The system, which is used to provide interim processing of the laid-up composite rear spar assembly of the Airbus 350 XWB to prevent subsequent wrinkling, was custom-designed and developed in close co-operation with GKN Aerospace engineers following initial tests at Heraeus’ Application Centre in Neston, Wirral.
GKN Aerospace has invested £170 million to create its new composite wing structures manufacturing and assembly facility. The new ‘Western Approach’ site consists of two main buildings. The first contains a composites manufacturing operation that incorporates the latest, automated high-speed, precision production technologies. The second building houses a ‘moving line’ assembly operation that uses automated, guided vehicles to move the wing structures through a series of semi-robotic work stations.
An important work package already underway at the site is the manufacture of the all-composite rear wing spars for the Airbus A350 XWB. Each of the three rear wing spars is manufactured by laying up pre-preg carbon composite tape on a mandrel and then curing the assembly in an autoclave. However, such complex lay down operations can sometimes produce wrinkling of the final surface because of voids and excess resin between plies or laminates. One proven answer to this problem is de-bulking, which involves enclosing the composite structure in a vacuum bag at various stages in its manufacture and then compacting or squeezing out of air and volatiles between plies or pre-preg laminates under moderate heat and vacuum to insure seating on the mandrel, to prevent wrinkles, and to promote adhesion.
GKN Aerospace’s engineers decided that de-bulking could provide significant benefits and asked Heraeus to carry out initial trials using infra-red emitters to provide the required heat. These were followed by on-site trials using a portable infra-red system at Western Approach and these were so successful that a prototype system was supplied. The prototype system was finally replaced by a scaled-up 465 kW production system, where each of the three heating sections now has seven controllable zones to provide precise surface heating.