The Component Design and Manufacturing Technologies Department works on new material-specific concepts to efficiently repair fibre-reinforced polymers (FRPs), which are increasingly being used in components for aircraft and vehicle manufacturing, and for eliminating manufacturing errors. Due to new process technology solutions, techniques to digitally optimise the repair geometry and, at the same time, make the repair increasingly time- and cost-effective, as well as more precise and reproducible have arisen. The aim is to avoid the premature disposal of FRP components and minimize waste during production. This makes FRP components more competitive, cost-effective and resource efficient.
When repairing FRP structures, the damaged layers are first removed and a patch with several single layers or cured repair section are applied. Nearly all repair techniques require heat sources to cure either the entire patch or the adhesive layer through a heating cycle.
The repair concept that has been developed uses inductively heated metal pressure elements: an induction coil is used to generate an alternating electromagnetic field that heats a metal plate. This is then pressed onto the patch by using vacuum bagging. The patch is then bonded to the surrounding structure under pressure and temperature.
This new repair technology offers more flexibility during integration of the patch than standard techniques. Using ovens or autoclaves, the entire part will be heated up. Heating blankets, infrared lights or heated air systems offer the possibility of heating only local parts of the structure, but are not specifically targeted to the specific area to be repaired. The inductively heated metal pressure element, on the other hand, can be adapted to the different geometrical dimensions of the area to be repaired.
A mobile repair station has been developed that includes all the systems required for repairing FRP structures. In addition to the equipment for inductive heating of the metal sheet, it has a vacuum pump (for generating) to generate the required pressure on the patch. The individual processes can be controlled from a netbook using resistance thermometers and flow meters.