Signed during a ceremony at the recent JEC Composites Show (March 24-26, Paris, France), a collaborative agreement between GKN Aerospace (Isle of Wight, U.K.) and SLCR Lasertechnik (Düren, Germany) has initiated joint investigation of the use of automated lasers in composite aircraft structure repair. Intended to replace the manual grinding currently required to prepare damaged surfaces for bonding, the laser technique reportedly will apply no force or vibration to the structure and, therefore, will have no detrimental impact on the composite component’s strength or integrity.

The process uses a CO2 laser generator the size of a small, three-drawer filing cabinet, with a camera mounted on the top. It is linked to a receiver camera mounted on a small robot of the appropriate size for each task. The robot contains a laser “gun” with the laser optics, in a package small enough to permit accurate movement over the part surface, says Phil Grainger, senior technical director and chief technologist at GKN Aerospace. The laser evaporates the organic resin one ply at a time, leaving the damaged fiber behind, until good structure is reached. Grainger notes that part of the development effort will involve refining the process for clearing away the fibers left behind. Damaged areas prepped with the laser can be repaired using conventional methods, achieving comparable strength in one-third of the time required for hand grinding, with a potential 60 percent cost reduction. The technique is reportedly useful in the workshop or while the part is still mounted on the aircraft and can be applied to both monolithic laminates and honeycomb structures.

“As composite materials increasingly dominate the airframe,” says Grainger, “their effective and swift repair becomes ever more critical. This new agreement with SLCR aims to deliver first-generation equipment in just two years.”

The program is funded by the U.K. government as part of the Environmental Lightweight Fan (ELF) Research Program, a GKN/Rolls-Royce effort aimed at developing composite fan blades.