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Light Weight Composites – Future of Aircraft Materials

03 Nov 2016

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Aircraft engineers have been making consistent efforts to improve upon aircraft design and its numerous key components. One of the challenges has been to keep the weight of the aircraft down by the use of new light-weight materials.

For many years, aircraft designers proposed theoretical designs that they could not build as the materials needed to construct them did not exist. In fact, a term “unobtainium” was used to identify materials that are desired but not yet available. For instance, the Space Shuttle would have proven extremely difficult, if not impossible, to build without heat-resistant ceramic tiles to protect them during re-entry. And high-speed forward-swept-wing airplanes like Grumman’s experimental X-29 or the Russian Sukhoi S-27 Berkut would not have been possible without the development of composite materials to keep their wings from bending out of shape.

Composites have been the most important materials to be adapted for aviation since the use of aluminium in the 1920s. Composites are combinations of two or more organic or inorganic components. One material serves as a “matrix,” which is the material serves that holds everything together, while the other material serves as a reinforcement, in the form of fibres embedded in the matrix. Until recently, the most common matrix materials used were “thermosetting” materials such as epoxy, bismaleimide, or polyimide. The reinforcing materials can be glass fibre, boron fibre, carbon fibre, or other more exotic mixtures.

By the 1960s, other composite materials became available, in particular boron fibre and graphite, embedded in epoxy resins. The U.S. Air Force and U.S. Navy began research into using these materials for aircraft control surfaces like ailerons and rudders. By 1981, the British Aerospace-McDonnell Douglas AV-8B Harrier flew with over 25 percent of its structure made of composite materials. It is indeed no small achievement that Tejas, the light Indian aircraft is made of composite materials that are 45% by its weight! And out of this about 25% is designed and developed at CSIR-NAL.

“The greatest value of composite materials is that they can be both lightweight and strong. The heavier an aircraft weighs, the more fuel it burns, so reducing weight is important to aeronautical engineers, says Jitendra Jadhav, CSIR- NAL Director, a constituent lab of CSIR, which had led CSIR contributions to the LCA Tejas project in the most crucial induction phase during the last two years. Over the years CSIR-NAL has developed many other critical technologies for Tejas.

Composites offer a very attractive option in modern aircraft development as they are lighter than metal and just as strong. CSIR-NAL led the national team for the composite wing development for Tejas and has pioneered the development and fabrication of complex composite structures for Tejas aircraft using innovation and cost-effective fabrication technologies.

Modern military aircraft, such as the F-22, use composites for at least a third of their structures, and some experts have predicted that future military aircraft will be more than two-thirds composite materials. LCA stands a league apart with nearly half of its weight made of composite materials that form 90% of its surface area.

The re-engineered SARAS, twin-engine, multirole light transport aircraft intended for both civilian and military service will feature carbon fibre composite (CFC) wings. It will have a pressurised cabin separator made of composite material, a novel design compared to other aircrafts, tried first time for this purpose.

{This Feature has been received from CSIR (Unit for Science Dissemination), Ministry of Science & Technology, New Delhi}.

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