A new composite curing technology that uses high energy electron beams is set to allow composite materials to take centre stage in the development of new aerospace vehicles, such as the proposed Joint Strike Fighter (JSF) aircraft and the Space Shuttle replacement, Venture Star. The next generation of aircraft could have entire wings built from a single moulding of high-tech composite materials that will be stronger and lighter than many of the traditional materials used today.
Electron beam curing, say researchers at Acsion Industries in Manitoba, Canada, could have a massive impact in the aerospace and defence industries helping reduce production costs significantly, speeding up processing times and offering better material properties in the finished products. Vince Lopata, director of operations at Acsion, says, "Eight independent studies have shown potential manufacturing cost savings of 26-65 per cent [and] for prototyping alone, this could rise to as much as 90-95 per cent."
Composite materials are made by lacing together two or more different materials to gain the benefits of both. The plastic resins most commonly used in aerospace composites need to be 'cured' in order for the composite to form properly. Traditionally this curing process involves 'cooking' the product in a high temperature and high pressure autoclave. Electron beam curing works by firing an electron beam at the part. The incoming high speed electrons knock off other electrons in the polymer resin causing the material to cure. X-rays generated from the high energy beams can penetrate even deeper into the composite, giving a uniform cure to material several centimetres thick. Because electron beam processing takes minutes as opposed to hours for traditional autoclave thermal curing, says Lopata, the process offers a much faster throughput. Electron beam curing has the added advantage of being fully portable and has been successfully used by Air Canada for on-runway repairs to one of their A320 passenger aircraft.
Acsion are currently working with Lockheed Martin in developing the airframe for the JSF. The plane would be constructed from up to 95 per cent composite materials and be built from far fewer parts than normal, perhaps as few as 500 compared to 2,500, according to Lopata. The curing technique could also offer a great deal to the further development of the Venture Star spacecraft. The Venture Star (or X-33) has large cryogenic tanks (30m by 16m) that store liquid oxygen and hydrogen at -200 to -255 degrees Celsius. Electron beam curing not only overcomes the problem of finding an autoclave big enough to accommodate these huge composite tanks, it also overcomes the residual stresses caused by the tanks being made in an autoclave (at up to 120 - 200 degrees Celsius) and then being used at well below freezing for the storage of the liquid gases.
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Notes For Editors
1. This item is due to appear as "A beaming outlook for composites processing"
by Steve Hill, in the July issue of Materials World, Volume 7, Issue 7, p.398.
2. Materials World is the journal of The Institute of Materials, the
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