CARBON FIBER

Name: Carbon Fiber (carbon-based composite material, C)

Symbol: C (main component)

Group: 14 (for elemental carbon)

Period: 2 (for elemental carbon)

Block: p (for elemental carbon)

Category: Composite material (not a pure allotrope, but carbon-reinforced polymers)

Atomic number: 6 (for elemental carbon)

Atomic mass: 12.011 u (per carbon atom)

Electrons per shell: 2.4 (per carbon atom)

Electronegativity: 2.55 (for carbon)

Density: 1.75–2.0 g/cm³ (depends on fiber type and matrix)

Melting point: Not defined (decomposes ~3,500–4,000 °C in an inert atmosphere)

Boiling point: Not applicable (decomposes before sublimate)

Thermal conductivity: 20–100 W/(m K) (anisotropic, varies with fiber orientation)

Electrical conductivity: ~10⁴–10⁵ S/m (moderate, depends on the structure)

Magnetic order: Diamagnetic

Ordinary state: Solid (composite of fibers in a polymer matrix)

Oxidation states: 0 (mainly), +2, +4 (in derived compounds)

Mohs hardness: Not applicable (composite material, non-homogeneous)

Vickers hardness: ~1,500–3,000 MPa (depends on the matrix and reinforcement)

Brinell hardness: Non-standard (composite material)

Most stable isotopes: C-12 (98.93%), C-13 (1.07%)

Discoverer: Not attributed to an individual; developed in the 1950s–1960s (pioneering research by Roger Bacon and Union Carbide, USA)

Carbon fiber, a composite material composed of carbon (C) fibers embedded in a polymer matrix, usually epoxy resin, is known for its high mechanical strength (~3–7 GPa), light weight (density of 1.75–2.0 g/cm³), and moderate thermal conductivity (20–100 W/(m·K)). Although carbon, with an abundance of ~200 ppm in the Earth's crust, has been used since ancient times in forms such as graphite and charcoal, carbon fiber is a modern development that emerged in the 20th century to meet the demands of industries such as aerospace, automotive, and sports. Its history reflects advances in materials science, driven by the need to create lightweight and strong structures, and has transformed key sectors with applications ranging from aircraft to medical equipment. The origins of carbon fiber date back to the late 19th century, when Thomas Edison experimented with carbon filaments for incandescent light bulbs in 1879 by carbonizing cellulose fibers. However, modern carbon fiber development began in the 1950s, driven by the Space Race and the Cold War. In 1958, Roger Bacon, working at Union Carbide (USA), produced the first high-strength carbon fibers by heating rayon (a cellulose polymer) under controlled conditions, obtaining filaments with a partially graphitic structure (sp² hybridization). Although these fibers were strong, they were expensive to produce and their performance was limited, which restricted their initial use.

The breakthrough came in the 1960s, when researchers in the UK, Japan, and the US perfected manufacturing processes using more efficient precursors, such as polyacrylonitrile (PAN) and coal tar. In 1963, scientists at the Royal Aircraft Establishment (RAE) in the UK, led by William Watt and Leslie Phillips, developed a method for the controlled pyrolysis of PAN at temperatures of ~1,000–2,500 °C in inert atmospheres (such as nitrogen, N₂), producing carbon fibers with high strength and elastic modulus. This process, still used today, enabled the commercial production of carbon fibers, which were soon adopted in the aerospace industry for aircraft components such as wings and fuselages due to their superior strength-to-weight ratio to steel (up to 10 times stronger per unit weight).

In the following decades, carbon fiber expanded to other industries. In the 1970s, the automotive industry began incorporating carbon fiber composites into high-performance vehicles, such as Formula 1 cars, to reduce weight and improve safety. In the 1980s, its use in sporting goods, such as tennis rackets, bicycles, and golf clubs, popularized the material among consumers. Currently, global carbon fiber production (150,000 tons per year by 2025) is dominated by manufacturers such as Toray (Japan) and Hexcel (USA), with a market value of approximately USD 10 billion. Applications include aerospace structures (e.g., the Boeing 787, with approximately 50% carbon fiber), medical prosthetics, wind turbines, and electronics (conductive housings). Although production costs (USD 10–50/kg) have decreased, synthesis remains energy-intensive, limiting its widespread use. The history of carbon fiber, from Edison's experiments to its ubiquity in modern technology, illustrates how materials innovation can transform industries and redefine the boundaries of engineering.

Carbon fiber is a composite material composed of sp² hybridized carbon (C) filaments arranged in a graphitic structure and embedded in a polymeric matrix, typically epoxy resin, which gives it an exceptional combination of strength, lightness, and durability. With a density of 1.75–2.0 g/cm³, it is significantly lighter than steel (7.8 g/cm³) and aluminum (2.7 g/cm³), while its tensile strength (3–7 GPa) and elastic modulus (200–600 GPa) exceed those of traditional metals, offering a strength-to-weight ratio up to 10 times higher. Produced by pyrolysis of precursors such as polyacrylonitrile (PAN) at temperatures of 1,000–2,500°C in inert atmospheres (such as nitrogen, N₂), carbon fiber is not a pure allotrope of carbon, but an engineered material that takes advantage of the abundance of carbon (~200 ppm in the Earth's crust) for applications in high-performance industries such as aerospace, automotive, and medical.

Physically, carbon fiber stands out for its high mechanical strength and stiffness, determined by fiber orientation and matrix quality. The fibers, with diameters of 5–10 µm, are composed of aligned graphitic laminae, making them anisotropic: their strength is greatest along the fiber direction, but lowest in perpendicular directions. Its thermal conductivity (20–100 W/(m K)) is moderate, useful for heat dissipation in electronic or aerospace components, while its electrical conductivity (~10⁴–10⁵ S/m) allows for applications in conductive housings. Carbon fiber is thermally stable up to ~3,500–4,000 °C in inert atmospheres, but decomposes in the presence of oxygen (O₂) at temperatures above 400 °C. Its corrosion resistance is notable, being immune to mild acids, bases, and humid environments, although it can degrade under prolonged exposure to strong oxidizing agents such as nitric acid (HNO₃).

Chemically, carbon fiber is inert under standard conditions, thanks to the stability of its sp² bonds and the protection of the polymer matrix, making it suitable for corrosive environments in applications such as wind turbines or chemical equipment. Its low density and high fatigue resistance make it an ideal material for structures that require durability without additional weight, such as aircraft fuselages (e.g., the Boeing 787, 50% carbon fiber) or racing car chassis. Although it is not inherently biocompatible, it can be modified for medical applications, such as prosthetics. Global production (150,000 tons by 2025) and costs (~$10–$50/kg) reflect the energy intensity of its manufacture, but its versatility in aerospace, automotive, sports, and energy (turbines, batteries) cements it as a key material in modern engineering, combining the properties of carbon with an optimized design for high-performance applications.

Carbon fiber, a composite material composed of sp² hybridized carbon (C) filaments embedded in a polymer matrix, usually epoxy resin, is valued for its high tensile strength (3–7 GPa), light weight (density 1.75–2.0 g/cm³), and corrosion resistance, making it ideal for high-performance applications. With thermal conductivities of 20–100 W/(m K) and electrical conductivities of ~10⁴–10⁵ S/m, along with thermal stability up to ~3,500–4,000 °C in inert atmospheres (such as nitrogen, N₂), carbon fiber combines the properties of carbon with optimized structural design. Global production (150,000 tons per year by 2025) and a market of approximately USD 10 billion reflect its importance in industries such as aerospace, automotive, sports, and energy, where its strength-to-weight ratio, up to 10 times higher than steel, transforms product design and efficiency.

Carbon fiber's primary use is in the aerospace industry, where its lightness and strength allow for the construction of aircraft structural components such as fuselages, wings, and empennages. For example, the Boeing 787 Dreamliner uses approximately 50% carbon fiber in its structure, reducing weight by approximately 20% compared to traditional materials such as aluminum (Al), which improves fuel efficiency. In the automotive industry, carbon fiber is used in high-performance vehicles, such as Formula 1 cars, and in luxury cars (e.g., Lamborghini or BMW i-Series chassis), where it reduces weight and increases collision safety due to its high energy absorption. It is also used in electric vehicles to offset the weight of lithium-ion (Li-ion) batteries. 

In the sports industry, carbon fiber is ubiquitous in equipment such as racing bicycles, tennis rackets, golf clubs, and fishing rods, where its stiffness and low weight (~1.8 g/cm³ versus ~7.8 g/cm³ for steel) improve performance. In energy, it is used in wind turbine blades, which require lightweight and durable materials to withstand dynamic loads, and in battery and supercapacitor housings, taking advantage of its electrical conductivity. In medicine, carbon fiber is used in prosthetics and diagnostic equipment (such as X-ray plates), as it is radiolucent and allows clear images without interference. 

In the maritime and construction industries, it is used in boat hulls and structural reinforcements, resisting corrosion from saltwater and humid environments better than traditional metals. Although production costs (~10–50 USD/kg) and the energy intensity of pyrolysis of precursors such as polyacrylonitrile (PAN) limit its widespread adoption, advances in recycling and more efficient manufacturing methods are expanding its accessibility. Carbon fiber, with its ability to combine strength, lightness, and chemical stability (immune to mild acids and bases), continues to redefine standards in engineering, from aircraft and automobiles to medical and sports applications, establishing itself as a key material in modern technology.