-phase-grown carbon fibers

3.     Based on final heat treatment temperature, carbon fibers are classified into:

• High-heat-treatment carbon fibers (HTT), where final heat treatment temperature should be above 2000C and can be associated with high-modulus type fiber.
• Intermediate-heat-treatment carbon fibers (IHT), where final heat treatment temperature should be around or above 1500C and can be associated with high-strength type fiber.
• Low-heat-treatment carbon fibers, where final heat treatment temperatures not greater than 1000C. These are low modulus and low strength materials.

Application/Uses of Carbon Fiber

The two main applications of carbon fibers are in specialized technology, which includes aerospace and nuclear engineering, and in general engineering and transportation, which includes engineering components such as bearings, gears, cams, fan blades and automobile bodies. Recently, some new applications of carbon fibers have been found.

Such as rehabilitation of a bridge in building and construction industry, others include: decoration in automotive, marine, general aviation interiors, general entertainment and musical instruments and after-market transportation products. Conductivity in electronics technology provides additional new application.

Carbon fibers are classified by the tensile modulus of the fiber. The English unit of measurement is pounds of force per square inch of cross-sectional area, or psi. Carbon fibers classified as “low modulus” have a tensile modulus below 34.8 million psi (240 million kPa). Other classifications, in ascending order of tensile modulus, include “standard modulus,” “intermediate modulus,” “high modulus,” and “ultrahigh modulus.” Ultrahigh modulus carbon fibers have a tensile modulus of 72.5 -145.0 million psi (500 million-1.0 billion kPa). As a comparison, steel has a tensile modulus of about 29 million psi (200 million kPa). Thus, the strongest carbon fibers are ten times stronger than steel and eight times that of aluminum, not to mention much lighter than both materials, 5 and 1.5 times, respectively. Additionally, their fatigue properties are superior to all known metallic structures, and they are one of the most corrosion-resistant materials available, when coupled with the proper resins.
Thirty years ago, carbon fiber was a space-age material, too costly to be used in anything except aerospace. However today, carbon fiber is being used in wind turbines, automobiles, sporting goods, and many other applications. Thanks to carbon fiber manufacturers like ZOLTEK™ who are committed to the commercialization concept of expanding capacity, lowering costs, and growing new markets, carbon fiber has become a viable commercial product.

The raw material used to make carbon fiber is called the precursor. About 90% of the carbon fibers produced are made from polyacrylonitrile (PAN). The remaining 10% are made from rayon or petroleum pitch. All of these materials are organic polymers, characterized by long strings of molecules bound together by carbon atoms. The exact composition of each precursor varies from one company to another and is generally considered a trade secret.
During the manufacturing process, a variety of gases and liquids are used. Some of these materials are designed to react with the fiber to achieve a specific effect. Other materials are designed not to react or to prevent certain reactions with the fiber. As with the precursors, the exact compositions of many of these process materials are considered trade secrets.
The process for making carbon fibers is part chemical and part mechanical. The precursor is drawn into long strands or fibers and then heated to a very high temperature with-out allowing it to come in contact with oxygen. Without oxygen, the fiber cannot burn. Instead, the high temperature causes the atoms in the fiber to vibrate violently until most of the non-carbon atoms are expelled. This process is called carbonization and leaves a fiber composed of long, tightly inter-locked chains of carbon atoms with only a few non-carbon atoms remaining.

                    


Here is a typical sequence of operations used to form carbon fibers from polyacrylonitrile (PAN):

Spinning

• Acrylonitrile plastic powder is mixed with another plastic, like methyl acrylate or methyl methacrylate, and is reacted with a catalyst in a conventional suspension or solution polymerization process to form a polyacrylonitrile plastic.
• The plastic is then spun into fibers using one of several different methods. In some methods, the plastic is mixed with certain chemicals and pumped through tiny jets into a chemical bath or quench chamber where the plastic coagulates and solidifies into fibers. This is similar to the process used to form polyacrylic textile fibers. In other methods, the plastic mixture is heated and pumped through tiny jets into a chamber where the solvents evaporate leaving a solid fiber. The spinning step is important because the internal atomic structure of the fiber is formed during this process.
• The fibers are then washed and stretched to the desired fiber diameter. The stretching helps align the molecules within the fiber and provide the basis for the formation of the tightly bonded carbon crystals after carbonization.

Stabilizing

• Before the fibers are carbonized, they need to be chemically altered to convert their linear atomic bonding to a more thermally stable ladder bonding. This is accomplished by heating the fibers in air to about 390-590° F (200-300° C) for 30-120 minutes. This causes the fibers to pick up oxygen molecules from the air and rearrange their atomic bonding pattern. The stabilizing chemical reactions are complex and involve several steps, some of which occur simultaneously. They also generate their own heat, which must be controlled to avoid overheating the fibers. Commercially, the stabilization process uses a variety of equipment and techniques. In some processes, the fibers are drawn through a series of heated chambers. In others, the fibers pass over hot rollers and through beds of loose materials held in suspension by a flow of hot air. Some processes use heated air mixed with certain gases that chemically accelerate the stabilization.

Carbonizing

• Once the fibers are stabilized, they are heated to a temperature of about 1,830-5,500° F (1,000-3,000° C) for several minutes in a furnace filled with a gas mixture that does not contain oxygen. The lack of oxygen prevents the fibers from burning in the very high temperatures. The gas pressure inside the furnace is kept higher than the outside air pressure and the points where the fibers enter and exit the furnace are sealed to keep oxygen from entering. As the fibers are heated, they begin to lose their non-carbon atoms, plus a few carbon atoms, in the form of various gases including water vapor, ammonia, carbon monoxide, carbon dioxide, hydrogen, nitrogen, and others. As the non-carbon atoms are expelled, the remaining carbon atoms form tightly bonded carbon crystals that are aligned more or less parallel to the long axis of the fiber. In some processes, two furnaces operating at two different temperatures are used to better control the rate of heating during carbonization.

Treating the surface

• After carbonizing, the fibers have a surface that does not bond well with the epoxies and other materials used in composite materials. To give the fibers better bonding properties, their surface is slightly oxidized. The addition of oxygen atoms to the surface provides better chemical bonding properties and also etches and roughens the surface for better mechanical bonding properties. Oxidation can be achieved by immersing the fibers in various gases such as air, carbon dioxide, or ozone; or in various liquids such as sodium hypochlorite or nitric acid. The fibers can also be coated electrolytically by making the fibers the positive terminal in a bath filled with various electrically conductive materials. The surface treatment process must be carefully controlled to avoid forming tiny surface defects, such as pits, which could cause fiber failure.

Sizing

• After the surface treatment, the fibers are coated to protect them from damage during winding or weaving. This process is called sizing. Coating materials are chosen to be compatible with the adhesive used to form composite materials. Typical coating materials include epoxy, polyester, nylon, urethane, and others.
• The coated fibers are wound onto cylinders called bobbins. The bobbins are loaded into a spinning machine and the fibers are twisted into yarns of various sizes.

                    

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. Unfortunately, they had only limited compression strength and were not widely accepted.
What once began as a space age material for the aerospace market has now become commercialized.
Today, carbon fibers are an important part of many products, and new applications are being developed every year. The United States, Japan, and Western Europe are the leading producers of carbon fibers.

The future of Carbon Fiber is very bright, with vast potential in many different industries. Among them are:

• Alternate Energy –– Wind turbines, compressed natural gas storage and transportation, fuel cells
• Fuel Efficient Automobiles –– Currently used in small production, high performance automobiles, but moving toward large production series cars
• Construction and Infrastructure –– Light weight pre-cast concrete, earth quake protection
• Oil Exploration –– Deep Sea drilling platforms, buoyancy, umbilical, choke, and kill lines, drill pipes

                      

                                               

The Commercialization Concept

In order to fully develop carbon fibers in these industries and others, carbon fiber manufacturers need to continue to increase their capacity and change their mindset so that they are committed to the commercialization concept. The ideal conditions that would allow the carbon fiber industry to reach its vast potential are if carbon manufacturers:

• Target new applications
• Develop new and lower cost technology
• Reinvest profits with long term objectives in mind – no small operators focusing on low volume, high price
• Fully understand supplier’s costs and future strategy
• Identify and focus on market driver’s
• Work to aggressively reduce costs
• Consolidate so that weaker players help strengthen the stronger ones
• Share incremental improvements to help support market growth
• Understand that the primary competitors to carbon fibers are other materials, not other carbon fiber manufacturers

       

Mechanical Properties of Carbon Fibre Composite Materials, Fibre / Epoxy resin (120°C Cure)

Fibres @ 0° (UD), 0/90° (fabric) to loading axis, Dry, Room Temperature, Vf = 60% (UD), 50% (fabric)

	Symbol	Units	Std CF Fabric	HMCF Fabric	E glass Fabric	Kevlar Fabric	Std CF UD	HMCF UD	M55** UD	E glass UD	Kevlar UD	Boron UD	Steel S97	Al. L65	Tit. dtd 5173
Young’s Modulus 0°	E1	GPa	70	85	25	30	135	175	300	40	75	200	207	72	110
Young’s Modulus 90°	E2	GPa	70	85	25	30	10	8	12	8	6	15	207	72	110
In-plane Shear Modulus	G12	GPa	5	5	4	5	5	5	5	4	2	5	80	25
Major Poisson’s Ratio	v12		0.10	0.10	0.20	0.20	0.30	0.30	0.30	0.25	0.34	0.23
Ult. Tensile Strength 0°	Xt	MPa	600	350	440	480	1500	1000	1600	1000	1300	1400	990	460
Ult. Comp. Strength 0°	Xc	MPa	570	150	425	190	1200	850	1300	600	280	2800
Ult. Tensile Strength 90°	Yt	MPa	600	350	440	480	50	40	50	30	30	90
Ult. Comp. Strength 90°	Yc	MPa	570	150	425	190	250	200	250	110	140	280
Ult. In-plane Shear Stren.	S	MPa	90	35	40	50	70	60	75	40	60	140
Ult. Tensile Strain 0°	ext	%	0.85	0.40	1.75	1.60	1.05	0.55		2.50	1.70	0.70
Ult. Comp. Strain 0°	exc	%	0.80	0.15	1.70	0.60	0.85	0.45		1.50	0.35	1.40
Ult. Tensile Strain 90°	eyt	%	0.85	0.40	1.75	1.60	0.50	0.50		0.35	0.50	0.60
Ult. Comp. Strain 90°	eyc	%	0.80	0.15	1.70	0.60	2.50	2.50		1.35	2.30	1.85
Ult. In-plane shear strain	es	%	1.80	0.70	1.00	1.00	1.40	1.20		1.00	3.00	2.80
Thermal Exp. Co-ef. 0°	Alpha1	Strain/K	2.10	1.10	11.60	7.40	-0.30	-0.30	-0.30	6.00	4.00	18.00
Thermal Exp. Co-ef. 90°	Alpha2	Strain/K	2.10	1.10	11.60	7.40	28.00	25.00	28.00	35.00	40.00	40.00
Moisture Exp. Co-ef 0°	Beta1	Strain/K	0.03	0.03	0.07	0.07	0.01	0.01		0.01	0.04	0.01
Moisture Exp. Co-ef 90°	Beta2	Strain/K	0.03	0.03	0.07	0.07	0.30	0.30		0.30	0.30	0.30
Density		g/cc	1.60	1.60	1.90	1.40	1.60	1.60	1.65	1.90	1.40	2.00

** Calculated figures

Fibres @ +/-45 Deg. to loading axis, Dry, Room Temperature, Vf = 60% (UD), 50% (fabric)

	Symbol	Units	Std. CF	HM CF	E Glass	Std. CF fabric	E Glass fabric	Steel	Al
Longitudinal Modulus	E1	GPa	17	17	12.3	19.1	12.2	207	72
Transverse Modulus	E2	GPa	17	17	12.3	19.1	12.2	207	72
In Plane Shear Modulus	G12	GPa	33	47	11	30	8	80	25
Poisson’s Ratio	v12		.77	.83	.53	.74	.53
Tensile Strength	Xt	MPa	110	110	90	120	120	990	460
Compressive Strength	Xc	MPa	110	110	90	120	120	990	460
In Plane Shear Strength	S	MPa	260	210	100	310	150
Thermal Expansion Co-ef	Alpha1	Strain/K	2.15 E-6	0.9 E-6	12 E-6	4.9 E-6	10 E-6	11 E-6	23 E-6
Moisture Co-ef	Beta1	Strain/K	3.22 E-4	2.49 E-4	6.9 E-4

** Calculated figures

These tables are for reference / information only and are NOT a guarantee of performance
1 GPa = 1000 MPa = 1000 N/mm² = 145,000 PSI

These tables relate to only 2 of the many fibre orientations possible. Most components are made using combinations of the above materials and with the fibre orientations being dictated by the performance requirements of the product. Performance Composites Ltd. can assist with the design of components where appropriate.

Properties of Carbon Fiber:
Carbon fibers are characterised by high strength and great stiffness against bending and twisting forces. Steel fibers, which approach nearest to carbon in stiffness, are four times as dense as carbon, and carbon fibers have a very much superior stiffness to weight ratio. The properties of carbon fibers vary, depending on the conditions under which they are produced. The information which follows relates to a typical range of fibers.

• Fine Structure and Appearance.: Carbon fibres are black and smooth-surfaced, with a silky lustre. They are commonly of round cross-section, possibly with flattened sides.
• Ultimate Tensile Strength.: 1.80-2.40 kN/mm2 . (cf. steel 2 . 8 0 - 4.00).
• Breaking Extension.: 0.5%. ( c f steel 2.0%).
• Density.: 1.95 g / c m 3 . (cf. steel 7.80).
• Stiffness.: 3 5 0 - 4 1 0 kN/mm3 (cf. steel 2 0 7 ) .
• Stiffness/Weight Ratio.: 180-210 (cf. steel 27).
• Elastic Properties.: Load/extension curve almost linear to break. Hookean behaviour. Perfectly elastic to break.
• Specific Gravity.: 1.75-1.85.
• Effect of Moisture.: Nil.
• Flammability.: Not flammable.
• Effect of Age, Sunlight.: Nil.
• Effect of Chemicals, Solvents.: Inert. Hot air oxidation and strong oxidising agents (e.g. sodium hypochlorite) cause some erosion.
• Effects of Insects, Microorganisms.: Nil.

Carbon Fiber Properties categorised in general as below

1.        High Strength to weight ratio

2.       Rigidity

3.       Corrosion resistance

4.       Electrical Conductivity

5.        Fatigue Resistance

6.       Good tensile strength but Brittle

7.       Fire Resistance/Not flammable

8.        High Thermal Conductivity in some forms

9.       Low coefficient of thermal expansion

10.   Non poisonous

11.   Biologically inert

12.   X-Ray Permeable

13.   Relatively Expensive

14.   Requires specialized experience and equipment to use.

Carbon fibre is self-lubricating, it also has Excellent EMI (Electromagnetic Interference) Shielding Property

1- Carbon Fiber has High Strength to Weight Ratio (also known as specific strength)

Strength of a material is the force per unit area at failure, divided by its density. Any material that is strong AND light has a favourable Strength/Weight ratio. Materials such as Aluminium, titanium, magnesium, Carbon and glass fiber, high strength steel alloys all have good strength to weight ratios. It is not surprising that Balsa wood comes in with a high strength to weight ratio.

The following figures are offered for comparison only and will vary depending on composition, alloy, type of spider, density of wood etc. The units are kN.m/kg.

Spectra fiber                              3619

Kevlar                                          2514

Carbon Fibre                               2457

Glass Fibre                                   1307

Spider Silk                                     1069

Carbon Epoxy Composite             785

Balsa axial load                               521

Steel alloy                                        254

Aluminium alloy                               222

polypropylene                                 89

Oak                                                   87

Nylon                                               69

Note that strength and rigidity are different properties, strength is resistance to breaking, rigidity is resistance to bending or stretching.

Because of the way the crystals of carbon fibre orient in long flat ribbon or narrow sheets of honeycomb crystals, the strength is higher running lengthwise than across the fibre. That is why designers of carbon fibre objects specify the direction the fibre should be laid to maximize strength and rigidity in a specific direction. The fibre being aligned with the direction of greatest stress.

Pan based precursor carbon fibre has higher strength than pitch based carbon fibre which has higher stiffness.

2- Carbon Fiber is very Rigid

Rigidity or stiffness of a material is measured by its Young Modulus and measures how much a material deflects under stress. Carbon fiber reinforced plastic is over 4 times stiffer than Glass reinforced plastic, almost 20 times more than pine, 2.5 times greater than aluminium. For more information on stiffness and how it is measured, plus a comparison table of different materials see my Young Modulus page.

Remember stress is force, strain is deflection such as bending or stretching

3- Carbon fiber is Corrosion Resistant and Chemically Stable.

Although carbon fibers themselves do not deteriorate measurably, Epoxy is sensitive to sunlight and needs to be protected. Other matrices (whatever the carbon fiber is embedded in) might also be reactive.

Carbon fibres can be affected by strong oxydizing agents

Composites made from carbon fibre must either be made with UV resistant epoxy (uncommon), or covered with a UV resistant finish such as varnishes.

4- Carbon fiber is Electrically Conductive

This feature can either be useful or be a nuisance. In Boat building conductivity has to be taken into account just as Aluminium conductivity comes into play. Carbon fiber conductivity can facilitate Galvanic Corrosion in fittings. Careful installation can reduce this problem.

Carbon Fiber dust can accumulate in a shop and cause sparks or short circuits in electrical appliances and equipment.

5- Fatigue Resistance is good

Resistance to Fatigue in Carbon Fiber Composites is good. However when carbon fiber fails it usually fails catastrophically without significant exterior signs to announce its imminent failure.

Damage in tensile fatigue is seen as reduction in stiffness with larger numbers of stress cycles, (unless the temperature is high)

Test have shown that failure is unlikely to be a problem when cyclic stresses coincide with the fiber orientation. Carbon fiber is superior to E glass in fatigue and static strength as well as stiffness.

The orientation of the fibers AND the different fiber layer orientation, have a great deal of influence on how a composite will resist fatigue (as it has on stiffness). The type of forces applied also result in different types of failures. Tension, Compression or Shear forces all result in markedly different failure results.

Paper by Oak Ridge National Laboratory, on test of carbon fiber composites intended for automotive use. American Institute of Aeronautics and Astronautics, test for materials to be used in wind turbines blades.

6- Carbon Fiber has good Tensile Strength

Tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, or failing. Necking is when the sample cross-section starts to significantly contract. If you take a strip of plastic bag, it will stretch and at one point will start getting narrow. This is necking. Tensile Strength is measured in Force per Unit area. Brittle materials such as carbon fiber does not always fail at the same stress level because of internal flaws. They fail at small strains. (in other words there is not a lot of bending or stretching before catastrophic failure) Weibull modulus of brittle materials

Testing involves taking a sample with a fixed cross-section area, and then pulling it gradually increasing the force until the sample changes shape or breaks. Fibers, such as carbon fibers, being only 2/10,000th of an inch in diameter, are made into composites of appropriate shapes in order to test.

Units are MPa This table is offered as a comparison only since there are a great number of variables.

Carbon steel 1090                                              650

High density polyethylene (HDPE)                   37

Polypropylene                                               19.7-80

High density polyethylene                                 37

Stainless steel AISI 302                                   860

Aluminium alloy 2014-T6                                 483

Aluminium alloy 6063-T6                                 248

E-Glass alone                                                   3450

E-Glass in a laminate                                       1500

Carbon fiber alone                                          4127

Carbon fiber in a laminate                             1600

Kevlar                                                     2757

Pine wood (parallel to grain)                          40

NOTE: When testing carbon fiber, and other fibres and non homogenious materials, samples much be made that are consistant and comparable. This is not a simple procedure. If you read research where strength/stiffness is compared, the researchers will always explain how their samples were manufactured including the type of matrix, alignment of fibres, ratio of fibres to matric among other factors. This difficulty explains why measurements can vary quite a lot between research results.

7- Fire Resistance/Non Flammable

Here is an article on recycling carbon fibre by burning off the matrix.

Carbon fibre is classified as non conbustible and has no listed flash point. If it is exposed to high heat in the presence of fuel burning, it can eventually oxidize but as soon as the flame and fuel is removed the flame does not continue.

Because carbon fibre is almost always used in a matrix such as epoxy, plastic or concrete, the tolerance of the matrix to high temperature is the more significant factor.

Depending upon the manufacturing process and the precursor material, carbon fiber can be be made to feel quite soft to the hand and can be made into or more often integrated into protective clothing for firefighting. Nickel coated fiber is an example. Because carbon fiber is also chemically very inert, it can be used where there is fire combined with corrosive agents.HIGH TEMP FELT WELDING BLANKET - BLACK, 18" X 24" These felt carbon fibre blankets are also used to protect substrates when doing plumbing soldering.

8- Thermal Conductivity of Carbon Fiber

See my article on Heat Conductivity of Carbon Based materials including carbon fibre, nanotubes and graphene.

Thermal conductivity is the quantity of heat transmitted through a unit thickness, in a direction normal to a surface of unit area, because of a unit temperature gradient, under steady conditions. In other words it's a measure of how easily heat flows through a material.

There are a number of systems of measures depending on metric or imperial units.

1 W/(m.K) = 1 W/(m.oC) = 0.85984 kcal/(hr.m.oC) = 0.5779 Btu/(ft.hr.oF)

This table is only for comparison. The units are W/(m.K)

Air                                                 .024

Aluminium                                     250

Concrete                                     .4 - .7

Carbon Steel                                 54

Mineral Wool insulation            .04

Plywood                                         .13

Quartz                                             3

Pyrex Glass                                      1

Pine                                                  .12

Carbon Fiber Reinforced Epoxy 24

Because there are many variations on the theme of carbon fiber it is not possible to pinpoint exactly the thermal conductivity. Special types of Carbon Fiber have been specifically designed for high or low thermal conductivity. There are also efforts to Enhance this feature.

The Materials Information Society has a page on "graphite" AKA Carbon Fiber

9- Low Coefficient of Thermal Expansion

This is a measure of how much a material expands and contracts when the temperature goes up or down.

Units are in Inch / inch degree F, as in other tables, the units are not so important as the comparison.

Steel                                           7

Aluminium                               13

Kevlar                                     3 or lower

Carbon Fiber woven            2 or less

Carbon fiber unidirectional  -1 to +8

Fiberglass                                     7-8

Brass                                             11

Carbon fiber can have a broad range of CTE's, -1 to 8+, depending on the direction measured, the fabric weave, the precursor material, Pan based (high strength, higher CTE) or Pitch based (high modulus/stiffness, lower CTE).

In a high enough mast differences in Coefficients of thermal expansion of various materials can slightly modify the rig tensions.

Low Coefficient of Thermal expansion makes carbon fiber suitable for applications where small movements can be critical. Telescope and other optical machinery is one such application.

10-11-12 Non Poisonous, Biologically Inert, X-Ray Permeable

These quality make Carbon fiber useful in Medical applications. Prosthesis use, implants and tendon repair, x-ray accessories surgical instruments, are all in development.

Although not poisonous, the carbon fibers can be quite irritating and long term unprotected exposure needs to be limited. The matrix either epoxy or polyester, can however be toxic and proper care needs to be exercised.

13- Carbon Fiber is Relatively Expensive

Although it offers exceptional advantages of Strength, Rigidity and Weight reduction, cost is a deterrent. Unless the weight advantage is exceptionally important, such as in aeronautics applications or racing, it often is not worth the extra cost. The low maintenance requirement of carbon fiber is a further advantage.

It is difficult to quantify cool and fashionable. Carbon fiber has an aura and reputation which makes consumers willing to pay more for the cachet of having it.

You might need less of it compared to fiberglass and this might be a saving.

Fibre Glast Real Carbon Fiber Fabric - 3K, 2 X 2 - Twill Weave - 1 yd Roll

Noahs supplies Carbon Fiber and Glass cloth to amateur boat builders, wander in their online catalog and compare the prices. (Canadian Store)

14- Carbon Fibers are brittle

The layers in the fibers are formed by strong covalent bonds. The sheet-like aggregations readily allow the propagation of cracks. When the fibers bend they fails at very low strain. In other words carbon fibre does not bend much before failing.

15- Carbon Fiber is not yet geared to Amateur techniques.

In order to maximize Carbon Fiber Characteristics, a relatively high level of technical excellence must be achieved. Imperfections and air bubbles can significantly affect performance. Typically, autoclaves, or vacuum equipment is required. Moulds and mandrels are major expenses as well.

The success of any amateur carbon fiber construction will be closely linked to the skill and care taken.

Application Carbon Fiber is given as shortly:

• Aerospace, road and marine transport, sporting goods.
• Missiles, aircraft brakes, aerospace antenna and support structure, large telescopes, optical benches, waveguides for stable high-frequency (GHz) precision measurement frames.
• Audio equipment, loudspeakers for Hi-fi equipment, pickup arms, robot arms.
• Automobile hoods, novel tooling, casings and bases for electronic equipments, EMI and RF shielding, brushes.
• Medical applications in prostheses, surgery and x-ray equipment, implants, and tendon/ligament repair.
• Textile machinery, genera engineering.
• Chemical industry; nuclear field; valves, seals, and pump components in process plants.
• Large generator retaining rings, radiological equipment.

Carbon fibre is sometimes used in conjunction with fiberglass because of their similar manufacturing processes, an example of this would be the Corvette ZO6 where the front end is carbon fibre and the rear is fiberglass. Carbon fiber is however, far stronger and lighter than fiberglass.

Carbon fibre can be found in a wide range of performance vehicles including sports cars, superbikes, pedal bikes (where they are used to make frames), powerboats and it is often used in the tuning and customizing industry where attractive woven panels are left unpainted to 'show off' the material.