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Qatar Airways grounds 13 Airbus A350s as fuselage degrading

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Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#11
"How safe are modern aircraft with carbon fiber composite fuselages in a survivable crash?" https://www.materialstoday.com/carbon-fiber/features/how-saf...

PDF direct link: https://www.materialstoday.com/download/127653/

In Space, but relevant:

"Thermomechanical Fatigue of Unidirectional Carbon Fiber/Epoxy Composite in Space"

https://www.hindawi.com/journals/je/2020/9702957/

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#12

Given that the Qatari regulator ordered the grounding and that Qatar Airways is state owned that seems like a pretty big conflict of interest. Especially with Qatar Airways refusing delivery of any more a350s until the problem is fixed (in a time of extremely low levels of international air travel).

Qatar is bringing A330s out of storage and up-gauging some routes to 77Ws, which have significantly higher fuel-burn (due to more seats, and a older airframe). I doubt this is just a negotiating position.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#13
post #11

"How safe are modern aircraft with carbon fiber composite fuselages in a survivable crash?" https://www.materialstoday.com/carbon-fiber/features/how-saf... PDF direct link: https://www.materialstoday.com/download/127653/ In Space, but relevant: "Thermomechanical Fatigue of Unidirectional Carbon Fiber/Epoxy Composite in Space" https://www.hindawi.com/journals/je/2020/9702957/

The 320s have had composite parts forever. So have virtually every plane since then, The 787, for all it's other faults, hasn't had this issue, and uses a more radical design for it's 787, versus the A350 which still uses stringers and panels, rather then put more load on the CFRP.

But that said, given that Lufthansa is also apparently pulling and repainting it's A350s, there may be some reaction here.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#14
post #8

I've been a long time carbon-fiber skeptic. Only an armchair materials enthusiast but carbon fiber construction seems to lack the margin for fatigue that aluminum has. It seems to me that when carbon fails it fails catastrophically, while aluminum allows some "give". Now it seems carbon fiber doesn't have the longevity either? I am aware the aluminum can "work harden" over time and become more brittle as well. No mat…

Keep in mind we have 30-year old A320s flying around using carbon-fiber, so we would seem to be out of the trial-period phase. This issue appears to be a cosmetic one with regards to the paint layers, not structural (see my other comment).

Apparently A350 are built with Teijin Tenax thermoplastic carbon. Brochures say it cures in one minute, eliminating autoclave. Could be different from normal resin based carbons.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#16
post #14
post #8

Earlier quoted context omitted.

Keep in mind we have 30-year old A320s flying around using carbon-fiber, so we would seem to be out of the trial-period phase. This issue appears to be a cosmetic one with regards to the paint layers, not structural (see my other comment).

Apparently A350 are built with Teijin Tenax thermoplastic carbon. Brochures say it cures in one minute, eliminating autoclave. Could be different from normal resin based carbons.

Yes, and quite possibly they did not factor in the long term differences between interaction of paint and materials.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#17
post #11

"How safe are modern aircraft with carbon fiber composite fuselages in a survivable crash?" https://www.materialstoday.com/carbon-fiber/features/how-saf... PDF direct link: https://www.materialstoday.com/download/127653/ In Space, but relevant: "Thermomechanical Fatigue of Unidirectional Carbon Fiber/Epoxy Composite in Space" https://www.hindawi.com/journals/je/2020/9702957/

This has no bearing on this article, it is not about fatigue but about surface defects, not structural defects.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#18
post #5

This was first reported back in January when a Qatar Airways Airbus A350 was in Shannon for a repaint. When the paint was stripped they found surface coating irregularities. This is apparently cosmetic and not structural. This was one of the first A350s to be repainted. Qatar has 53 Airbus A350 aircraft, so why these particular 13 is the question now.

Are they in a particular sequence or randomly distributed across the 53 hull numbers? If the former it might be a process change somewhere in the paint or resin/polymer formulation.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#19

I've been a long time carbon-fiber skeptic. Only an armchair materials enthusiast but carbon fiber construction seems to lack the margin for fatigue that aluminum has. It seems to me that when carbon fails it fails catastrophically, while aluminum allows some "give". Now it seems carbon fiber doesn't have the longevity either? I am aware the aluminum can "work harden" over time and become more brittle as well. No mat…

Yeah I worked in NDT for a bit and it's very difficult to test carbon fibre for damage or delamination under the surface. There are techniques but not as good as for aluminium. And as you said they don't have a nice plastic region like metals.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#20
post #5

This was first reported back in January when a Qatar Airways Airbus A350 was in Shannon for a repaint. When the paint was stripped they found surface coating irregularities. This is apparently cosmetic and not structural. This was one of the first A350s to be repainted. Qatar has 53 Airbus A350 aircraft, so why these particular 13 is the question now.

The rumor is that some combination of paint, stripper and CFRP led to the actual mesh being exposed. If so, that goes considerably further then cosmetic.
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