The Boeing 787... Cool aircraft, but is it a bit too ambitious?
04-01-2006, 09:43 AM
#1
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The Boeing 787... Cool aircraft, but is it a bit too ambitious?
Hello all again... I guess I've been thinking lately about the Boeing 787 as I've started my research in composite materials. Anyway from what I've studied composites are quite difficult to repair without compromising strength and toughness, they are not really as isotropic as metals (uniform in properties in all directions of the material), and are quite expensive when you get into exotic aerospace laminates.
It is my understanding that Boeing has done its own research on composites (probably with data obtained through miltary and space craft designs). However, if I understand correctly this will be the first time in aviation history where the entire fusalage of a commerical airliner will be made entirely of composites. Now that concerns me a little because not only is this a vastly different animal than say a fighter aircraft body (which undergoes extreme loading conditions, but is unpressurized and relatively easier to engineer IMHO because of its small size and singular usage). In a commerical aircraft fusalage you not only have the loading every other aircraft encounters, but also pressurization cycling... not to mention those large windows and doors that could lead to high stress concentrations. And yes, composites have been used as pressure vessels (gas canisters), but those are pretty simple cylindrical shapes with simple loadings.
Yes, the commercial aircraft manufacturing industry has used composite materials for years on the order of 10% - 30% composites... but these have been mostly used for non-load bearing parts like panel coverings etc. I believe airbus uses composite control surfaces with honeycomb interiors, but those have been under regulator scrutiny as of late.
My professor says that in all likelyhood Boeing has developed "advanced aerospace composites" that give favorable testing results, but as far as how they accomplish such a feat, he still remains clueless.
Still there is the matter of composite laminate damage testing, and how unless newer more riggorous techniques to test composite damge is developed and standardized in the aircraft industry we could see a great deal of problems with the Boeing 787. Micro cracking anywhere on the fusalage can lead to moisture intrusion and moisture weakening of the general area in between composite layer.
I guess from the airline standpoint, sure they'll be saving money by flying lighter, longer-range aircraft, but at what cost? Aircraft incursions with ground vehicles are not uncommon and if such ground equipment bumps into a 787, the resulting damage may be huge because I really don't think you can "patch" a composite material like you would a metal part, you have to replace the entire thing to maintain stuctural integrity. So an aircraft encountering a mild ground incursion would be written off or go through extensive repairs (replacing entire sections of the aircraft).
I'm surprised people haven't been concerned about these things before. This is a HUGE leap of faith on the part of Boeing in the usage of composite materials. I really hope they've got their bases covered.
It is my understanding that Boeing has done its own research on composites (probably with data obtained through miltary and space craft designs). However, if I understand correctly this will be the first time in aviation history where the entire fusalage of a commerical airliner will be made entirely of composites. Now that concerns me a little because not only is this a vastly different animal than say a fighter aircraft body (which undergoes extreme loading conditions, but is unpressurized and relatively easier to engineer IMHO because of its small size and singular usage). In a commerical aircraft fusalage you not only have the loading every other aircraft encounters, but also pressurization cycling... not to mention those large windows and doors that could lead to high stress concentrations. And yes, composites have been used as pressure vessels (gas canisters), but those are pretty simple cylindrical shapes with simple loadings.
Yes, the commercial aircraft manufacturing industry has used composite materials for years on the order of 10% - 30% composites... but these have been mostly used for non-load bearing parts like panel coverings etc. I believe airbus uses composite control surfaces with honeycomb interiors, but those have been under regulator scrutiny as of late.
My professor says that in all likelyhood Boeing has developed "advanced aerospace composites" that give favorable testing results, but as far as how they accomplish such a feat, he still remains clueless.
Still there is the matter of composite laminate damage testing, and how unless newer more riggorous techniques to test composite damge is developed and standardized in the aircraft industry we could see a great deal of problems with the Boeing 787. Micro cracking anywhere on the fusalage can lead to moisture intrusion and moisture weakening of the general area in between composite layer.
I guess from the airline standpoint, sure they'll be saving money by flying lighter, longer-range aircraft, but at what cost? Aircraft incursions with ground vehicles are not uncommon and if such ground equipment bumps into a 787, the resulting damage may be huge because I really don't think you can "patch" a composite material like you would a metal part, you have to replace the entire thing to maintain stuctural integrity. So an aircraft encountering a mild ground incursion would be written off or go through extensive repairs (replacing entire sections of the aircraft).
I'm surprised people haven't been concerned about these things before. This is a HUGE leap of faith on the part of Boeing in the usage of composite materials. I really hope they've got their bases covered.
04-01-2006, 12:00 PM
#2
Gets Weekends Off
Joined APC: Dec 2005
Position: FO, looking left
Posts: 1,057
It seems like you have two concerns about composite materials.
1. The strength after repeated pressurizations
2. Fixing damage to the fuselage
I am by no means a material scientist, and that was probably my worst subject in college. So I am going to defer the second question to a good friend of mine at Raytheon who knows a lot about composite materials. I will let you know what he has to say.
As for question one, I have no doubt that the 787 will be able to withstand the stresses of constant pressurization/depressurization. When I worked for Adam aircraft designing the A-500 and A-700, we needed to pressurize the aircraft to 24PSI just to get it certified for 8PSI (which is far greater than it will ever experience). (I actually have a cool story about the A-700 tested at 21PSI when I saw the exit door blew off at 400mph!!). I am sure the standards are the same for large commercial jets. We enginners bring those things to the point of failure, and that happens at a point much higher than it can ever possibly experience.
I actually can think of a MAJOR advantage for using composite material with respect to pressurization stress. Remember the Aloha flight about 10 years ago that lost its entire roof? Why? Because it was an old aircraft, flown from sea level to altitude, back to sea level every hour all day long for years. The salt in the air in Hawaii and stress finally got to it, causing the aircraft to loose its roof in flight. My understanding is that these composite materials do not have the same properties as aluminum and such when mixed with salt. Besides, the 787 will be flown on longer routes, and therefore it will experience a lot fewer pressurization cycles over its lifetime.
One other comment. I am not 100% sure (I may be wrong), but isn't the Boeing 777's wing made of composites. I remember seeing video of engineers bending the wind 38ft vertically before it snapped. Now that is STRONG! Not like the A380's wing which snapped at 23ft (and its longer than the 777 wing).
I will find out about damage and replacing composite materials after some sort of collision.
Hope this helps.
1. The strength after repeated pressurizations
2. Fixing damage to the fuselage
I am by no means a material scientist, and that was probably my worst subject in college. So I am going to defer the second question to a good friend of mine at Raytheon who knows a lot about composite materials. I will let you know what he has to say.
As for question one, I have no doubt that the 787 will be able to withstand the stresses of constant pressurization/depressurization. When I worked for Adam aircraft designing the A-500 and A-700, we needed to pressurize the aircraft to 24PSI just to get it certified for 8PSI (which is far greater than it will ever experience). (I actually have a cool story about the A-700 tested at 21PSI when I saw the exit door blew off at 400mph!!). I am sure the standards are the same for large commercial jets. We enginners bring those things to the point of failure, and that happens at a point much higher than it can ever possibly experience.
I actually can think of a MAJOR advantage for using composite material with respect to pressurization stress. Remember the Aloha flight about 10 years ago that lost its entire roof? Why? Because it was an old aircraft, flown from sea level to altitude, back to sea level every hour all day long for years. The salt in the air in Hawaii and stress finally got to it, causing the aircraft to loose its roof in flight. My understanding is that these composite materials do not have the same properties as aluminum and such when mixed with salt. Besides, the 787 will be flown on longer routes, and therefore it will experience a lot fewer pressurization cycles over its lifetime.
One other comment. I am not 100% sure (I may be wrong), but isn't the Boeing 777's wing made of composites. I remember seeing video of engineers bending the wind 38ft vertically before it snapped. Now that is STRONG! Not like the A380's wing which snapped at 23ft (and its longer than the 777 wing).
I will find out about damage and replacing composite materials after some sort of collision.
Hope this helps.
04-01-2006, 02:52 PM
#3
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Originally Posted by ryane946
I actually can think of a MAJOR advantage for using composite material with respect to pressurization stress. Remember the Aloha flight about 10 years ago that lost its entire roof? Why? Because it was an old aircraft, flown from sea level to altitude, back to sea level every hour all day long for years. The salt in the air in Hawaii and stress finally got to it, causing the aircraft to loose its roof in flight. My understanding is that these composite materials do not have the same properties as aluminum and such when mixed with salt. Besides, the 787 will be flown on longer routes, and therefore it will experience a lot fewer pressurization cycles over its lifetime.
Your example also brings another question to mind... how will the 787 do in those super hot conditions you would find in the middle east and around the equator? It is my understanding that composite aircraft are painted white to mitigate heat absorption, however I believe several african, middle eastern, and some southeast asian carriers have ordered the 787 and they all have fancy, non-white paint schemes. The last thing you want is for the matrix of the composite laminates to get soft on you in those sorts of enviornments.
One other comment. I am not 100% sure (I may be wrong), but isn't the Boeing 777's wing made of composites. I remember seeing video of engineers bending the wind 38ft vertically before it snapped. Now that is STRONG! Not like the A380's wing which snapped at 23ft (and its longer than the 777 wing).
Last edited by Imeneo; 04-01-2006 at 02:54 PM.
04-01-2006, 04:17 PM
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I wish.....
I wish I had his smarts. But His point makes sense. Like putting a milk jug in the hot sun. It goes soft after a while. But I am sure they are probably using a composit that can withstand High temp. But again......that milk jug.......
Last edited by Newguy85; 04-01-2006 at 08:06 PM.
04-01-2006, 04:59 PM
#6
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: DISCLAIMER : I have no proper training in this subject area
Im confident that Boeing has deep enough pockets to thouroughly test this crap before puting 250 people inside of it. Of all the companies in the world that deal with composit materials, Boeing has got to be the most experienced by far! All good stuff above, but at the rate with which aircraft have advanced, this is only the most logical next step. I think composit frames are less mind boggling than the though of a jet engines must have been in 1945.
Its time.
Im confident that Boeing has deep enough pockets to thouroughly test this crap before puting 250 people inside of it. Of all the companies in the world that deal with composit materials, Boeing has got to be the most experienced by far! All good stuff above, but at the rate with which aircraft have advanced, this is only the most logical next step. I think composit frames are less mind boggling than the though of a jet engines must have been in 1945.
Its time.
04-21-2006, 01:33 AM
#8
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Joined APC: Apr 2006
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Posts: 12
Even more incredible to me is the elimination of pnuematics and the majority of hydraulics. Electric A/C packs, electric starters, electric brakes and electric leading edge heat to name a few. After reading some of the reasoning on a Boeing release, basically they said that pnuematics had reached nearly the pinnacle of efficiency for those type systems. Electrics however were just now entering a period of great advance and had the most future potential for efficiency gains.
Just as the A380 will need some obvious airport upgrades to accomodate, so shall the B787 require mods to provide the electrical demands an "all electric" commercial jet will create.
It will be an amazing machine and I'm sure there will be growing pains but as fuel prices go up, so does Boeing's stock as more and more carriers look for efficiency.
Due to Boeings recent debaucle with the Air Force tanker and their stained reputation from that ugly episode, the company has gone full force to set a corporate culture of accountability and ethical standards. They can not afford to allow anything to come to the market place not ready. Therefore, from a business persective, if they are not sure the composites are ready for any potential exposure, I don't feel they will field it.
Since the proprietary information on the technology is a closely held secret, this is of course speculation on my part. Just a reasonable guess. Cheers!
Just as the A380 will need some obvious airport upgrades to accomodate, so shall the B787 require mods to provide the electrical demands an "all electric" commercial jet will create.
It will be an amazing machine and I'm sure there will be growing pains but as fuel prices go up, so does Boeing's stock as more and more carriers look for efficiency.
Due to Boeings recent debaucle with the Air Force tanker and their stained reputation from that ugly episode, the company has gone full force to set a corporate culture of accountability and ethical standards. They can not afford to allow anything to come to the market place not ready. Therefore, from a business persective, if they are not sure the composites are ready for any potential exposure, I don't feel they will field it.
Since the proprietary information on the technology is a closely held secret, this is of course speculation on my part. Just a reasonable guess. Cheers!
04-21-2006, 06:17 AM
#9
The NeverEnding Story
Joined APC: Sep 2005
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The 787 is a remarkable aircraft. All electric EVERYTHING. I think each generator will provide 200 kVa (two per engine, and maybe two on the APU), more than an entire 727!!! IIRC from the ASTW article a few months back, one generator will provide plenty of power for its systems in an emergency after shedding non-essential stuff.
Composities aren't as easy as metal to repair, but after watching Cirrus engineers do their stuff with a damaged SR22, I'm fully confident Boeing will have MRO procedures down pat with their airframe.
Still waiting on that Boeing KC-767 (777?) replacement for the KC-135...
Composities aren't as easy as metal to repair, but after watching Cirrus engineers do their stuff with a damaged SR22, I'm fully confident Boeing will have MRO procedures down pat with their airframe.
Still waiting on that Boeing KC-767 (777?) replacement for the KC-135...
04-21-2006, 06:44 AM
#10
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Joined APC: Jan 2006
Posts: 222
I know very little about composites but I am sure Boeing has done its homework. I don't think the plane will "melt" in the hot summer! There are composites out there that have amazing properties.
From the little I know about composites, however, I believe there might be two major problems:
1. Inspection. Apparently cracks, defects and lamination can be internal and not visible from the outside. Also, unlike metal, a very small amount of lamination can turn an extremely strong structure into an extremely weak structure. Special ultrasound equipment is needed for inspection and even then problems might be overlooked. This is particularly a problem for the third world counties – how well do you think they will stick to the inspection schedules? In other words, I'd rather fly in a beat up old metal plane in Africa than in a beat up old composite plane.
2. Aging. It's hard to simulate how these things will age. Putting composite structures through many cycles or otherwise simulating aging is all good but the real test is real aging and there is no shortcut for that. As it stands we know a lot about metal fatigue, and comparatively little about composite fatigue.
From the little I know about composites, however, I believe there might be two major problems:
1. Inspection. Apparently cracks, defects and lamination can be internal and not visible from the outside. Also, unlike metal, a very small amount of lamination can turn an extremely strong structure into an extremely weak structure. Special ultrasound equipment is needed for inspection and even then problems might be overlooked. This is particularly a problem for the third world counties – how well do you think they will stick to the inspection schedules? In other words, I'd rather fly in a beat up old metal plane in Africa than in a beat up old composite plane.
2. Aging. It's hard to simulate how these things will age. Putting composite structures through many cycles or otherwise simulating aging is all good but the real test is real aging and there is no shortcut for that. As it stands we know a lot about metal fatigue, and comparatively little about composite fatigue.
Last edited by sgrd0q; 04-21-2006 at 06:47 AM.
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