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Boeing's 787 Dreamliner uses composites for various airframe components.  (Source: Boeing)

UV Light Shows Resin Bleeding into Fracture  (Source: Gizmag)
Future composite aircraft could have a circulatory system filled with the resin

Miniscule cracks and flaws in the airframe of commercial and private aircraft can lead to catastrophic failure of the aircraft leading to loss of life and property. Commercial airlines routinely inspect their aircraft for damage and issues that could lead to an accident. The problem is that small cracks and light damage can be difficult to detect and impossible to see with the naked eye.

Aerospace engineers from Bristol University have developed a new method to complement routine visual inspections of commercial aircraft made from composite materials such as the Boeing 787 Dreamliner.

The researchers have devised a way to fill the hollow parts of composite aircraft with a self hardening resin. When the airframe is damaged the resin would bleed out of the hollow spaces into the crack and seal the damaged area with enough strength to maintain flight and safely land. The engineers also say that future aircraft could have the resin moving continuously through a circulatory system built-in to the airframe.

The resin doesn’t return the airframe to 100% of its strength, but the researchers say that the resin would allow the damaged area to regain 80% to 90% of its former strength. The process used by the engineers is likened to the process the human body uses to heal after a cut. In the body, blood leaks into the damage tissue where platelets form clots to stop bleeding and a scab forms to aid in healing and protect the area. In the engineers system the resin is the blood and the hardened resin is like a clot and scab protecting the area.

The resin the engineers propose to use would have a blue color allowing ground crews to readily identify areas where the resin has affected repairs to small areas of damage. Project leader Dr. Ian Bond said, “This approach can deal with small-scale damage that’s not obvious to the naked eye but which might lead to serious failures in structural integrity if it escapes attention. It’s intended to complement rather than replace conventional inspection and maintenance routines, which can readily pick up larger-scale damage, caused by a bird strike, for example.”



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Sounds great, but...
By MrBlastman on 5/30/2008 1:20:49 PM , Rating: 2
How much weight will the resin flowing through the surfaces add to the plane?

I think this is a wonderful idea and could be a great solution to the fear over composite aircraft. I am worried about weight though as it could take up quite a bit of either room or mass. Who knows?

Does anyone know how often the FAA requires a standard airframe inspected? With this solution I'd think the airframe would need to be inspected more frequently to keep up with the problems as they occur.

I don't see composites (such as carbon fiber) being used on areas like the leading edges, but I imagine they could be used on the rest of say the wing surface and perhaps fuselage.




RE: Sounds great, but...
By MozeeToby on 5/30/2008 1:48:52 PM , Rating: 4
The 787 already is a composite airplane, about 50% of the total airplane is made of composite parts including nearly all of the fuselage.

Using composite provides several benifits; less fatigue damage over time (allowing higher pressures in the cabin), no corrosion (allowing higher humidity in the cabin), and much reduced weight.

I can't imagine the liquid resin weighing in at more than aluminum so it will probably still produce a lighter aircraft than traditional materials. Of course, it would be heavier than a composite design without the resin (unless, of course, they can trim the fat off the composite design since the resin gives them a safety net when damage occures).

The 787 is an ambitious project for many reasons; taking advantage of both new technologies and new globalization strategies. Unfortunately, being years ahead of its time has taken its toll and the project is well behind schedule.


RE: Sounds great, but...
By SoCalBoomer on 5/30/08, Rating: -1
RE: Sounds great, but...
By chmilz on 5/30/2008 1:49:49 PM , Rating: 3
I would be concerned about a product like this creating a mindset where repair technicians would rely on the resin to make the repairs, and cause oversights and a general disregard for hairline faults that could cause a failure resulting in injury or death.

I enjoy the idea of it as an in-flight savior, but not as a whole self-repair system with it's own infrastructure.


RE: Sounds great, but...
By KristopherKubicki (blog) on 5/30/2008 1:54:42 PM , Rating: 3
I think it wouldn't be hard to detect a drop in pressure of the resin if they had it in some kind of pump system. Then if there was a rupture, land the plane and do a full inspection immediately


RE: Sounds great, but...
By Smartless on 5/30/2008 2:11:24 PM , Rating: 2
You know... you gotta wonder what they mean "hollows". Are there gaps inside of the composite lattice structure that allow this or would it be more like a sandwich with resin in the middle?


RE: Sounds great, but...
By stryfe on 5/30/2008 2:30:29 PM , Rating: 4
That sounds delicious!


RE: Sounds great, but...
By MrBlastman on 5/30/2008 2:37:21 PM , Rating: 2
Mmmm... Resin sammich!

I bet it really 'sticks to your ribs'

har


RE: Sounds great, but...
By stryfe on 5/30/2008 4:56:11 PM , Rating: 3
Don't forget the composite lettuce structure! ;)


RE: Sounds great, but...
By Keeir on 5/30/2008 3:31:51 PM , Rating: 2
Composite structure is typically a sandwich of high strength layers of graphite fiber "tape" with a middle of a shear carrying layers of honeycomb type foam.

The idea (I think) is to fill the honeycomb with resin. This would significantly increase the wieght of the aircraft and the system to "pump" it or monitor it would only not really save much wieght.

My main concern is that this may repair sections to 80-90% strength, but the actual repair would be invisible to all but fairly sophisticated inspection methods. Therefore, no permanent repair (100%) would be made and potentially this could cause problems since engineers may have originally counted on the structure being at either 100% or 0% (visiblely damaged).


RE: Sounds great, but...
By Solandri on 5/30/2008 5:35:36 PM , Rating: 2
The whole point of using honeycomb is to provide stiffness without weight. If you're filling the honeycomb with material, it defeats the purpose of using honeycomb in the first place.

We covered self-repairing composites when I took courses in it 12 years ago. At the time it was theoretical so I don't know if this stuff works like the theory back then. But the theory goes: Composites are just strong fibers (glass or carbon) held together by a resin matrix. The fibers provide the strength, the resin transfers load between fibers. When it fails, the fibers detach from the the resin, like nails pulling out of wood.

You can repair it by infusing the damaged area with new resin. Most resins (like epoxy) come in two liquid components which solidify when mixed. The theory for self-repairing composites was to imbed bubbles of these two liquids within the resin. When you get a significant fracture, some of these bubbles are burst. The liquids seep out, mix, fill any holes, and solidify, thus re-bonding the fibers to the matrix.


RE: Sounds great, but...
By GTVic on 5/31/2008 12:57:28 PM , Rating: 2
If you fill the entire honeycomb with resin then you defeat the purpose of the honeycomb. So that does not sound correct.

But if the material would have to crack all the way through to the resin before the resin would react then at that point wouldn't you have damage too severe to be repaired?


RE: Sounds great, but...
By jRaskell on 6/2/2008 12:08:20 PM , Rating: 2
quote:
but the actual repair would be invisible to all but fairly sophisticated inspection methods.


From the article:

The resin the engineers propose to use would have a blue color allowing ground crews to readily identify areas where the resin has affected repairs to small areas of damage


RE: Sounds great, but...
By Solandri on 5/30/2008 3:14:00 PM , Rating: 2
quote:
I would be concerned about a product like this creating a mindset where repair technicians would rely on the resin to make the repairs, and cause oversights and a general disregard for hairline faults that could cause a failure resulting in injury or death.
The whole rationale for this is that composite failures are very difficult to detect. You don't get a hairline crack. You get multiple short cracks which zig-zag between carbon fibers (you can kinda see it in the picture). Taken separately, each short crack is relatively normal in a composite. But combine them in a small space and they can turn deadly

In other words, the danger of repair techs failing to ever notice the damaged part far exceeds the danger of repair techs deciding to play minesweeper instead of fixing damaged parts.


RE: Sounds great, but...
By V3ctorPT on 5/30/2008 3:17:31 PM , Rating: 2
yeah, yeah... it's nice... but when can I buy it to put on my girlfriend's bumper?


RE: Sounds great, but...
By MrBlastman on 5/30/2008 3:46:00 PM , Rating: 1
Her bumper is damaged or you broke her trunk? Which is it? ;)

Sounds like a personal problem to me.


RE: Sounds great, but...
By V3ctorPT on 5/30/2008 4:53:32 PM , Rating: 1
lololol....


RE: Sounds great, but...
By Reclaimer77 on 5/30/2008 5:11:27 PM , Rating: 2
quote:
I am worried about weight though as it could take up quite a bit of either room or mass. Who knows?


Well I'm pretty sure the engineers who have FORGOTTEN more about advanced polymers and materials then you or I will ever know have already considered that.


RE: Sounds great, but...
By aeroengineer1 on 6/1/2008 4:01:38 AM , Rating: 2
As I understand the process, it is basically micro capsules that are in the resin. These capsules would probably contain a resin that is two part. These capsules, because they are embedded in the resin and hence subject to the same forces that the joint would see, or at least the same order of magnitude, would fracture because of the local stresses.

As for the poster that disputed the high recovery of strength, it may be a little high, but because composite materials do not fracture like metals, but in layers, there is a good chance that this could provide a very high strength repair.

To the poster that wanted to know about airframe inspections; there are many different levels of inspections that a commercial airframe goes through. Some inspections are just things like checking the oil. Other inspections such as a D check basically strips the airplane of all of its interior and pretty much everything else. The airframe is thoroughly inspected.


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