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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

#21

Post by belter »

jacquesm wrote: post #17
belter wrote: 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.

See comment above from InTheArena.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#22

Post by Scene_Cast2 »

JKCalhoun wrote: post #6

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…

If anyone is curious about material science, some keywords are "stress strain curve", "plastic vs elastic deformation", and "fatigue limit" (that last one is really cool).

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#23

Post by himinlomax »

JKCalhoun wrote: post #6

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…

Carbon fiber and other composites are actually much better wrt fatigue than aluminium. In fact they are pretty much immune to it, if you mean the word in the sense it's used in metallurgy. They are however much worse for impact resistance.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#24

Post by orra »

IshKebab wrote: post #19
JKCalhoun wrote: post #6

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.

> [carbon fibre] don't have a nice plastic region like metals.

An amusing turn of phrase, given we are presumably talking about carbon fibre reinforced plastics.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#25

Post by akiselev »

baybal2 wrote: post #3
naturalauction wrote: post #2

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).

Well, a good time to say Bravo to their regulator then. Imagine if the regulator, and the state airline was ran by people half of whom shared the same surname, and it happened, say, in USA.

Qatar has a population of over 2.5 million but only about 300,000 of those are native Qataris. Even if they have different last names, chances are they're somehow related.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#26

Post by belter »

jacquesm wrote: post #17
belter wrote: 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.

The mention of cracks was coming from this post:

"A QR A350, A7-ALL MSN 036, a 4 year A350, was being prepped for paint removal from the standard QR livery and repaint into the Qatari World Cup 2022 livery at SNN when IAC engineering discovered that the airframe had premature cracks in the composite fuselage..."

https://www.airliners.net/forum/viewtopic.php?f=3&t=1456315&...

I am aware of Airbus statement that is only surface related. It is surprising they took the airplane back to Toulouse. So its certainly something more than just a paint issue.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#27

Post by walrus01 »

EMM_386 wrote: post #8
JKCalhoun wrote: post #6

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).

there are also a number of enthusiastic road cyclists riding 20, 25 year old carbon fiber frames - if not crashed or mechanically damaged (in a way that would also total beyond repair a thin walled aluminum frame like a cannondale CAAD8), they last quite a while.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#28

Post by bdjddd77 »

akiselev wrote: post #25
baybal2 wrote: post #3

Earlier quoted context omitted.

Well, a good time to say Bravo to their regulator then. Imagine if the regulator, and the state airline was ran by people half of whom shared the same surname, and it happened, say, in USA.

Qatar has a population of over 2.5 million but only about 300,000 of those are native Qataris. Even if they have different last names, chances are they're somehow related.

This is true, briefly thought I was in manila when doing a hotel stop over, only the hotel manager seems to be a native. Horrible country, but I'll do the gov subsided stopover frequently when travelling back and forth.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#29

Post by jacquesm »

belter wrote: post #26
jacquesm wrote: post #17

Earlier quoted context omitted.

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

The mention of cracks was coming from this post: "A QR A350, A7-ALL MSN 036, a 4 year A350, was being prepped for paint removal from the standard QR livery and repaint into the Qatari World Cup 2022 livery at SNN when IAC engineering discovered that the airframe had premature cracks in the composite fuselage..." https://www.airliners.net/forum/viewtopic.php?f=3&t=1456315&... I am aware of Airbus statement that is onl…

Interesting. I'm curious what the eventual outcome of this will be but it is always very hard to keep track of such stories further down the line, especially if the result is non-spectacular.

Re: Qatar Airways grounds 13 Airbus A350s as fuselage degrading

#30

Post by AceyMan »

jacquesm wrote: post #17
belter wrote: 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.

On the assumption these panels are a component of the pressure vessel—and it would seem that they are—then they very much are structural components. Not in "the wing will fall off" kind of way but in "the whole cabin will explosively decompress" way.

/Acey

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