Out of autoclave bonded repair process and implementation for aircraft composite structures

Abstract

With the entry into service of aircrafts with a very high percentage of composite materials the necessity of efficient repairs for such structures arises. Airbus has developed an out of autoclave bonded repair process for highly loaded composite primary structures of the A350XWB. It can be used at production plants but also in the in-service operation of the aircraft. Bonded repairs eliminate the requirement of rivets in carbon fibre parts allowing flush repairs that complies with the original component functionality and requirements. The repair process includes removing the damaged plies by successive milling steps, each one equal to a single ply thickness. The repair technique consists on the application of a soft patch with specific repair materials, different from those involved in the manufacturing process and with the unique characteristic of curing at low temperature in out of autoclave conditions. The aforesaid facilitates application in plenty of circumstances and scenarios. This paper describes the coordinated investigation performed in order to provide a robust and sound out of autoclave repair system and process. The combination of feasibility trials in actual repair conditions and material characterization tests proved to be essential to understand the critical steps and to optimize the process performance.