I'm not trying to bash the 787 or Boeing, but thinking about the pervasive use of carbon fiber in it, I can't help but think of the MX difficulties that might result. More specifically I wonder how Boeing has addressed these issues. In addition to the fuel tank issue I brought up in another thread I wonder how the repainting of the 787 will be accomplished.

Working in the paint hangar at Delta for 2 years I know first hand the difficulties of repainting composites. Current composite panel construction and chemical paint stripping techniques don't mix. Currently all composites have to sanded with a DA(dual action) sander. This is a time consuming process. A 4X8 foot panel can take one person 8 hours to sand. Extreme care must be taken as it is very easy to remove too much material and before you know it you're into the structural plies of the panel. A time consuming repair is now required. Suffice it to say that a lot more labor will be required to repaint one of these babies and it will have to be very skilled. That is unless Boeing has or will develop new more economical refinishing methods.

Another problem I see is that paint can be considered an integral part of the composite. On metal, cracked paint just peels off, doing no damage to the metal. Cracks in paint on composites on the other hand propagate down into the resin matrix. There are different non structural protective plies applied to the top surface of the panel to resist this and in many cases a high build primer can be used to repair this. I have, however, seen 757 fan cowls that have been scrapped due to this phenomenon. They looked like somebody painted them in a faux crackle finish. I'm sure faulty refinishing is probably to blame but that just reinforces my point about the high skill level and extended time that will be required to refinish the 787. A cost factor that airlines might want to consider in their purchase analysis.

Dl757Md

Given that composites won't corrode wouldn't the 787 need to be repainted less often?

I get the feeling that Boeing knows what they are doing. They have already fabricated and painted test examples of the 787 fuselage.... givem them credit guys, it's their job to build airplanes. I think applying paint and repairing a dent has crossed their minds  

DfwRevolution

I think applying paint and repairing a dent has crossed their minds

I never questioned whether Boeing has thought about it, I asked what have they done about it.

More specifically I wonder how Boeing has addressed these issues.

Having a background in aircraft refinishing as well as overhaul, naturally I'm interested in what they have come up with to solve known issues with composites that to my knowledge haven't previously been addressed adequately. Expanding on my example of a fan cowl. It's one thing to trash a carbon fiber fan cowl because it's uneconomical to repair and quite another to trash an entire airplane. I'm sure if you would have asked Boeing when they designed the 757 they would have told you the fan cowls will last the lifetime of the airframe. I'm here to tell you that at least sometimes they don't. The only reason being is that they are made of carbon fiber. No service damage just exposure to vibration, fluids, and the elements. Now I completely agree that Boeing or anyone else for that matter wouldn't use carbon fiber for a whole airplane if they didn't have a lot of data to back it up. That's not the point I'm trying to make. Being a mechanic I just wonder how we'll fix it.

SATL382G
Given that composites won't corrode wouldn't the 787 need to be repainted less often?

Aluminum structures have the option of being painted due to the fact that Al forms a surface oxidation layer that protects the metal underneath. This is born out by the liveries of AA and others who use bare metal. Composites on the other hand MUST be painted to protect them from moisture and UV light both of which are very detrimental to composites.

Dl757Md

I never questioned whether Boeing has thought about it, I asked what have they done about it.

It isn't at all out of line to contact Boeing in these matters. Mention you're a humble avation enthusiast and ask a reasonable question and they will get back to you in a week or so. They would probably be happy to answer this question.

[email protected]

Sorry if I jumped the gun a bit, but there have been a million "What will Boeing do when "X, Y, or Z" happens to the 787" threads.

Ask Boeing! What and miss all the fun lively debate we have on this forum!
Never!!!
Seriously though, thanks for the good advice Dfw.  

Dl757MD

I think I can understand what DI757 is trying to get too.Although I also believe Boeing may have thought about this too in detail.
How effective will paint stay on a Composite Structure as compared to Al surface.
Is the Binding better on Composite.
regds
MEL

I've just read a story in Aviation Week & Space Technology, which had a article on the 787 which discussed the carbon fiber issues. I'm afraid I can't find the magazine at the moment.

They discussed that Boeing built section 48 due to it's shape as it was the most difficult and therefore they would learn the most from. They also mentioned painting which explained that the die the carbon fiber layers are laid in is milled with a rough pattern which would be left on the surface of the aircraft structure after curing. The test piece they built had 4 different levels of roughness to see what was best, as it had to be enough for the paint to stick to but not too much as to cause drag.

Rgds CCA

[Edited 2005-02-15 10:44:10]

Years ago I remember reading that Boeing and 3M were looking at using thin polymer films, also known as appliques, instead of paint. The idea was that instead of painting they would apply these appliques. This would mean not having to paints and solvents. How hard it would be to remove I don't know. Here's a link with some more information. Whatever happened with this idea I don't know. Guess I'll have to do a bit more research.

http://www.boeing.com/news/releases/1997/news.release.970422.html

Another possibility would be to use more different layers of paint. One layer could be a "stop layer" would be layer which (better) resists sanding, chemical stripping or whatever you are using to remove the paint. It's just speculation, but why not?

Another point is that Boeing claims D-check intervals of 12 years, so repainting won't be needed very often. In case of an operator change, maybe simply another paint layer may be applied without stripping?

Finally, I have never heard that the repainting of Airbus composite parts (e.g. vertical stab) is a big problem.

The paint issue is maybe a backdraw of composites, but in the overall calculation composites are still the best material for airliners.

Greetings from Berlin

A350

P.S.: sorry for all that speculation in this post