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MATERIALS I COMPOSITES
Quick, quick, slow: At Mach 0.925 the G650 will be the fastest civil aircraft around; the development of its structural manufacturing technology has been slower to mature
It’s thermo-dynamic! F
Winning an Innovation Award at JEC Composites was the icing on the cake for Fokker Aerostructures’ development team. As Dr Neil Calder discovers, the roots of this innovation go much deeper into the development of the portfolio of design and manufacturing capabilities for the new Gulfstream G650.
okker manufactures the body panels, floor and the tail structure for the Gulfstream G650. Its first flight was in November 2009 and is expected to achieve certification
within two years. At Mach 0.925 it will be the fastest civil aircraft in the sky, but the development of the manufacturing technology that makes its structure special has been a bit slower to mature. With the G650 vertical tail rudder and horizontal tail
control surfaces, Fokker has replaced assemblies of thermoset composites and aluminium with more monolithic structures using induction welded thermoplastics. The novel material component of this is Ticona’s Fortron polyphenylene sulphide (PPS) resin, which is pre-impregnated into carbon fibres by TenCate and has now been qualified for use in aircraft primary structures – the first time thermoplastics have been used in this way. Fokker reports 10% weight reduction and 20% cost reduction for these tail structures compared with alternative processing routes.
There is a strong current trend towards a greater use of thermoplastics in high performance composites structures, driven by considerations of mass reduction as well as tackling
issues of sustainability and recyclability. Thermoplastic composites are already well-established within aircraft interiors but airframe components in primary structure from this class of material are just emerging. This progression of thermoplastic resins from secondary to primary structure is opening up the design and manufacturing envelope with a new set of production characteristics.
There are numerous engineering reasons why thermoplastic
composites are attractive as aerostructures, such as increased toughness compared with thermosetting alternatives and inherent flame retardancy. Because the processes of material consolidation and forming don’t involve exothermic curing reactions they can use shorter autoclave cycle times, although the temperatures involved are generally higher than those for thermosets. The meltability of the material also provides better potential for recycling. The composite materials used by the Fokker-led team are
a new generation of carbon/PPS semipregs. Instead of being impregnated with resin films as is more usual, these fibre- reinforced thermoplastic materials are made using a powder coating process. PPS powder is directly applied and fused to
©Gulfstream Aerospace Corporation
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