Thermoplastic parts that can be welded without drilling or riveting

Until recently, primary aircraft structures were generally made from a combination of thermoset composites and aluminium. This year, however, all that changed when engineers at Netherlands-based Fokker Aerostructures announced that they had developed the world’s first induction-welded thermoplastic composite primary structures for the tail section of the new Gulfstream G650 aircraft.

The development of the composite rudder and elevator came about as the result of a co-operative effort between Fokker and a number of its key suppliers. Ticona, for example, provided its Fortron polyphenylene sulphide (PPS) thermoplastic polymer to Tencate Aerospace Composites, which used it to manufacture the carbon-fibre-based semipreg and plate materials.

From these materials, Fokker’s engineers produced ribs, skins and spars in box structures, which they then welded together to form the rudders and elevators using patented welding technology developed by Netherlands-based KVE Composites. This joins the components into an inseparable unit, eliminating costly drilling and riveting work.

Using a thermoplastic, rather than a traditional thermosetting composite, for the design of the rudder and elevator sections brought a number of advantages - according to Arnt Offringa, director of research and development at Fokker - not least of which was a reduction in both the cost and the weight of the manufactured parts.