The new process, which results from more than two years of collaboration between the two companies, uses lasers to remove sections of damaged material, while leaving intact the remaining healthy fibers and resin. The technique does not apply force or vibration to the structure, so it does not affect the structure's overall strength or integrity. After the laser treatment, the area where damaged material has been removed is left clean and ready for repair. This is done with a replacement patch, which is cured in place using a localized heating mat.
SCLR Lasertechnik specializes in using lasers to selectively remove coatings. The company performs surface preparation of machined parts for painting or gluing, as well as surface activation of carbon fiber-reinforced plastic and glass fiber-reinforced plastic composites, and removing paint in both types of composites. (Watch videos showing SCLR's surface preparation and paint removal of composite parts here.)
In the statement, John Cornforth, head of technology at GKN Aerospace, says:
With the first installation of this prototype equipment we are now commencing work on extending the ability of this new process to handle various shapes and sizes of structure. We believe this process has enormous potential; composite materials increasingly dominate the airframe, meaning their reliable, effective repair is critical for operators and the industry, alike. This technology will allow the efficient, cost-effective and high-quality preparation of almost any composite assembly for repair.
Rob, keeping planes in service longer is certainly one of the benefits hoped for from this new technology. The primary benefits, though, are getting them back into service faster, lower cost, more consistent repairs, and techniques that don't shorten a plane's service life by damaging composites during repair (the lack of force or vibration applied to the structure).
Wow! Thanks for this, Ann. It's often the obvious solutions that are the most frustrating. The use of dirty, violent abrasive cutting techniques on composites is such an obvious no-no when it comes to disturbing the fiber alignment and potential of layer separation in non-damaged portions of the material. I'm guessing previous attempts to cut fiber/resin composites with a high-power laser resulted in either a puddle of goo or a fire. Kudos to Lasertechnik for developing an appropriate combination of laser power, frequency, modulation, and beam profile for use with composites. This will have wide applications.
William, I assume that this technology relies on very precise control of the laser to work. There must be some new advances in laser focus or control to make it possible. It is, becuase of the results you mention, not an obvious choice, but someone has figured out how to make it work (werk?).
Composite repairs cannot be fully checked for quality via visual inspection like conventional repairs. I often wondered how they plan to handle this problem. And well, of course, let a robot do it - they are consistant and have no bad days.
I find it amazing what SLCR Lasertechnik can do with regard to coating removal. They claim, for example, that they can strip the paint from a part while leaving the primer intact. They can also remove paint from selected areas without the need for masking. I can think of a lot of occasions in which the ability to do these things would have been very useful.
By the way, it appears that the company is called SLCR (Selective Laser Coating Removal), not SCLR. The name was misspelled in GKN's press release.
Chuck, Boeing doesn't seem to like to discuss this subject in any detail, so their specific plans are unknown. Since GKN Aerospace is a major supplier to Boeing, one can always make reasonable guesses. That said, Boeing was having a lot of trouble earlier this year with apparent delam issues of the 787's composite fuselage: http://www.latimes.com/business/la-fi-0223-dreamliner-problem-20120223,0,6402954.story
Hey William, glad you liked this story. It does seem kind of 20/20 in hindsight, especially the "don't bang on that complex composite layer" part. The other part that also seems obvious is the crossover from removing coatings on composites via laser--which SCLR Lasertechnik already does, and which sounds like a delicate process--to using lasers to repair composites with what sounds like a very similar method. Maybe someone from SCLR Lasertechnik was having a beer with someone from GKN Aerospace, and one of them said "I wonder what would happen if you used this for that...?" Just a guess.
The art and science of composite repair is constantly evolving. The advent of the B-787 class of aircraft is a game changer. In the past, composite parts have been considered "secondary structures", such as flight control surfaces, landing gear doors, floor panels, etc. Repair procedures were fairly well understood and integrated into the maintenance programs as normal operations. Now, with the composites forming a major portion of the load-bearing structure, the industry has to really step up their game. Our company is one of a few supplying composite repair systems for this purpose. We see every day the struggles the OEMs and the repair activities are having with these issues.
There are really four phases or issues of consideration when repairing composites. 1. Identification of the damage. 2. Preparing the area for repair (removing damaged material). 3. The actual repair (replacement of damaged material) 4. Verification of the process (QA /QC, NDT).
The subject of this article partially addresses #2. A few of the posters flagged some of the issues involved. How practical is the robot for use in-situ scenarios? How well can it negotiate compound curves, fasteners, varying material densities, and unknown sub-strucrures? One poster alluded to "dirty, violent abrasive cutting techniques on composites". Removal of damaged material is actually more surgical, with the use of hand-held routers, die grinders, and the like with diamond and carbide bits designed for this purpose. There is a large human expertise factor required for all phases of composite repair. The application of robotic technology to as many of these processes as possible is laudable, but more development is required. There is as much art as science involved with complex repairs.
Since most composite repairs require the application of heat to cure the aerospace materials, the real challenge is ensuring that heat is uniformly applied and reaches all parts of the material under consideration. This is especially challenging when dealing with carbon-fiber structures. Carbon conducts heat relatively well. The heat wants go everywhere, not just where it is needed. We are actively working with the OEMs to develop equipment and technology to ensure this is possible.
All phases of composite repair have come under much closer scrutiny from the FAA recently. They see the potential for a catastrophic event due to an improperly performed repair. It's back to basics: Training, proper procedures, process control, verification. Welcome to the friendly (safe) skies!
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