bucky707
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787 Repairs

Mon Sep 18, 2006 2:40 am

Funny source, but I was reading an article in a golf magazine talking about the impact the 787 will have on the availability of carbon fiber for golf club shafts. The article went on to talk about the manufacturing process of the 787 fuselage compared to manufacturing a golf shaft.

Anyway, long build up but here is my question. When a 787 fuselage inevitably gets damaged (a catering truck running into it for example) what will the process be to repair it? Could there be damage enough to compromise the whole structure?
 
EMBQA
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RE: 787 Repairs

Mon Sep 18, 2006 2:50 am

Composites are very easy to repair and are made up of a series of layers. The mechanic will remove ever growing areas of these layers. Most SRM's have the formula of size and edge distance. Once the area is ready layers of 'Impregnated carbon Fiber' are layed in. Carbon fiber, like wood has grains that must be layed in in a chris-cross patteren. Then the repair is backed by a firm surface, placed under a vaccum and heat is applied. Most bakes take 1-2 hours.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
Newark777
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RE: 787 Repairs

Mon Sep 18, 2006 2:50 am

Quoting Bucky707 (Thread starter):
Anyway, long build up but here is my question. When a 787 fuselage inevitably gets damaged (a catering truck running into it for example) what will the process be to repair it? Could there be damage enough to compromise the whole structure?

I'd assume there would be some sort of patch kit to cover the damaged area.

Harry
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kaneporta1
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RE: 787 Repairs

Mon Sep 18, 2006 3:25 am

Quoting Bucky707 (Thread starter):
Could there be damage enough to compromise the whole structure?

The answer is yes. One big disadvantage of CFRP is the NVD, Non Visible Damage, susceptibility. A truck may run crash onto an airplane without causing any external visible damage on the surface, but the impact may cause cracks or delamination inside the material. If this goes unnoticed for a while, it could mean trouble.
I'd rather die peacefully in my sleep, like my grandfather, not terrified and screaming, like his passengers
 
EMBQA
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RE: 787 Repairs

Mon Sep 18, 2006 3:30 am

Quoting Kaneporta1 (Reply 3):
If this goes unnoticed for a while, it could mean trouble

That is why you would do a disbond test...
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
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Stitch
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RE: 787 Repairs

Mon Sep 18, 2006 3:33 am

Quoting Bucky707 (Thread starter):
When a 787 fuselage inevitably gets damaged (a catering truck running into it for example) what will the process be to repair it?

Boeing has developed and continues to develop CFRP repair techniques to handle "ramp rash". However, one needs to remember that CFRP will be more resistant to "ramp rash" then current Al and Al-Li structures, since it is quite easy to significantly strengthen those areas with additional CFRP layers without adding significant additional weight. So impacts that might dent an Al or Al-Li panel would not dent a suitably reinforced CFRP "panel".

Quote:
Could there be damage enough to compromise the whole structure?

Yes, but such damage would be so great as to compromise an Al or Al-Li structure, as well. Remember, punching a hole into a CFRP structure no more catostrophically weakens it as a whole then it would if punching a hole in an Al or Al-Li structure. These planes are not "fragile" nor are they made of pane glass.  Smile

Quoting Kaneporta1 (Reply 3):
One big disadvantage of CFRP is the NVD, Non Visible Damage, susceptibility. A truck may run crash onto an airplane without causing any external visible damage on the surface, but the impact may cause cracks or delamination inside the material. If this goes unnoticed for a while, it could mean trouble.

This same issues applies to current Airbus products as it does current Boeing products with large composite structures like tailfins, elevators, and fueselage panels. It will also apply to future Airbus products like the A350XWB.

As such, Boeing and Airbus are developing procedures to detect these issues and the FAA and JAA are developing inspection procedures to ensure that such issues don't cause the hull loss of a 787 or an A350.
 
albird87
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RE: 787 Repairs

Mon Sep 18, 2006 3:44 am

Quoting Bucky707 (Thread starter):
I was reading an article in a golf magazine talking about the impact the 787 will have on the availability of carbon fiber for golf club shafts.

Yeah i can see that the old codgers in the golf clubs reading this article are goin to be shocked as there wont be enough carbon fibre in production for there new driver!! haha.

But seriously i remeber back int he 1980s when Rolls Royce tried to make carbon fibre blades for there RB211 engine but due to the frozen chicken testing (bird strike tests) and they found that the carbon fibre weakend when this happened in rain (or something along those lines with freezing) which made them go bust (but then the government took them back under there management).
Now my question is that will there be any problem with a composite with CF when used for the fueselage which might cause weakening in the material or had boeing solved this
 
dl757md
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RE: 787 Repairs

Mon Sep 18, 2006 3:58 am

Quoting Kaneporta1 (Reply 3):
The answer is yes. One big disadvantage of CFRP is the NVD, Non Visible Damage, susceptibility. A truck may run crash onto an airplane without causing any external visible damage on the surface, but the impact may cause cracks or delamination inside the material. If this goes unnoticed for a while, it could mean trouble



Quoting EMBQA (Reply 4):
That is why you would do a disbond test...

You would only do a disbond test if the contact with the A/C was reported. We all know that many ground equipment incidents go unreported. If no obvious damage is evident the offending person will many times think they didn't hurt anything and keep their mouth shut. It's not supposed to happen that way but human nature does get the better of our judgement from time to time. Now this hidden damage is unreported and remains hidden until the damage propagates to point of becoming visible or is found through a routine inspection.

Quoting Stitch (Reply 5):
This same issues applies to current Airbus products as it does current Boeing products with large composite structures like tailfins, elevators, and fuselage panels. It will also apply to future Airbus products like the A350XWB.

Current aircraft don't use composites in primary structure in the areas likely to receive ramp rash. The fuselage panels you mention are wing to body fairings which are secondary structure that only serve to smooth airflow. They don't have any affect on the structural integrity of the airframe. The tail and control surfaces are very unlikely to see accidental damage from ground equipment. If you ever look around the cargo doors and to a lesser extent the entry doors you will see many points where contact has been made and some sort of mtc. action has been taken. The point that Bucky is trying to make here, and I think it's a valid one, is that while yes carbon fiber has been used in aircraft before it has never been used in these damage prone areas that are critical to the structural integrity of the airframe. I'm sure Boeing is diligently working on ways to deal with these problems but I am also certain that service damage that happens once the plane has been in service for a while will bring up issues that weren't adequately addressed. They will then be addressed and we'll keep moving on. That's the way it works with airplanes. They are an ongoing engineering process throughout their entire lives. That is why we have service bulletins and ADs.

Dl757Md
757 Most beautiful airliner in the sky!
 
zvezda
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RE: 787 Repairs

Mon Sep 18, 2006 4:00 am

1. A catering truck impact is unlikely to damage a CFRP fuselage, which in the case of the B787 has many extra layers around the doors where a truck might hit it.

2. There are several different tests that can be used to detact cracks and delamination in the event of non visible damage. These tests would be required if the fuselage were to be hit by a catering truck.

3. Boeing have developed two different patch kits for the B787. There is a one hour patch procedure which is good until the next heavy maintenance visit. There is also a two hour patch procedure which is good for the life of the airframe.

4. Rain does not weaken CFRP.
 
keesje
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RE: 787 Repairs

Mon Sep 18, 2006 4:16 am

Quoting EMBQA (Reply 1):
Composites are very easy to repair and are made up of a series of layers. The mechanic will remove ever growing areas of these layers. Most SRM's have the formula of size and edge distance. Once the area is ready layers of 'Impregnated carbon Fiber' are layed in. Carbon fiber, like wood has grains that must be layed in in a chris-cross patteren. Then the repair is backed by a firm surface, placed under a vaccum and heat is applied. Most bakes take 1-2 hours.

No, composites are relatively hard to repair, no reason for denial. Extra layers don´t stop catering trucks and can even increase the chances of delamination. The FAA and JAA and airlines will have to be satisfied. Luckely Boeing isn´t underestimating.

In a labatory environment it isn´t easy. On smaller airports without good facilities and people it is different. Boeing is doing an extra effort by providing airframe guaratees in the new Goldcare maintenance program. They don´t do that for fun. They had to convince airlines. Also the specialized teams for doing major repairs on outstations will probably have to be expanded.
"Never mistake motion for action." Ernest Hemingway
 
sphealey
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RE: 787 Repairs

Mon Sep 18, 2006 4:17 am

===================

TITLE REVISITING COST EFFECTIVE FILAMENT WINDING TECHNOLOGY

ABSTRACT: [...] Recently announced results from NASA crash tests on the No. 1 Starship airplane, with a direct impregnation wet filament wound fuselage, have shown the prototype airframe to have phenomenal survivability to simulated crash conditions. [...]

http://www.sampe.com/store/paper.aspx?pid=337

===================

I believe it was Flying magazine that had a profile on the Starship a few years ago, and the one reported severe incident was a runway overrun incident in which everything in the way was badly damaged but the Starship fusalage was essentially not damaged. Admittedly the Starship is smaller in both diameter and length which would tend to make it stronger on a per kg basis.

As an aside, several people I know in aircraft manufacturing have told me that the 787 project is affecting the supply of carbon fibre worldwide.

sPh
 
kaneporta1
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RE: 787 Repairs

Mon Sep 18, 2006 4:22 am

Quoting Stitch (Reply 5):
This same issues applies to current Airbus products as it does current Boeing products with large composite structures like tailfins, elevators, and fueselage panels. It will also apply to future Airbus products like the A350XWB.

I never mentioned a manufacturer in my post. But my estimation is that the fuselage gets banged more than the wings, tailplane and fin.

Quoting Dl757md (Reply 7):
You would only do a disbond test if the contact with the A/C was reported. We all know that many ground equipment incidents go unreported.

You nailed it there. Also, even minor knocks can potentially cause NVD, so even if people think it's not worth inspecting because it's minor, it should be inspected.
I'd rather die peacefully in my sleep, like my grandfather, not terrified and screaming, like his passengers
 
redflyer
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RE: 787 Repairs

Mon Sep 18, 2006 4:32 am

Quoting Albird87 (Reply 6):
Yeah i can see that the old codgers in the golf clubs reading this article are goin to be shocked as there wont be enough carbon fibre in production for there new driver!!



Quoting Sphealey (Reply 10):
As an aside, several people I know in aircraft manufacturing have told me that the 787 project is affecting the supply of carbon fibre worldwide.

I know two people who are building Lancairs and both have run into shortages, which they say is directly attributable to Boeing sucking up market supplies.
My other home is in the sky inside my Piper Cherokee 180.
 
remcor
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RE: 787 Repairs

Mon Sep 18, 2006 4:41 am

Quoting EMBQA (Reply 1):
Composites are very easy to repair and are made up of a series of layers. The mechanic will remove ever growing areas of these layers.

Ok, but the original parts are cured in an autoclave (big pressure-cooker). The patch will not be cooked in an autoclave presumably... are the resins that are usued for the patches thus as strong as in the orginal parts? How would you get the air bubbles out of there? I'm sure they've got a way, but I'm wondering how.
 
Lemurs
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RE: 787 Repairs

Mon Sep 18, 2006 4:48 am

I remember seeing somewhere that in this first generation of CFRP fuselage, Boeing was intentionally overengineering to the point where any damage that could be dangerous will be visible, and small areas of hidden damage won't be a worry as a result...they'll have to spread to the point where simple inspection techniques will uncover them before they start to be a concern. They want inspection to change as little as possible, with as few new tools and techniques as they need, to keep the airlines from seeing it as a maintnance/retraining nightmare. The fact that it makes the whole thing far more robust than a similar sized metal component, (with added strength to boot) is just gravy.
There are 10 kinds of people in the world; those who understand binary, and those that don't.
 
dl757md
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RE: 787 Repairs

Mon Sep 18, 2006 5:08 am

Quoting Remcor (Reply 13):
Quoting EMBQA (Reply 1):
Composites are very easy to repair and are made up of a series of layers. The mechanic will remove ever growing areas of these layers.

Ok, but the original parts are cured in an autoclave (big pressure-cooker). The patch will not be cooked in an autoclave presumably... are the resins that are usued for the patches thus as strong as in the orginal parts? How would you get the air bubbles out of there? I'm sure they've got a way, but I'm wondering how.

The repair is vacuum bagged and heated giving a similar effect as an autoclave. The cooking schedule and vacuum are controlled by the the unit built by Heatcon. The link has some pretty cool info on composite repair processes and equipment. The SRM (structural repair manual) has specifications on the settings you put into the machine and it does the rest. It's really not that difficult and in many cases much faster than repairs of similar damage in sheetmetal.

One other advantage that I've seen in composite repair to this point is that I've never had to get engineering involved in a repair. They slow everything down to a snails pace. The SRM has always had a repair applicable to the damage I've encountered. Often times that isn't the case with ground damage on aluminum structures. If Boeing includes most damage scenarios in the SRM then it will keep downtime on composite repairs to a minimum.

I don't think the issue here is the ability to repair damage to the 787 rather it is the ability to identify damage to the 787.

DL757Md
757 Most beautiful airliner in the sky!
 
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Stitch
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RE: 787 Repairs

Mon Sep 18, 2006 6:25 am

Quoting Kaneporta1 (Reply 11):
I never mentioned a manufacturer in my post. But my estimation is that the fuselage gets banged more than the wings, tailplane and fin.

True, but since a number of other folks have brought this question up on a regular basis to imply that CFRP could be/will be a maintenance nightmare for 787 operators, I just wanted to note for the record that Airbus also intends to increase structural use of CFRP on the A350 and A320RS programs, so therefore any issues with the materials will not be limited to the 787 family.
 
LMP737
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RE: 787 Repairs

Mon Sep 18, 2006 10:58 pm

Quoting Keesje (Reply 9):
No, composites are relatively hard to repair, no reason for denial.

Does this come from actual experinece in composite repair?
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keesje
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RE: 787 Repairs

Mon Sep 18, 2006 11:26 pm

Quoting LMP737 (Reply 17):
Quoting Keesje (Reply 9):
No, composites are relatively hard to repair, no reason for denial.

Does this come from actual experinece in composite repair?

Yes. Even used the hammer on a 787 panel. With composites it's all about process control (tooling, facilities), unpredictable properties and skilled people.

I think most people that ever worked with those composites know it. The authorities know it.

People making a dent in a plate in a labatory and some skilled professional doing a quick repair on a table in a labatory is something completely different then doing a damage check after a catering truck out on a rainy cold platform in Africa or Siberia.
"Never mistake motion for action." Ernest Hemingway
 
Lemurs
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RE: 787 Repairs

Mon Sep 18, 2006 11:50 pm

Quoting Keesje (Reply 18):
People making a dent in a plate in a labatory and some skilled professional doing a quick repair on a table in a labatory is something completely different then doing a damage check after a catering truck out on a rainy cold platform in Africa or Siberia.

You'd think that both A & B would be experts at useability design work at this point. In past years you designed the airplane first, then figured out how people would work on it later. That all seemed to have changed with the 777 and the A380 though, where airlines were involved from the get-go. I am inclined to believe that Boeing had good answers to hard questions when the head of maint for various airlines came in and asked about exactly these things.

I don't have any proof of this of course, other than the fact that Boeing went out of their way to accomodate the maint concerns of airlines in the 777 design from very early on. If they can't make a patch kit that is useable by average maint workers in most conditions, they won't have convinced many airlines about the ability of the airplane to not become a hangar queen. If they DID manage to fool dozens of airlines, that means those airlines were all full of gullible idiots...or Boeing has a good story they feel they can deliver on. I tend to apply Occam's Razor to these scenarios, and while dozens of airlines full of idiots is tempting, it's probably not the simpler of two explanations.  Wink
There are 10 kinds of people in the world; those who understand binary, and those that don't.
 
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antoniemey
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RE: 787 Repairs

Mon Sep 18, 2006 11:53 pm

Quoting Lemurs (Reply 19):
and while dozens of airlines full of idiots is tempting

Idiots, yes, but not that big of idiots... especially not since Continental bought a bunch of 787s.
Make something Idiot-proof, and the Universe will make a more inept idiot.
 
deltadc9
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RE: 787 Repairs

Tue Sep 19, 2006 12:21 am

Quoting Keesje (Reply 9):
In a labatory environment it isn´t easy

Carbon fiber is repaired every day in auto body shops and aircraft maintenance bays all over the world. It is a well understood material that has been in use a long time. JUST NOT MUCH IN CIVIL AVIATION.

The posts in here that imply that this is somehow new or that there is still guesswork involved are misinformed.

By the way, if you want to see how well carbon fiber holds up on impact, check out a wrecked C6 Corvette if you can. Pretty impressive, the hood of my Vette actually saved my life and my wife's when we slid under a fallen suspended tree over the road.The hood forced the tree up and over instead of into the windshield.

BTW, the hood was repairable despite the fact that the Vette was totalled. It had gouges but no cracks.
Dont take life too seriously because you will never get out of it alive - Bugs Bunny
 
keesje
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RE: 787 Repairs

Tue Sep 19, 2006 12:55 am

Quoting DeltaDC9 (Reply 21):
Carbon fiber is repaired every day in auto body shops and aircraft maintenance bays all over the world. It is a well understood material that has been in use a long time. JUST NOT MUCH IN CIVIL AVIATION.

And why is that?
"Never mistake motion for action." Ernest Hemingway
 
Lemurs
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RE: 787 Repairs

Tue Sep 19, 2006 1:14 am

Quoting Keesje (Reply 22):
And why is that?

Well at least one very important reason is that *creating* oversized CFRP parts is not easily done on a mass production scale. Notice that has nothing to with the ability to repair those parts once they have been made. So your question that is obviously begging us to infer an answer (because it's difficult to repair!) really doesn't answer anything.
There are 10 kinds of people in the world; those who understand binary, and those that don't.
 
deltadc9
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RE: 787 Repairs

Tue Sep 19, 2006 2:05 am

Quoting Keesje (Reply 22):
And why is that?

Because it is widely used and has been for quite a while.
Dont take life too seriously because you will never get out of it alive - Bugs Bunny
 
TeamAmerica
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RE: 787 Repairs

Tue Sep 19, 2006 3:28 am

Quoting Kaneporta1 (Reply 3):
The answer is yes. One big disadvantage of CFRP is the NVD, Non Visible Damage, susceptibility. A truck may run crash onto an airplane without causing any external visible damage on the surface, but the impact may cause cracks or delamination inside the material. If this goes unnoticed for a while, it could mean trouble.



Quoting Keesje (Reply 9):
No, composites are relatively hard to repair, no reason for denial. Extra layers don´t stop catering trucks and can even increase the chances of delamination. The FAA and JAA and airlines will have to be satisfied. Luckely Boeing isn´t underestimating.

Too much emphasis on delamination. Boeing is using a relatively new process where the structure is built up in a tape-laying process. This process inherently limits the extent of delaminations, unlike the older method where complete sheets of carbon fiber were being laminated. Local delamination can occur, but it is much less likely to lead to progressive failure.
Failure is not an option; it's an outcome.
 
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zeke
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RE: 787 Repairs

Tue Sep 19, 2006 3:49 am

Quoting TeamAmerica (Reply 25):
Too much emphasis on delamination. Boeing is using a relatively new process where the structure is built up in a tape-laying process. This process inherently limits the extent of delaminations, unlike the older method where complete sheets of carbon fiber were being laminated. Local delamination can occur, but it is much less likely to lead to progressive failure.

Nothing new about this at all, Airbus has been using this process on aircraft for some time (i.e. 330/340/380) and Boeing on the 777. Boeing has about half of the tape laying machines in the world, with a lot of them being used on military projects. Airbus has three sites in Spain doing this sort of work.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
TeamAmerica
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RE: 787 Repairs

Tue Sep 19, 2006 3:59 am

Quoting Zeke (Reply 26):
Nothing new about this at all, Airbus has been using this process on aircraft for some time (i.e. 330/340/380) and Boeing on the 777.

I might well be wrong, but I hadn't heard of either Boeing or Airbus using tape-layup for large structures before this (on civil aircraft). Does anyone have a source for specific production methods used for various structures on A330/340/380? From what I recall, all previous large composite structures have been built-up from sheets. Please correct me if I'm mistaken.
Failure is not an option; it's an outcome.
 
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zeke
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RE: 787 Repairs

Tue Sep 19, 2006 4:17 am

Quoting TeamAmerica (Reply 27):
Please correct me if I'm mistaken.

You are mistaken.

Airbus tape layer production parts include....
A330 and A340 (inc A346) horizontal stabilizer skins (9m long and 2m wide)
A380 horizontal stabilizer skins (16m long and 4m wide)
A380 torque box with automated tape layer skins.
A380 empennage skins
A319/A320/A321 tail were manufactured by hand lay up was changed to automated tape laying.
Military parts for the A400

Boeing used the process on the 777 for the fabrication of the horizontal and vertical stabilizer skin panels, they have on the military front also built the Navy A6 Intruder composite wing using the process.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
TeamAmerica
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RE: 787 Repairs

Tue Sep 19, 2006 4:34 am

Ok - thanks for that, Zeke. I joined A.Net to learn.  thumbsup 

Now, what is the history of delaminations (or other modes of failure) in the tape-laid parts vs. similar lay-ups manufactured from sheets?
Failure is not an option; it's an outcome.
 
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zeke
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RE: 787 Repairs

Tue Sep 19, 2006 4:43 am

Quoting TeamAmerica (Reply 29):
Now, what is the history of delaminations (or other modes of failure) in the tape-laid parts vs. similar lay-ups manufactured from sheets?

I dont think any hard and fast data is out on that. Semi-monocoque tape layered parts in my view would be miles ahead in terms of strength and maintenance over traditional skin and core of the past. A lot of sails on fast yachts these days are made using a similar process, they do suffer from being folded up when not in use.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
glacote
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RE: 787 Repairs

Tue Sep 19, 2006 11:56 am

Quoting TeamAmerica (Reply 25):
This process inherently limits the extent of delaminations, unlike the older method where complete sheets of carbon fiber were being laminated. Local delamination can occur, but it is much less likely to lead to progressive failure.

Could you elaborate on this one? My recollection is exactly the contrary - that taped carbon works in tension only hence breaking fibers significantly loosens the whole structure.

I believe their wide use in competition sailing is a good example. Work in tension only.

This is (if I understand correctly) where the whole bet is: make a whole fuselage section out of it carbon taped fibers. Both the manufacturing process must be perfect (no bubbles, no broken fiber; or you need to add yet more layers) and repairing process, both for detecting and patching.

The main (and huge imho) difference between Airbus and Boeing use of CRFP is that Airbus ones do not really work in tension outside of keeping their shape. But the B787 fuselage does and can not afford to fail on this.

My understanding is that Airbus believes that it is not feasible to ensure reliable mechanical integrety unless you over-engineer the fuselage so much that it gets nearly as heavy as a latest-tech metal fuselage. Their head claimed something around savings < 500kg for a whole plane making it practically useless.

I would bet that the main reason Boeing went on the composite fuselage is the expected low construction costs.

PS: before any more Airbus-just-don't-know-how-to-do-it bashing please recall that 1) Airbus does use the process for large parts already 2) the largest composites parts (wings) are manufactured in Japan with machines developed and assembled in France...
 
zvezda
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RE: 787 Repairs

Tue Sep 19, 2006 3:47 pm

Quoting Glacote (Reply 31):
Could you elaborate on this one? My recollection is exactly the contrary - that taped carbon works in tension only hence breaking fibers significantly loosens the whole structure.

Delamination does not involve the breaking of fibres. It involves the failure of the resin holding layers of fibre together.

Quoting Glacote (Reply 31):
Both the manufacturing process must be perfect (no bubbles, no broken fiber; or you need to add yet more layers) and repairing process, both for detecting and patching.

Boeing are adding redundant layers. Based on what they learn with the B787-8, they should be able to better optimize the B787-9, B787-10, and subsequent models, not to mention the B737RS.

Quoting Glacote (Reply 31):
Their head claimed something around savings < 500kg for a whole plane making it practically useless.

Even if that were true (comparing the OEW for the A350 and B787 suggests that the weight savings is much greater), 500kg of additional payload per flight provides a lot of additional revenue over the life of an airliner.

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