Overview of Carbon Fiber Reinforced Polymer (CFRP) Composites

Carbon Fiber Reinforced Polymer (CFRP) composites are highly engineered materials known for their high specific modulus and high specific strength. These properties make them ideal for applications requiring high strength, stiffness, low weight, and excellent fatigue characteristics. Compared to aluminum and steel, the specific strength of carbon fibers is approximately ten times higher, depending on the fiber used. Over the past fifty years, CFRP has found successful applications in aerospace, automotive, rail transportation, marine, and wind energy industries. In the past twenty years, CFRP has seen a global compound annual growth rate (CAGR) of about 12.5%. In the aerospace sector, the recent long-range aircraft models, Airbus A350 and Boeing 787, use CFRP extensively in their airframe structures, accounting for more than 50% of their weight. In automotive structures, such as body panels, roofs, and floor components, the need for stiffness makes carbon fiber advantageous for reducing vehicle weight and enhancing performance. In wind turbine applications, carbon fiber’s higher specific modulus compared to E-glass fibers allows for longer and more aerodynamically efficient blades. The use of composite pressure vessels for lightweight fuel storage is also rapidly growing.

Stringent global CO2 emission standards and current carbon neutrality regulations are expected to have a profound impact on the carbon fiber composites industry. Lightweight composites are crucial in renewable energy fields such as wind energy, photovoltaics, and hydrogen energy, addressing broad requirements in protection, storage, transportation, and usage.

This article reviews the history of carbon fiber and carbon fiber composites, the current global development and production of CFRP, and trends in its application across various sectors, including aerospace, wind turbines, automotive, pressure vessels, sports and leisure, and construction. It discusses the significance of new carbon fiber composite developments from emerging materials (like large tow carbon fibers and thermoplastic matrices), manufacturing processes (such as cost-effective out-of-autoclave production and liquid molding for cost reduction and increased output), and the urgent need for recycling and reusing composites.

History of Carbon Fiber and Carbon Fiber Composites

Early Development

The early development of carbon fiber and carbon fiber composites spans the 1950s and 1960s. Carbon fibers, with a diameter of 5–10μm, exhibit high specific strength, high specific modulus, high chemical resistance, thermal stability, and low thermal expansion. In 1958, Roger Bacon from Union Carbide Corporation in the United States accidentally produced carbon fibers while heating rayon in an argon atmosphere. In 1960, Richard Millington from H.I. Thompson Fiber Glass Company developed a method to increase the carbon content of rayon-based fibers to 99wt% and patented it. Around the same time, researchers in Japan and the UK began developing carbon fibers using polyacrylonitrile (PAN) instead of rayon. PAN, a synthetic semi-crystalline organic polymer resin, became an economic choice due to its higher carbon yield and simpler manufacturing process. In 1961, Toray Industries in Japan showed interest in PAN carbon fiber technology and established a pilot production in 1964. In the late 1960s, Toray signed a licensing agreement for the PAN process.

During this period, the UK’s Royal Aircraft Establishment also patented a PAN-based carbon fiber manufacturing process, leading to stronger carbon fibers than previous methods. This process was licensed to companies like Rolls-Royce, Morganite, and Courtaulds. Rolls-Royce began using carbon fibers for jet engine components, notably the RB-211 engine with carbon fiber composite compressor blades. Despite initial setbacks due to bird strikes, the technology saw continued development. By the late 1960s, Japanese and UK companies led the laboratory development of carbon fiber production, while US companies like DuPont and Union Carbide experimented with acrylic or rayon-based carbon fibers.

The Beginning of the Carbon Fiber Composite Industry

The carbon fiber composite industry began to take shape between the 1970s and 1980s. In 1970, Toray Industries and Union Carbide formed a joint venture, leading to the maturation of PAN-based carbon fiber production. By 1971, Toray had established a 12-ton carbon fiber production capacity and started producing Torayca®300 (T300). In 1972, Toray launched its first commercial carbon fiber composite product, fishing rods, reducing the weight of existing products by about 50%. By the late 1970s, companies like Hercules in the US adopted carbonization technology for commercial production.

The 1980s saw the industrialization of carbon fiber production, with Toray developing a wide range of products like T300, T800, and T1000. By 1988, Torayca® carbon fibers had achieved a cumulative production of over 100,000 tons, widely used in aircraft components. During this period, the UK transferred technology to the US, China, India, Russia, and Brazil, further expanding global production capabilities. The industrial manufacturers Zoltek in the US and Formosa in Taiwan also emerged, highlighting the growing global footprint of carbon fiber production.

The First Wave of Carbon Fiber Composite Applications: Aerospace

The first wave of carbon fiber composite applications spanned the 1990s to the 2000s. This period saw significant mergers and acquisitions among carbon fiber manufacturers. For example, Torayca® CFRP prepreg was adopted by Boeing for the main structure of the Boeing 777. Companies like Hexcel acquired Hercules' carbon fiber division, and major players like Amoco joined forces with Japanese companies for joint ventures. By 2001, these assets had changed ownership and rebranded as Cytec.

The Boeing 787 project, launched in 2003, marked a milestone with CFRP accounting for 50% of the aircraft's weight. This extensive use of CFRP reduced the aluminum percentage from 77% to 20%, significantly reducing weight and fuel consumption. Similarly, Airbus’s A350 XWB program, launched in 2005, also extensively used CFRP, demonstrating a shift towards composite materials in commercial aviation. These advancements significantly increased the use of CFRP in aerospace, driven by demands for lower fuel consumption, reduced CO2 emissions, and lower maintenance costs.

The Second Wave of Carbon Fiber Composite Applications: Industrial Use

The second wave of carbon fiber composite applications began in the 2010s, characterized by rapid expansion into non-aerospace industrial uses. This wave saw carbon fiber applications in wind energy, automotive, rail transportation, and civil infrastructure. For instance, Zoltek’s partnership with Vestas in 2007 led to the widespread use of carbon fiber in wind turbine blades, reducing blade weight by 38% and increasing efficiency.

In the automotive industry, the collaboration between BMW and SGL in 2010 aimed to provide carbon fiber for lightweight electric vehicles, highlighting the sector’s potential. By 2017, SGL had acquired BMW's stake, marking significant growth in carbon fiber use in electric vehicles. The advancement of large tow carbon fibers and improved manufacturing processes further reduced production costs, making carbon fiber more accessible for industrial applications.

Trends in CFRP Development and Production

Global CFRP demand has steadily increased since 2014, with an estimated consumption of 181,000 tons in 2021 and a projected demand of 285,000 tons by 2025. Wind energy accounted for a significant portion of this demand, with substantial growth observed in the automotive and pressure vessel sectors. Despite the pandemic, the sports and leisure market remained stable, with growing applications in electric vehicles and hydrogen storage pressure vessels.

By 2021, China had become the largest market for CFRP, reflecting a shift in global consumption patterns. Europe also saw substantial consumption, driven by the automotive and wind energy sectors. Manufacturing processes such as filament winding and pultrusion emerged as dominant methods, surpassing traditional prepreg and lay-up processes.

Challenges and Future Prospects

Despite advancements, several challenges remain in CFRP applications, including cost reduction, recycling, and standardization of recycled materials. The development of large tow carbon fibers and thermoplastic matrix composites shows promise in addressing these challenges, making CFRP more competitive and sustainable.