columba
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Cargo X Plane By Lockheed Martin Takes Shape

Fri Mar 13, 2009 4:21 pm

As you may know Lockheed is currently building a demonstrator for a new Cargo plane with a composite fuselage based on the Dornier 328Jet
First Pictures of the plane -a new fuselage with the 328Jet Cockpit section - and a full article on this project are here to find:
http://www.aviationweek.com/aw/blogs...918845-aaa6-42f3-adb8-895b2b26d513
It will forever be a McDonnell Douglas MD 80 , Boeing MD 80 sounds so wrong
 
texl1649
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Fri Mar 13, 2009 7:48 pm

Great, they're gonna use this little engineering dem/eval exercise to show how cost-effective their design/carbon barrel process is, on an irrelevant scale, without any constant spec changes from the DoD procurement process, which would make this a 72-month design that would be 10 tons over-weight, and 5x as expensive as advertised (aka, A400M).

The only other things missing are that they should be forced to buy from a conglomerate of Mexican engine component manufacturers who have never seen a Do-328 JET, and a fight between Ga. and Ft. Worth about where the wings get produced..
 
GST
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Sat Mar 14, 2009 12:18 pm

I musty say I am sceptical about the usefulness of this test. Dont get me wrong, i really like composites as a material. I think they are perfect for putting round civil airliners anywhere they wont get easily dented (i have no idea why people insist on putting composites near doors, on under wing nacelles etc), as they are a pain to fix, if indeed they are fixable as it dosent take much denting to need a new part.

What i'm not sure about is the 2 piece fuselage skin idea. It strikes me that it is fine as an x plane, just to test the theory, but to roll that out to a millitary transport? It strikes me that military transports will always face the possibility of catching a bullet (especially in places like afganistan or iraq where the air bases can only be secured to a certain distance. It seems senseless to me that a single bullet hole could force the replacement of an entire half of the fuselage skin (and if that is bonded to other componants with adhesives, that could be a monster job). Keep small panels secured in such a way as they can be easily replaced and reduce the risk of an aircraft taking damage that takes weeks to set right. Thats my 2 cents anyway.
 
Alessandro
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Sat Mar 14, 2009 2:12 pm

Will it be pressurized or not?
From New Yorqatar to Califarbia...
 
Spacepope
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Sat Mar 14, 2009 3:37 pm

I like it. GDB your cncern about damage may not be well founded. The vacuum bag and mobile oven idea means that a repair can be done on the skin without disassembly. The complex contour of the rear fuselage would serve to increase strength and rigidity.

I'm actually quite suprised about the "OMG this is new KILL IT WITH FIRE" responses so far.
The last of the famous international playboys
 
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kc135topboom
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Sat Mar 14, 2009 6:22 pm

This could work out to be a very good idea for LM. After all, Boeing is building a full size composet airliner (B-787) and the process of building composit structures is maturing. Fighters have used composits since the F-15/F-16, and the Starship design worked very well, too (but there were other issues with the Starship, IIRC there were some 75 built by Ratheon).
 
GST
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Sun Mar 15, 2009 1:01 am



Quoting Spacepope (Reply 4):

I'm actually quite suprised about the "OMG this is new KILL IT WITH FIRE" responses so far.

Whilst I do not doubt that composites are fantastic materials for aerostructures, and indeed I am actively excited and enthusiastically about the continued rollout of composites all over the industry, I just hope that in potential military transports to be built after this, that they make damned sure they are on the money with the repairability. Yes, the vaccuum bag and oven is as good as it gets for composite repairs, I was not aware it was portable enough to be used in an assembeld structure though. You learn something new every day. Bbut even if it is there will be places on any airframe where you cant get it to. Also I'm not convinced that any repair on a composite given the nature of its structure. 8+ axes of fibresin any composite, orientated specifically to carry the stresses of the component in that specific point. Try to put a patch in it, you need to make damned sure the fibres are in the right direction, and bonded to the fibres in the origional part. If theyre not lined up or connected, you just have the matrix that carries almost no stress at all. Composites are only strong in the directions we design them to be, unlike metals their material properties arent the same in every direction.

Dont get me wrong, I am eager to see sucess for this test bird, I just wouldnt like to see unecessary complication in down the line aircraft.
 
JoeCanuck
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Sun Mar 15, 2009 6:50 am

If CFRP repairs anything like fibre glass, patching shouldn't be much of an issue. Fibre glass repairs end up just as strong as the original.
What the...?
 
GST
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Sun Mar 15, 2009 11:06 am

Quoting JoeCanuck (Reply 7):
If CFRP repairs anything like fibre glass, patching shouldn't be much of an issue. Fibre glass repairs end up just as strong as the original.

The fibreglass most people think of, FRP, is subtly different to CFRP. In FRP the glass fibres are often fed into a rotating drum, and centrifugal force is used to force them into a mat on the sides, to which the bonding matrix is applied and the whole sheet secured to the mould/fix point etc. The resulting structure of this is fibres randomly orientated in direction, making the material reasonably strong in all directions, and as flexible as the moulding shape allows.

In CFRP several planes of fibres are used. In one plane, all fibres are paralel. Often more than 8 planes are used, each with fibres in different directions carrying stresses in different directions. The orientation of these planes is specifically arranged to carry stresses present in the specific part. If a break is made, not only are a large number of fibres severed and made useless, but any fix must be made with planes of fibres pointing in exactly the same direction as those of the damaged part. If this is not done your fix will not be able carry the same forces transmitted to it by the part, and your fix will be purely aerodynamic. Structurally your break will still be there.

[Edited 2009-03-15 04:07:08]
 
bmie70
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Sun Mar 15, 2009 12:12 pm



Quoting GST (Reply 6):
I just hope that in potential military transports to be built after this, that they make damned sure they are on the money with the repairability. Yes, the vaccuum bag and oven is as good as it gets for composite repairs, I was not aware it was portable enough to be used in an assembeld structure though. You learn something new every day. Bbut even if it is there will be places on any airframe where you cant get it to. Also I'm not convinced that any repair on a composite given the nature of its structure. 8+ axes of fibresin any composite, orientated specifically to carry the stresses of the component in that specific point. Try to put a patch in it, you need to make damned sure the fibres are in the right direction, and bonded to the fibres in the origional part. If theyre not lined up or connected, you just have the matrix that carries almost no stress at all. Composites are only strong in the directions we design them to be, unlike metals their material properties arent the same in every direction.

There are "repair units" (trying to remember the proper term) that can be used to repair damaged broken CFRP laminates in situ. These basically are a vacuum pump and heater mats that come in a flight case about the size of a large carry-on bag. The heater mats can be anything from 10cm2 to 1m2 depending on the area that needs to be repaired. Repairs of CFRP are relatively easy as long as the repair area has been properly prepared i.e. cleaned with solvent to remove contaminants and scarfed to give a smooth transition between the repaired section and the existing laminate (this reduce the risk of introducing any stress concentration). Aligning the fibres isn't too dificult as it is possible to align them with the fibres of the existing laminate at the scarfed edges.

In terms of there being places on the airframe that you can't access, surely this is also the case in alloy airframes (and possibly worse as there is more framing)?
 
texl1649
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Mon Mar 16, 2009 9:59 pm

First, you really can't repair the carbon frames being built now by Boeing a la 787. Second, carbon frames shouldn't be just designed identically as with aluminum. Until engineers doing the design/CAD work understand how to maximize the material, the theoretical gains vs. real-world weight/cost gains delta will persist.

The simple truth is, that while LM has a ways to catch up in fabrication vs. EADS/Boeing here, this little exercise (in identical shape etc. vs. aluminum) is almost a demonstration of their competitor's design/mfg limitations at present vs. a competitive breakthrough.
 
JoeCanuck
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Mon Mar 16, 2009 10:24 pm



Quoting Texl1649 (Reply 10):
First, you really can't repair the carbon frames being built now by Boeing a la 787

Really? i find that very surprising.
What the...?
 
Oroka
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Tue Mar 17, 2009 3:33 am

Pretty sure the carbon parts Boeing is using can be repaired... it is a FAA requirement, and a good selling point. What is the point if you cant even repair ramp rash?
 
rheinwaldner
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Tue Mar 17, 2009 9:29 am

Very interesting is the shell concept. I assume this will be the future.

My prediciton to play with the fire is that the 787 is the first and last airplane with the barrels. I am patiently waiting until the next comes to be disproved. Further info here:
http://www.airliners.net/aviation-forums/tech_ops/read.main/216974/

The Cargo X demonstrator realizes the following points from my proposal:
1) Using panels or shells
2) Integration of stringers into the shell without fasteners (in this case there are no stringers but the related strength is gained from the sandwich structure)
3) Structure elements bounded (=co cured) to the skin (here the pi-joints which hold the few frames)

Point 2 and 3 would not be possible with the 787 design.
 
keesje
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Tue Mar 17, 2009 3:14 pm

Interesting devlopment, no doubt steap learning curves.

All financed by the DOD. This is the kind of massive subsidiezing the EC is using in their case..

IMO the absense of stringer and frames could make repairs easier. They don't break (being absent) and you can add them later when neccessary for a repair..The (no doubt thick) sandwich absorbs a lot of energy too, often preventing damage to the inner skin.

"Never mistake motion for action." Ernest Hemingway
 
rheinwaldner
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RE: Cargo X Plane By Lockheed Martin Takes Shape

Tue Mar 17, 2009 3:51 pm



Quoting Keesje (Reply 14):
The (no doubt thick) sandwich absorbs a lot of energy too, often preventing damage to the inner skin.

Airbus developed a similar concept with a very thin outer skin. As long as visible inspection reveals no damage (e.g. dent) the structure can be considered intact. An intact fragile outer skin working as structure integrity confirmation.

Would solve the problem of detecting potential damages.

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