Lighter than aluminium and stronger than iron, carbon fibre reinforced plastic (CFRP) is a revolutionary material that has changed new-generation manufacturing by finding its way into applications such as major structural parts for commercial passenger jets. It was in the early 1960s that research on carbon fibre started in Japan. We interviewed Shunsaku Noda, General Manager, and Hiroshi Taiko, Deputy General Manager of the Aerospace Technology Section, ACM Technology Department, TORAY, about the fifty-year history of carbon fibre and CFRP development.
CFRP is a composite of carbon fibre and resin. Composite materials contain several ingredients to create reinforced properties that cannot be realised with a single ingredient. TORAYCA® Prepreg is used for aircraft parts. It is made by shaping a bundle of 24,000, 5 μm thick carbon fibres into a sheet and impregnating it with thermoset resin such as epoxy. Layering and hardening this sheet creates high strength and a modulus of carbon fibre elasticity.
CFRP performance tends to change significantly according to the volume and layout of the carbon fibres (direction of the fibres, structure of the prepreg layers). Therefore, it is possible to realise a wide range of features by designing for individual purposes.
• It is light and has a specific gravity of 1.7, just one-quarter that of iron.
• The tensile strength of CFRP is as high as 7 Gpa.
• Tensile elasticity of high-intensity CFRP is as high as 630 Gpa
• It also features excellent dimensional stability, vibration damping, high thermal conductivity, non-magnetic, corrosion resistance and high fatigue strength.
Carbon Fiber Manufacturing Processes
PAN (polyacrylonitrile)-based carbon fibre manufacturing comprises four processes:
1) Polyacrylonitrile plastic is processed and pumped through a spinning machine to be made into fibres.
2) The fibres are heat treated to enhance flame resistance (oxidation).
3) The fibres are heated again to carbonize them.
4) The surface is treated to complete the process.
Going back to the roots of carbon fibre development, we find the light bulb invented by Thomas Edison and Joseph Swan at the end of the 19th century. The filament used for this light bulb was made of carbonized bamboo fibre. This was the world’s first carbon fibre. As tungsten became popular as material for the filament, carbon fibre was gradually forgotten. In the 1950s, carbon fibre attracted renewed attention when the United States accelerated research and development for injector tips for rockets, engines that require high heat-resistance.
Meanwhile, in 1959, Dr. Akio Shindo at the Osaka Engineering and Technology Institute invented a method of carbon-fibre manufacturing through the carbonization of polyacrylonitrile (PAN). Since then, carbon-fibre research and development and commercialisation accelerated. Carbon fibre has great strength, making it ideal as a highly-functional ingredient for composite materials.
In 1967, Rolls-Royce, one of the world’s top aerospace engine manufacturers, announced the application of CFRP to jet engines. Almost simultaneously TORAY started full-scale development of carbon fibre utilising an acrylic fibre, TORAYLONTM. In 1970, TORAY acquired a patent license from Dr. Shindo. Companies manage business based on forecasts of the future marketability and sales potential of their own products. TORAY believed in the potential of CFRP and prioritised the setting up of a manufacturing system with a bold investment that would nowadays be an unthinkable amount.
The following year, 1971, TORAY started the manufacture and sales of TORAYCA®300, PAN-based high-intensity carbon fibre. Although carbon fibre attracted attention as a new-generation material, its main uses had not yet been clarified. TORAY, however, decided to build a new plant with a 12-ton manufacturing capacity, the largest in the world at the time. This resolute decision was based on the belief among TORAY employees that high-strength materials would someday be in great demand. Top management also had a dream of a black aircraft flying through the air, aircraft made mostly of CFRP. It was around the time that Rolls-Royce was experiencing great difficulty in its development of a jet engine using some CFRP.
Meanwhile, TORAY’s first commercialised product made of carbon fibre was fishing poles, a product launched in 1972. The weight of the fishing poles was about a half that of existing types; and while relatively expensive, their performance was highly regarded in the market. In the same year, golf pro Gay Brewer Jr. used black shaft clubs made of CFRP to win the Taiheiyo Masters tournament. The recognition of the black shaft golf clubs quickly spread, and golfers rushed to purchase them. After that, CFRP was also used in the manufacture of tennis rackets, further increasing its popularity. However, CFRP was mainly finding application in entertainment and sports. Considering the industrial potential of CFRP, distribution was low at best.
A turning point came in 1975. The oil crisis that hit in 1973 forced aircraft manufacturers to prioritise the reduction of airframe weight to help realise lower fuel consumption. This turned their attention to CFRP for secondary structural material, parts that have no direct influence on flight safety. It was then that TORAY’s dream of seeing CFRP applied to aircraft manufacturing was realised. Along with the application of CFRP to aircraft parts by Boeing and Airbus, the cumulative production of TORAYCA® carbon fibre had exceeded 10,000 tons by 1988. Many overseas manufacturers in countries such as England and the United States determined to withdraw from CFRP business due to low profitability; however, Japanese companies that had passed down their technology from a long-term perspective, including TORAY, continued working on the development and manufacture of CFRP utilising high-performance carbon fibres. In 2010, Japanese carbon fibre manufacturers finally accounted for approximately 70% of the global share.
In 1990, TORAYCA® Prepreg (sheet-type CFRP) was adopted by Boeing as primary airframe structural material (important parts that directly impact safety), which served as approval for CFRP as a highly-reliable, highly-functional material. CFRP tensile strength is more than 10 times greater than iron while its weight is just one quarter. CFRP can also be formed into a wide range of shapes.
In the Boeing 787 project launched in 2003, CFRP accounts for about 50% of the total weight of the aircraft, including the frame and wings. In 2006, TORAY and Boeing entered into a long-term comprehensive agreement on CFRP supply, which specified the provision of the primary structural material by TORAY.
Noda: We are very happy when the products we develop change the world for the better, changes such as reduced fuel consumption in the aerospace industry. TORAY’s CFRP has become a strategically expanding business and our mission is to further expand CFRP into a fundamental pillar of TORAY business. Compared with the maturity of metallic materials, the types, amount and applications of carbon fibre composite materials remains unknown. We believe, however, that CFRP has unlimited possibilities and we will continue to explore these possibilities to change the world for the better.
Taiko: M y boyhood love of aviation led me to a career related to aircraft and rockets. My dream as someone engaged in research and development is to someday board an airplane made of materials that I designed. The CFRP used in the manufacture of the Boeing787 was developed by senior R&D staff, and I was only involved indirectly. I hope to realise my dream some day.