LHT moves forward with new composite repair technique

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Lufthansa Technik (LHT) has submitted a patent application for a largely automated composite repair process it has been developing with EADS subsidiaries Cassidian and Eurocopter, for use on fuselage and wing structures as well as helicopter rotor blades.

The maintenance provider has been working for some time on a method to repair damaged carbon composite airframe components by replacing the broken fibres instead of covering them with a repair patch. While this is already possible for secondary airframe structures, damaged primary structural components need to be fixed through doubler repairs with either composite or titanium patches, which add weight.

The central step forward was to automate the repair process to achieve replicable, reliable results - and a 60% reduction in repair time, said LHT technology projects director Franz-Josef Kirschfink.

The team developed a largely automated system for the different steps of the repair process. The damaged area is initially scanned with an accuracy of 0.01mm, using strip-light projection. Computer-controlled milling machines then remove the damaged material and produce an exact replacement, which can be inserted, bonded and cured.

So far, the system has been designed as stationary equipment for use at a maintenance base, but LHT hopes to develop a mobile system for use in aircraft-on-ground situations by 2015.

The work, supported in part by German government research funding, also called on inputs from Braunschweig-based GOM, which specialises in three-dimensional optical measuring techniques; robot design company iSAM in Mülheim; and laser-sintering firm Electro Optical Systems in Munich.