787 delamination

I saw on the news that the carbon Boeing 787 is experiencing skin delaminations. Anybody know what kind of glue/epoxy they are using? The sections in question are towards the tail , made in the South Carolina plant.

 

In 90 % 0f failures it not the material but human failure and bad or poor workmanship !!

 

Very reassuring, if you aren't travelling on the other 10%. I advise taking a tube of Tarzan's Grip on the flight, just in case.

 

The old Comet aircraft did the same thing when the skin peeled off !! A long time back and the plane crashed !!can check that out on you tube i think thats where i was it long time back .It was completely new technology then using adhesives to glue metal skins to metal frames . it be more worried the pilot was sobber than worrying about the plane falling apart .

 

the comet had fatigue cracks that started around the windows and spread, the program i watched said the skin was to thin and could not handle the pressure cycles. mr e super glue would be better, you only have to hold the wing for 60 seconds while the glue dries.

 

You got it !! was a long time ago and details were a little hazy but was the first time adhesives were used !!:idea:

 

tunnels, i watched a program about the comet on discovery not long ago, it was a shame they had those dramas because the pilots that flew them loved them and britain was leading the jet age.

 

And this dramatic accident of a 737 Aloha Airlines Flight 243 attributed to epoxy debonding

Quote from Wikipedia"Investigation by the United States National Transportation Safety Board (NTSB) concluded that the accident was caused by metal fatigue exacerbated by crevice corrosion (the plane operated in a coastal environment, with exposure to salt and humidity).[5][6] The root cause of the problem was failure of an epoxy adhesive used to bond the aluminum sheets of the fuselage together when the B737 was manufactured. Water was able to enter the gap where the epoxy failed to bond the two surfaces together properly, and started the corrosion process"

Dino

 

that plane was also had thousands of pressure cycles due to the short routes it flew. excellent vision for scenic flights in that configuration though.

 

An older friend of mine was a aircraft engineer was close to the place where all this was being built and was there when it happened . i remember him talking about it and was excited recalling all the innovation and new ideas that went into that plane . now they are taken for granted as technology has improved and materials have got better .

 

The original Comet design made a fundamental engineering error and had square corner windows, which lead to stress risers in the skin, which eventually lead to catastrophic failures. After a few crashes, the absence of a NTSA organization to look into the situation, it was finally found (after some really exhaustive testing) the windows needed rounded corners to eliminate the stress riser potential, thus saving the skin. A simple oversight, done for styling purposes, fixed and the jet went on for finally removed from service 10 years ago after a 50 year run. Cabin pressurization exasperated the stress riser issue, but it also had other design problems to work out as the first commercial jet. Nothing to do with epoxy here folks.

The difficulties of Aloha Airlines Flight 243 were maintenance related and any adhesive would have failed given the same set of conditions. The air frame received nearly 20% more pressurization cyclic events over it's recommended service and coupled with the maintenance program in place at the time, permitted stress fractures to mitigate into a catastrophic failure.

The Dreamliner has a number of issues, which in itself isn't much of a surprise, as all new products of this type will experience levels of "discovery" during testing, assembly, etc. This list of things wrong is extensive, but the wing stringer cantilever problem is a point loading issue and is receiving a redesigned stringer termination and wing box root (titanium to the rescue). The delamination problems experienced by Air France is probably a vendor issue, but again a stress riser/point loading situation where the stabilizer section ties to the fuselage. Once again it appears that stingers, near an opening and point loading, causing stress risers at this joint. More laminate in this area will likely be the solution. So, again not an epoxy failure, though epoxy is being used, it's an engineering issue, not a material choice problem.

Considering the innovation and complexity of these "devices" and the most conservative nature, of the FAA and related regulatory agencies, these issues will be sorted and addressed. No epoxy issues here, just more lack of sleep for the geeks, as they work through the inevitable bugs.

 

Interesting information. I should have put this in the composite construction section. The delamination did suggest incomplete wetting out or a cure not complete in the autoclave or a resin-catalyst mix issue. In any case those would not have been the epoxy itself but the construction process. I am curious about the epoxy formulation as they have to be manufacturing it in large quantities and anything rated for aircraft should be suitable for boats. Does anyone know if they are using infusion or are they prepreg layups?

 

I flew on something about 4 years ago, Airbus, Boeing, I don't know, but it was laminated, no rivets etc. The wing looked fine on the ground, as we ascended a bump formed and got bigger and bigger. It eventually got to the size of a large dinner plate and as we descended it disappeared so everything looked normal back on the ground. I drew a picture of where it was and told the pilot about it but got a brush off non answer. I gave the drawing to the flight attendant and told her to look next time they were up.

 

The Aloha 243 accident was primarilly (root cause) an epoxy debonding issue which gave rise to a chain of processes that further weakened the structure near the front door area. The epoxy itself was probably not at fault. The preparation of the aluminum surface and cyclical stress was.

Once water vapor (spiked with salt) started to degrade the bond line loss of adhesion progressed slowly along that line further concentrating the stress.

A rigorous process of aluminum surface preparation (generically referred to as phosphoric acid etch) is necessary to achieve long term aluminum-epoxy bonding especially in the marine environment.

Dino

 

How can the "root cause" be an "epoxy debonding issue", yet "not at fault"?

This incident like most, was a cumulative set of events, that resulted in a bond failure, as well as other failures, all within a few moments of each other. Again it had nothing to do with the epoxy bond, but was a maintenance issue.