A Complete Guide: What Is Carbon Fiber Material and What Is It Used For?

Carbon fiber is a fiber material that can greatly improve the performance of automobiles. It is generally used in various parts of the car body, such as bumpers, rearview mirrors, spoilers, and so on. It can not only increase the hardness of the car body, but also greatly reduce the weight of the car body, and reduce the maintenance cost of the car body. It can be said to be a material with huge returns for a small investment.

This article will give everyone a detailed breakdown of the material “carbon fiber”.

What is Carbon Fiber?

Carbon Fiber (CF for short) is a high-performance fiber material made from organic precursor fibers such as polyacrylonitrile (PAN) or pitch, through a carbonization process at high temperature in an inert environment. Its carbon content is usually above 90%, and can even reach as high as 99%. The diameter of a single carbon fiber filament is only about 5-10 microns, almost one tenth of a human hair.

A 6-micrometer-diameter carbon fiber (top) and a human hair (bottom) as seen under a microscope

Inside, the carbon atoms are highly parallel arranged in crystal form along the long axis of the fiber, forming a hexagonal ring-shaped graphitized structure. It is this stable structure that gives carbon fiber components extremely high strength. Carbon fiber, just as its name implies, not only has the functional characteristics of carbon materials, but also has the soft characteristics of textile fibers, making it extremely malleable.

The tensile strength of carbon fiber is 5-10 times that of ordinary steel, but its density is only about 1/4 of steel (about 1.5-2.0 g/cm³). Compared with steel of the same weight, the structural strength of carbon fiber is much higher.

Extremely high strength and extremely light weight—the combination of these two makes carbon fiber material almost perfect. In addition, carbon fiber also has the advantages of high elastic modulus, excellent corrosion resistance, high temperature tolerance (above 2000°C in non-oxidizing environments), and extremely low thermal expansion coefficient. It is not easy to deform even when temperature changes rapidly from high to low, which is the icing on the cake for this material.

In the market, fiber bundles formed by collecting thousands of filaments are commonly used.

These fiber bundles can be used alone, or can be woven into carbon fiber cloth, or can be composited with matrix materials such as resin, metal, and ceramics to make carbon fiber reinforced polymer (CFRP). Among them, carbon fiber reinforced polymer (CFRP) is currently the most widely used form, accounting for more than 90%.

This kind of composite material not only fully retains the core advantages of carbon fiber such as high strength, high modulus, and low density, but also has the forming convenience and corrosion resistance of the matrix materials. It is an ideal choice to replace traditional metal materials. Because of these outstanding advantages, carbon fiber is called “the king of new materials” and “black gold” by the industry, and is widely used in aerospace, automobile manufacturing, wind power energy, sports and leisure, and high-end industrial fields. It has become an irreplaceable choice.

Carbon fiber components on Formula 1 race cars

Properties of Carbon Fiber

Performance Feature	Content
Low Density	Bulk density 1.8 g/cm³. The density of carbon fiber composite is basically equivalent to magnesium and titanium, less than 1/4 of steel, and 1/2 of aluminum alloy. Using carbon fiber composite as structural material can reduce structural weight by 30%–40%.
High Tensile Strength	Tensile strength above 3500 MPa.
High Modulus	Elastic modulus above 230 GPa.
High Specific Strength	Specific strength 1900 MPa/Kg, 16 times greater than steel, 12 times greater than aluminum alloy.
Ultra-High Temperature Resistance	Under non-oxidizing atmosphere, can be used at 2000°C.
Low Temperature Resistance	At -180°C low temperature, steel becomes more brittle than glass, while carbon fiber still maintains elasticity.
Acid, Oil, and Corrosion Resistance	Carbon fiber has high pure carbon content, and carbon is one of the most stable chemical elements, causing it to withstand erosion from concentrated hydrochloric acid, phosphoric acid, and other media. Its corrosion resistance exceeds gold and platinum, while also having good oil resistance.
Low Coefficient of Thermal Expansion	Most carbon fibers have negative coefficient of thermal expansion at room temperature, zero at 200–400°C, and only 1.5×10⁻⁶/°C below 1000°C, not easily deformed due to high working temperature.
Strong Fatigue Resistance	Carbon fiber structure is stable. According to Polymer Network statistics, after millions of cycles of stress fatigue testing, its composite material still retains 60% of strength, while steel is 40%, aluminum 30%, and fiberglass only 20%–25%.

Manufacturing Process of Carbon Fiber

In the production practice of JC Autocarbon, we deeply realize: the birth of a high-quality carbon fiber is by no means simple “high-temperature firing,” but a systematic engineering involving polymer chemistry, precision spinning, and extreme heat treatment. Currently, over 90% of industrial carbon fibers originate from the Polyacrylonitrile (PAN) route. The length of its preparation chain and the narrowness of its process window constitute the core of this material’s high technical barrier.

Monomer Polymerization

Acrylonitrile → PAN

Spinning & Forming

Wet / Dry-jet Wet

Pre-oxidation

200–300°C · Air

Carbonization

1000–1500°C · Inert Gas

Graphitization

2000–3000°C · Optional

Surface Treatment

Sizing · Winding

1. Polymerization and Spinning: The Starting Point of Establishing Microscopic Order

Everything starts from the petroleum cracking product — propylene. After obtaining high-purity acrylonitrile monomer (purity needs to reach above 99.9%) through ammoxidation reaction, free radical polymerization is carried out under the action of initiator to generate polyacrylonitrile resin with controllable molecular weight.

Subsequently, the resin is dissolved in solvents such as dimethyl sulfoxide (DMSO) to form spinning solution, which is extruded and formed through wet spinning or dry-jet wet spinning process. Dry-jet wet spinning has become the mainstream technical route for high-performance carbon fiber precursor because of its higher spinning speed (can reach above 300 m/min) and more rounded and dense fiber cross-section.

The formed precursor needs to go through washing, stretching, and drying, finally obtaining white PAN precursor with diameter about 10–15 microns. This white PAN precursor is the source of carbon fiber’s high strength.

2. Pre-oxidation: The Key Transformation from Organic to Inorganic

Pre-oxidation is the most time-consuming and energy-consuming link in the entire production line, usually occupying 75%–90% of total processing time. The precursor is slowly heated to 200–300°C at a rate of 1–5°C/min under controlled tension. Oxygen in the air promotes cyclization and cross-linking of the cyano groups in the PAN molecular chain, forming heat-resistant ladder structure.

This process releases large amounts of volatile gases such as NH₃ and HCN, and the fiber color also changes from white to yellow, brown, and finally deep black.

If heating is too fast or tension is uneven, the fiber is very easy to fuse and be scrapped. The uniformity of pre-oxidation directly determines the skin-core structure ratio and mechanical consistency of the final carbon fiber, which is exactly the link that JC Autocarbon particularly values in quality control.

3. Carbonization: The Leap of Carbon Content

The pre-oxidized fiber enters a carbonization furnace filled with nitrogen protection, experiencing two stages of pyrolysis: low-temperature carbonization (400–800°C) to expel residual non-carbon elements such as hydrogen, oxygen, and nitrogen; high-temperature carbonization (1000–1500°C) further regularizes the carbon plane structure, causing carbon content to leap to above 95%.

After this step, fiber density increases from about 1.2 g/cm³ to 1.7–1.9 g/cm³, and strength obtains a qualitative leap.

4. Graphitization and Post-Treatment: The Ultimate Tuning of Performance

If high-modulus carbon fiber (elastic modulus >350 GPa) needs to be prepared, then graphitization treatment (2000–3000°C) must be carried out in argon atmosphere. High temperature promotes graphite crystallites to highly orient and arrange along the fiber axial direction, and modulus can soar to 500–600 GPa, but strength will slightly decrease.

Subsequently, the fiber undergoes electrolytic oxidation for surface roughening and functional group modification to improve interfacial bonding force with the resin matrix; finally, epoxy resin or polyurethane-type sizing agent is coated, and it is wound into a roll. At this point, the production of high-quality carbon fiber tow is completed.

Practical Applications of Carbon Fiber

Carbon fiber is rarely used alone. The more common application is the composite material system (CFRP) formed after fusing it with resin, metal, ceramic, and other materials. The strength and modulus of CFRP are both unparalleled, so its applications in various industries are extremely wide.

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Aerospace

Carbon fiber is the core weight-reducing material for commercial aircraft fuselage, wing primary load-bearing structures, and engine components. The carbon fiber usage of Boeing 787 and Airbus A350 respectively reaches 50% and 53% of the total aircraft weight. Each aircraft can reduce weight by several tons, and fuel efficiency improves by more than 20%.

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Automotive and Racing

From F1 monocoque to mass-produced supercar body structural parts, and then to electric vehicle battery pack enclosures, all use carbon fiber. Carbon fiber battery pack can reduce weight by more than 40% compared with aluminum alloy, and 10% vehicle weight reduction can bring 6%–8% range improvement.

🌬️

Wind Energy

Carbon fiber is the core material for the spar cap of hundred-meter-level wind turbine blades. Carbon fiber can make blades longer, lighter, and stiffer, significantly improving swept area and power generation efficiency, and has become the standard configuration for offshore large-megawatt units.

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Sports and Leisure

Carbon fiber material can reduce golf club weight by nearly 50%, and bicycle frame weight by nearly 40%. Tennis rackets, fishing rods, skis, and other products using carbon fiber can also obtain lighter hand feel and more precise body feeling.

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Medical and Health

Carbon fiber has excellent X-ray penetrability (almost does not absorb rays), so it is widely used for CT bed plates, surgical instruments, and orthopedic implant brackets. PEEK-based thermoplastic carbon fiber also has good biocompatibility.

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Hydrogen Energy and Industry

Carbon fiber is the core winding layer material for Type IV hydrogen storage cylinders. It can ensure safe hydrogen storage and transportation under 70 MPa high pressure. It is also applied to robotic arms, drones, precision instrument brackets, and other scenarios with extreme requirements for stiffness and weight reduction.

Comparison of Carbon Fiber with Other Materials

At the material selection stage, the question customers ask most often is: “How much better is carbon fiber than the steel/aluminum/fiberglass I am currently using?” The answer cannot be generalized, but data does not lie. The table below systematically compares Carbon Fiber Reinforced Polymer (CFRP) with traditional metal materials and fiberglass from the perspective of key engineering indicators.

Comparison Dimension	Carbon Fiber (CFRP)	High-Strength Steel	Aluminum Alloy (6061-T6)	Titanium Alloy (TC4)	Glass Fiber (GFRP)
Density (g/cm³)	1.5–1.65	7.85	2.70	4.5	2.0
Tensile Strength (MPa)	1500–2800+	980–1080	310	960	1500
Specific Strength (×10⁴)	10–18+	1.3	1.15	2.1	4.8
Elastic Modulus (GPa)	230–600	210	69	114	42
Specific Modulus (×10⁶)	8.6–24	2.6	2.6	2.5	2.1
Thermal Expansion Coefficient (10⁻⁶/°C)	−1.2 ~ 1.0 (Designable)	12	23.6	8.6	5–7
Fatigue Resistance	Excellent	General	General	Good	Good
Corrosion Resistance	Excellent (No Coating Needed)	Needs Galvanizing / E-coating	Needs Anodizing	Excellent	Excellent
Material Unit Price	High	Low	Medium	High	Low
Typical Weight Reduction Potential vs Steel	50–70%	—	30–50%	40–50%	25–40%
Recyclability	Recyclable but High Energy Consumption	Fully Recyclable	Fully Recyclable	Fully Recyclable	Recyclable

How to Read This Table?

From the table it can be seen that carbon fiber crushes other metal materials in strength and modulus. For example, if a car’s structural parts are completely replaced from steel to carbon fiber, then the weight of this car can almost be reduced by half, and the body strength does not decrease but instead increases.

However, carbon fiber is also not suitable for all situations. Its anisotropy means that mechanical properties highly depend on the fiber layup direction; transverse and interlaminar shear strength are far lower than axial tensile strength, which needs to be compensated through precise layup design.

In addition, the brittle failure mode of carbon fiber (fracture without plastic deformation warning) and the lightning strike protection and galvanic corrosion problems brought by conductivity also require engineers to take them into consideration at the design stage.

In the customization process of JC Autocarbon, we always advise customers to adopt a “scenario matching” mindset: for load-bearing parts that are extremely cost-sensitive and have simple shapes, steel, aluminum, or composite parts combining metal with carbon fiber are more practical choices; for high-end structures pursuing extreme weight reduction, high fatigue life, or complex curved surfaces, the advantage of carbon fiber is irreplaceable.

FAQ

This question needs to distinguish between “absolute strength” and “specific strength.” In terms of absolute tensile strength, high-end carbon fiber (2800 MPa grade) is indeed superior to most structural steel (about 1000 MPa); but what really makes carbon fiber stand out is its huge advantage in specific strength (strength/density) — which can reach 5–10 times that of steel. That is to say, if carbon fiber is used to make a structure with the same load-bearing capacity as a steel part, its weight is only 1/5 to 1/4 of the steel part.

However, it should be noted that the interlaminar shear strength and transverse strength of carbon fiber are far lower than the axial direction, so reasonable layup and structural form must be coordinated in design.

The high price of carbon fiber originates from three factors: complex process (dozens of steps in the entire process, with pre-oxidation energy consumption accounting for 70%), expensive equipment (huge investment in high-temperature carbonization furnaces and graphitization furnaces), and limited scale (compared with steel annual production of several billion tons, global carbon fiber annual capacity is only about 200,000 tons level).

In addition, aerospace-grade carbon fiber also needs to pass strict certification cycles, further pushing up the threshold.

Future price trends depend on two variables: first, the continued advancement of large tow (≥48K) and domestic production, which is expected to reduce industrial-grade carbon fiber prices by 30%–40%; second, the industrialization of recycled carbon fiber (rCF).

Although recycled carbon fiber from retired wind turbine blades has decreased strength, it already has economic viability for use in non-load-bearing automotive parts. JC Autocarbon judges that in the next three to five years, industrial-grade carbon fiber prices will show a trend of stable with slight decline.

Surface damage (such as surface scratches, slight delamination) can usually be repaired through grinding, patching, and secondary curing; but deep structural damage (large-area delamination, fiber breakage) has low repair value, because the mechanical properties of the repaired area are difficult to restore to original level, and professional equipment and process verification are required.

In JC Autocarbon’s recommendation, preventive design is more important than post-damage repair. For example, in automotive applications, we will add local reinforcement layers in high-impact-risk areas, or adopt replaceable modular design for vulnerable parts.

The recycling of traditional thermosetting carbon fiber composites does indeed face challenges, because the cured epoxy resin forms a three-dimensional cross-linked network, which cannot be simply remelted and remolded like thermoplastic plastics. Currently mainstream recycling paths include pyrolysis recycling (high-temperature decomposition of resin, recovering chopped carbon fiber) and mechanical crushing (grinding into filler-grade powder).

The mechanical properties of recycled carbon fiber are about 70%–80% of virgin fiber, suitable for non-load-bearing parts.

What is more worth looking forward to is the rise of thermoplastic carbon fiber composites — because the matrix resin can be repeatedly melted and formed, its recycling rate is far higher than the thermosetting system. JC Autocarbon is actively laying out thermoplastic carbon fiber product lines to respond to the long-term demand of global manufacturing for green and low-carbon materials.

The fundamental difference between the two lies in the chemical nature of the matrix resin:

Thermosetting carbon fiber: mainly uses epoxy resin, forming an irreversible three-dimensional network structure after curing, with high temperature resistance (about 160–180°C) and high bonding strength. It is currently the absolute mainstream in the market (accounting for >90%). The disadvantages are non-remoldability, difficult recycling, and longer molding cycle (several minutes to several hours).
Thermoplastic carbon fiber: uses thermoplastic resins such as PEEK, PPS, and PA as matrix, which can be repeatedly heated to soften and cooled to harden. The advantages are higher impact resistance (can reach 10 times that of thermosetting), faster molding speed (seconds level), and recyclable reuse. PEEK matrix also has excellent biocompatibility, suitable for medical implant scenarios.

At this stage, thermosetting carbon fiber is still the winner in terms of cost and maturity, but thermoplastic carbon fiber shows huge potential in the direction of high performance, large volume, and recyclability.

The core bottleneck lies in the triple constraints of cost, takt time, and repair system. Stamped steel sheet production takt time is calculated in seconds, while carbon fiber compression molding usually takes several minutes; a set of steel stamping line investment is about 10–25 million USD, while for carbon fiber, when annual production is below 50,000–100,000 units, mold cost (3–8 million USD) actually has more advantage.

In addition, the brittle failure characteristic of carbon fiber means that collision repair requires professional technicians and specialized equipment, which the traditional 4S shop system is difficult to undertake.

Therefore, current carbon fiber application in the automotive field follows the “key parts first” strategy: body monocoque, hood, roof, battery pack enclosure, etc. Replacing these parts with carbon fiber can maximize benefits, and they can tolerate relatively longer production cycles.

There are a large number of “fake carbon fiber” products on the market. Common identification methods include:

Water transfer printing sticker: only has carbon fiber texture on the surface, with plastic underneath. The knocking sound is dull, with no fiber layer sense.
Chopped fiber / low-content products: short fiber length, low content (<30%), mechanical performance is vastly different from real continuous fiber composite materials.
Genuine features: continuous fiber products show clear woven texture or unidirectional tape traces, cross-section presents layered structure of fiber and resin, knocking sound is crisp, weight is extremely light but rigidity is extremely high.

For details, please check the article: How to Tell Dry Carbon and Wet Carbon?

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Author: He Dong

He Dong – Automotive & Motorcycle Engineering Specialist, has spent 20+ years doing what he loves most — making cars and bikes faster, sharper, and better looking.