LHT moves forward with new composite repair technique

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Lufthansa Technik (LHT) has submitted a patent application for the largely automated composite repair process it has been developing with EADS subsidiaries Cassidian and Eurocopter.

The German 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.

In addition to the two EADS divisions, LHT worked together with Braunschweig-based GOM, which specialises in three-dimensional optical measuring techniques, robot design company iSAM in Mühlheim and laser sintering firm Electro Optical Systems in Munich.

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

"We have succeeded in automating virtually the entire repair process chain," said Franz-Josef Kirschfink, director technology projects at LHT. He added that this should cut repair times by up to 60% compared with conventional manual repairs.

The method will be applied to aircraft fuselage and wing structures as well as helicopter rotor blades.

Under the current project, which ends in April, the system has been designed as stationary equipment, which can be employed at a maintenance base. However, a follow-on project is to begin immediately afterwards to develop a mobile system by 2015, which can be deployed to undertake repairs in aircraft-on-ground (AOG) situations.

The system has been developed with reasearch funding from Germany's federal ministry of economic affairs.