Revo1059
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Safety of CFRP-constructed 787?

Fri May 20, 2011 8:48 pm

Let me make this perfectly clear, this is NOT a dig at BOEING at all.


I love flying and have never been fearful of it.......but.......

The 787 is a completely new way of making a plane and what it is made of. With the current metal planes having been around for as long as they have most of the kinks have been worked out. A CF passenger plane does make me a little wary of how it will hold up long term and how it will tolerate various stresses.

One thing that comes to mind is the Southwest plane that lost some skin or the UA plane that blew out part of it's fuselage. Metal stresses differently, it can actually bend, stretch and give signs before it fails. I don't believe CF can do that. It's either intact or in a million pieces. Experts have decades of real world data on how todays planes react as they age and that has come from some hard lessons learned.

I'm not afraid (way too strong of a word)per se, and when I have the chance to ride the 787 I will gladly take my seat, but with such a new way of building a plane and the materials used, it does make me wonder just a little bit........
 
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Stitch
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Safety of CFRP-constructed 787?

Fri May 20, 2011 9:01 pm

Well we've had large composite structures in military planes for some time and they seem to hold it together, so I'm not going to worry about it. CFRP, Al or wood and fabric, it's out of my hands, anyway.  
 
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par13del
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Safety of CFRP-constructed 787?

Fri May 20, 2011 9:18 pm

Well that's one less person to ride on the A380, my chances have improved.  

You do know that prior to the 787 the largest piece of composite material was in the A380 right, and no it was not involved in the QF incident.
 
XT6Wagon
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Safety of CFRP-constructed 787?

Fri May 20, 2011 10:02 pm

you have been riding in planes that would crash with the failure of thier composite structures for decades now.

Vertical and horizontal stabilizers have been composite for quite some time.
 
JBirdAV8r
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Safety of CFRP-constructed 787?

Fri May 20, 2011 10:30 pm

Quoting revo1059 (Thread starter):
Metal stresses differently, it can actually bend, stretch and give signs before it fails. I don't believe CF can do that. It's either intact or in a million pieces.

That's not exactly true.

Carbon Fibre Reinforced Polymer, while never used to the extent that it is on the 787, has been used by Airbus, Boeing and most other aviation manufacturers for decades on more critical parts than the fuselage. You find them in jet fighters that can easily take many times the loads ever expected in a commercial jetliner--and they've been in service for many years.

In my experience (maybe it's just me) people think of CFRP the same way they think of fiberglas. And this is most definitely NOT fiberglas.
I got my head checked--by a jumbo jet
 
nomadd22
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Safety of CFRP-constructed 787?

Fri May 20, 2011 10:43 pm

There's a reason they've been torturing two test frames. The static frame held up to more than any plane will ever see short of crashing and they'll continue to abuse the fatigue frame until it's had more bending and stretching than Joan Rivers' face. They don't just pick a new hull and start flying passengers on it.
And your logic is a little peculiar, since both incidents you referred to are proof that you often have no warning whatsoever of aluminum failure.
Anon
 
goblin211
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Safety of CFRP-constructed 787?

Fri May 20, 2011 10:45 pm

Quoting JBirdAV8r (Reply 4):
. And this is most definitely NOT fiberglas.

If it was, I sure as heck wouldn't risk my life on it, not that the FAA would even approve such a thing.
Think of it this way revo1059, if it wasn't safe the FAA wouldn't approve of it and there wouldn't be any testing.
From the airport with love
 
mrskyguy
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Safety of CFRP-constructed 787?

Fri May 20, 2011 10:53 pm

I don't mean to rain on the OP's parade, but isn't this thread just a bit of a step in to the ridiculous? The 787's up to 1,266 flights and 3,501 hours. The A380's been flying since April of 2005. And decades before that, CFRP has been used in many applications in aircraft.
"The strength of the turbulence is directly proportional to the temperature of your coffee." -- Gunter's 2nd Law of Air
 
tdscanuck
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Safety of CFRP-constructed 787?

Fri May 20, 2011 11:25 pm

Quoting revo1059 (Thread starter):
The 787 is a completely new way of making a plane and what it is made of.

It's only new for commercial aircraft...the material and style of construction is decades old.

Quoting revo1059 (Thread starter):
A CF passenger plane does make me a little wary of how it will hold up long term and how it will tolerate various stresses.

The 777 uses exactly the same materials in its tail (one of the more highly loaded structures on the plane) and floor and is going on 15 years. It's "new" that the material is now being used for fuselage skin but, to some extent, stress is stress so the material properties and aging are *very* well characterized by now.

Quoting revo1059 (Thread starter):
One thing that comes to mind is the Southwest plane that lost some skin or the UA plane that blew out part of it's fuselage.

That's actually a type of failure that's nearly impossible to have in composites.

Quoting revo1059 (Thread starter):
Metal stresses differently, it can actually bend, stretch and give signs before it fails. I don't believe CF can do that. It's either intact or in a million pieces.

CFRP can bend and give signs before it fails. It does stretch, but elastically. The major difference between CFRP and aerospace alloys is that CFRP has a very small gap between yield strength (where it starts to permanently deform) and ultimate strength (where it breaks). But, since all aircraft design is done assuming that you never go above yield strength in the life of the aircraft, there shouldn't be any noticeable different in material behavior in normal use. It's only *after* you overstress the airframe that the differences show up.

Quoting revo1059 (Thread starter):
Experts have decades of real world data on how todays planes react as they age and that has come from some hard lessons learned.

This is equally true of CFRP as it is for alloys. From a pure materials standpoint, the GLARE on the A380 is more risky than the CFRP on the 787 or A350. I'm *not* suggesting there's anything wrong with GLARE, just that's it's got a much smaller history in aviation use than CFRP.

Tom.
 
FX1816
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Safety of CFRP-constructed 787?

Fri May 20, 2011 11:29 pm

Quoting revo1059 (Thread starter):
or the UA plane that blew out part of it's fuselage.

Do you mean the UA 747 that had a hole rip open in it after departing HNL? If so I don't really believe that the type material the fuselage is made of would matter at all in this case given that an electrical short caused the door to open up in mid flight and that is why it ripped a hole in the plane.

FX1816
 
eastern747
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Safety of CFRP-constructed 787?

Fri May 20, 2011 11:40 pm

We have to remember the very first aircraft were wooden timbers held together with wire......the next generation, I believe was a wood frame covered in canvass.....then on to tin and eventually steel aluminmum etc. I'm always amazed that everytime I board an aircraft, I look at the door frame and see how thin the skin really is. I believe it's time to move on and search for new products that mean greater safety and economics.I remember in the 50's-60's-70's having to buy a car every 5-6 years because they broke down, rusted, etc. I now drive an 02 car without a single spot of rust. The paint looks brand new and it still has had no problems. (knock on wood). My point is these new aircraft will carry use to the middle of this century, and with that point change... is good.
 
soon7x7
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RE: Safety Of CFRP-constructed 787?

Sat May 21, 2011 2:10 am

Last month I was given two wingtips from the horizontal stab of a very popular regional jet to topcoat as these were new replacements for eroded carbon fibre older flown ones. I was shocked at the level of leading edge erosion on the used components, almost 80% penetration. Had these leading edges had metallic leading edges I would not have been requested to topcoat new replacements. The closest eroded metallic ecquivalent I have seen was from a 30 year old US Air DC-9 30...not a 5 year old N/G regional. While I highly regard Tdscanuck responses I beg to differ on CFRP's ability to warn of failure...that is the one undesirable characteristic of the material is that when it fails it is usually catastrophic and immediate. While the material has been used in many forms over decades to my knowledge it has never been used to create the torque box of a major transport aircraft such as the 787. While jet fighters, military hilos and various heavy transport aircraft utilize the material, the load demands of a main wing are far different than vertical fins, tail cones,...etc. As much as I love the science of composites, I still believe that over time we will learn once again the limits of certain material applications. By the way...fibre glass is still widely used in the production of transport aircraft. Epoxy is the binder...not polyester resins. One more point...an International council exists that has an annual meeting and produces a book annually that focuses on the limits of fabrication with CFRP's. I purchased the book...much$$$,...I understand about 30% of it as I am not a physicists. Still trying to sort through it but the base concern is that the industry recognizes the materials shortcomings in predictability...in short.
 
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Stitch
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RE: Safety Of CFRP-constructed 787?

Sat May 21, 2011 2:35 pm

Well if CFRP is not safe, the 787 and A350 are going to cause Boeing and Airbus a great deal of grief.

But if both of them liquidate, at least we'll have United Aircraft Corporation to pick up the slack and deliver good ol' aluminum airliners.  
 
soon7x7
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RE: Safety Of CFRP-constructed 787?

Sat May 21, 2011 8:07 pm

I recently read an article in Aviaition Week regarding the production of a Chinese regional jet...the type and name escapes me as I must find the article as some will demand I show" references"...however, the article went on to state that the producers have opted for conventional alloy construction over composites as the weight penalty was neglagable, the production would be easier and less expensive and faster. No doubt that this RJ will have composites in its design but not as primary structure...according to the article. Don't get me wrong...I champion composites as the process is an engineering marvel. What other product takes spools of filament, rolls of fabric, impregnates them with liquid and Bingo!...an aerodynamic, thermal resistent structure that can and will endure incredible punishment. I just believe the product has a limit that no one has quite put their finger on yet, regarding cycles, mass, etc. As primary structures CFRP's in heavy Iron, Uh...heavy plastics, is sort of in its infancy relatively speaking.
 
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Stitch
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RE: Safety Of CFRP-constructed 787?

Sat May 21, 2011 8:25 pm

Quoting soon7x7 (Reply 13):
I recently read an article in Aviaition Week regarding the production of a Chinese regional jet...the article went on to state that the producers have opted for conventional alloy construction over composites as the weight penalty was neglagable, the production would be easier and less expensive and faster.

Probably the Comac ARJ21. And the Comac C919 narrowbody will also be made mostly of aluminum. And for a "new entrant", it makes sense to stick with "known technologies" and not take additional risks with new materials.
 
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SEPilot
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RE: Safety Of CFRP-constructed 787?

Sun May 22, 2011 1:25 am

I believe that CFRP will, if anything, improve crash survivability. Formula 1 cars have incorporated a safety cell made largely of CFRP, and it has proven quite effective. The point is that CFRP will absorb a large amount of energy, and then shatter without significant defomation, while metal will deform to absorb energy and more likely than not crushing any occupants.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
soon7x7
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RE: Safety Of CFRP-constructed 787?

Sun May 22, 2011 12:12 pm

Quoting Stitch (Reply 14):
and not take additional risks with new materials.


Yes, the article stated that having witnessed the "problematic forward motion of major contractors development progress"...they will opt for "conventional alloy construction".

Quoting SEPilot (Reply 15):


In an unfortunate way...it will be interesting to see how your theory plays out in the future...One of my clients currently flies two models from one manufacturer and their pilots state that when landing, the CFRP airframe has a much more pronounced contact with the runway while the alloy airframe is softer. They note that the contact force travels through the entire airframe suddenly rather than softly being absorbed by the conventional airframe (aluminum).

Quoting SEPilot (Reply 15):
while metal will deform


You mean..."the Mercedes Crumple Zones?"...another word for..."we're using thinner guage metals!...I love the spin...   
 
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SEPilot
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RE: Safety Of CFRP-constructed 787?

Mon May 23, 2011 12:09 am

Quoting soon7x7 (Reply 16):
One of my clients currently flies two models from one manufacturer and their pilots state that when landing, the CFRP airframe has a much more pronounced contact with the runway while the alloy airframe is softer.

How much of this is influenced by the fuselage material, and how much by the landing gear design? I'm not saying that the fuselage might not have the effect you describe, but the landing gear tuning might also have a substantial effect. And this does not really mean anything in terms of the performance in a crash.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
aklrno
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RE: Safety Of CFRP-constructed 787?

Mon May 23, 2011 1:22 am

Quoting SEPilot (Reply 15):
I believe that CFRP will, if anything, improve crash survivability. Formula 1 cars have incorporated a safety cell made largely of CFRP, and it has proven quite effective. The point is that CFRP will absorb a large amount of energy, and then shatter without significant defomation, while metal will deform to absorb energy and more likely than not crushing any occupants.

The CFRP tub that the driver sits in neither deforms nor shatters if things go correctly. That is the whole point. The energy is lost by the deformation and then departure of nearly everything attached to the tub. There have been several well publicized crashes of Ferrari Enzos which are built the same way. The drivers walked away. The car was collected from the surrounding area and sent to the dump in small pieces.

Quoting soon7x7 (Reply 16):
Quoting SEPilot (Reply 15):
while metal will deform


You mean..."the Mercedes Crumple Zones?"...another word for..."we're using thinner guage metals!...I love the spin...   

Instead of cynicism, try leaning a little engineering. The crumple zones work beautifully . In the old days when thicker steel was the norm, the death rate was much higher. The car was often repairable by the late driver's estate. As in my comment above, the current idea is for as much energy as possible to be absorbed by the frame. To insure this, the frame has areas where members are intentionally weakened by a bit of accordion folding so that the engineers can choose where the deformation occurs. Thin steel may save some money, but it also allows the crumple to work better.
The car is easily totaled, but more passengers survive.

The lighter steel also makes everything else in the car lighter, making everything cost less and reduces driving costs. Lest someone say that lighter cars are more dangerous, please note the death rates are lower because of things like crumple zones.

Too bad that doesn't work well for airplanes. Too much energy for the amount of frame and a lot of fuel.
 
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bikerthai
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RE: Safety Of CFRP-constructed 787?

Mon May 23, 2011 3:03 pm

Quoting revo1059 (Thread starter):
Southwest plane that lost some skin

The Southwest plane lost some skin because of improperly drilled rivet hole that failed and caused propagation of the failure along the fastener line. With the 787, there are fewer fastener lines to fail and in CFRP cracks do not propagate.

1) Cracks that starts in the matrix usually stops at the fiber/matrix interface.
2) Cracks that breaks a fiber doesn't do a whole lot because in the nature of the composite, the load is sheared into the matrix and around the broken fiber to the other side. (this is why composite is almost immune to fatigue crack propragation)

The one thing you have to worry about is potential delamination and propagation. Specially for bonded stiffeners. This will be proven out the next few years.

The other things that CFRP designer needs to worry about is the corrosion on any aluminum component mating up with CFRP parts. But as other here have noted. This is a known issue and is being addressed through proper galvanic isolation.

bikerthai
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tdscanuck
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RE: Safety Of CFRP-constructed 787?

Mon May 23, 2011 9:52 pm

Quoting soon7x7 (Reply 11):
While the material has been used in many forms over decades to my knowledge it has never been used to create the torque box of a major transport aircraft such as the 787.

777 vertical and horizontal fin, A300/310 (and I think most of the subsequence Airbii) empennage. All primary structure torque boxes. And the loading on the horizontal fin is exactly the same as the wing from a stress point of view.

Tom.
 
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Stitch
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RE: Safety Of CFRP-constructed 787?

Mon May 23, 2011 10:00 pm

A significant part of the A380's wingbox is also made from CFRP. I've stood next to one and it's powerfully impressive (doubly so when they rolled an A320 wingbox up next to it).
 
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bikerthai
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RE: Safety Of CFRP-constructed 787?

Tue May 24, 2011 6:54 pm

Also, composite floor beams seems to be the norm now for large aircraft.

bikerthai
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PolymerPlane
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RE: Safety Of CFRP-constructed 787?

Tue May 24, 2011 7:16 pm

Quoting soon7x7 (Reply 11):
Last month I was given two wingtips from the horizontal stab of a very popular regional jet to topcoat as these were new replacements for eroded carbon fibre older flown ones. I was shocked at the level of leading edge erosion on the used components, almost 80% penetration

The leading edges of 787 will be metal

Quoting soon7x7 (Reply 13):
I recently read an article in Aviaition Week regarding the production of a Chinese regional jet...the type and name escapes me as I must find the article as some will demand I show" references"...however, the article went on to state that the producers have opted for conventional alloy construction over composites as the weight penalty was neglagable

That is only true for smaller aircrafts. IIRC McNerney admitted as much when discussing the 737 replacement.

Quoting SEPilot (Reply 15):
I believe that CFRP will, if anything, improve crash survivability. Formula 1 cars have incorporated a safety cell made largely of CFRP, and it has proven quite effective. The point is that CFRP will absorb a large amount of energy, and then shatter without significant defomation, while metal will deform to absorb energy and more likely than not crushing any occupants.

F1 survivability is related more to the honeycomb structure than the materials itself. CFRP might enable the honeycomb structure production, but the source of the strength is not CFRP
One day there will be 100% polymer plane
 
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SEPilot
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RE: Safety Of CFRP-constructed 787?

Tue May 24, 2011 11:33 pm

Quoting PolymerPlane (Reply 23):
F1 survivability is related more to the honeycomb structure than the materials itself. CFRP might enable the honeycomb structure production, but the source of the strength is not CFRP

I'm not so sure. I see it as a major advantage that CFRP will shatter rather than deform; this enables it to absorb and dissipate energy without collapsing the survival space of the occupants. How many car and aircraft crashes have caused the death of the occupants because they were crushed inside the passenger compartments? With CFRP the structure itself will not be deformed to the point of crushing the occupants; it will shatter instead. The occupants may still be killed by debris, by the force of the collision, or by other means, but I hold that they will have an additional chance of survival.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
aklrno
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RE: Safety Of CFRP-constructed 787?

Tue May 24, 2011 11:57 pm

Quoting SEPilot (Reply 24):
I'm not so sure. I see it as a major advantage that CFRP will shatter rather than deform; this enables it to absorb and dissipate energy without collapsing the survival space of the occupants. How many car and aircraft crashes have caused the death of the occupants because they were crushed inside the passenger compartments? With CFRP the structure itself will not be deformed to the point of crushing the occupants; it will shatter instead. The occupants may still be killed by debris, by the force of the collision, or by other means, but I hold that they will have an additional chance of survival.

I'd like to hear from an engineer who is up to date on crash protection before believing that is correct. The number of pieces that result from the impact says little about the protection offered. The whole point of deformation is that it continues to absorb energy for a longer period (several milliseconds) as opposed to shattering. People aren't usually crushed in the car. The damage is when they suddenly go from 60mph to zero, often by hitting the interior of the car. There is usually plenty of room for crushing. Photos of crashed cars frequently show total destruction up to the A pillar, then little damage except to sheet metal further back. That's what controlled deformation is about. You can shatter a piece of glass with a light tap from a hammer. Little energy is involved. After carbon fiber cracks, no more energy is absorbed.

Honeycomb can be a good cushion because it has a lot of small energy absorbing cells that crush in sequence. They can be made of CFRP, aluminum, or wax, the original honeycomb (if you have enough of them). Airplanes are a problem for protection by deformation because the amount of crushable material would be so heavy or so large that the thing wouldn't get off the ground.
 
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SEPilot
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RE: Safety Of CFRP-constructed 787?

Wed May 25, 2011 12:58 am

Quoting aklrno (Reply 25):
People aren't usually crushed in the car.

On a frontal collision this is usually correct. However, other accidents T-bone and rollovers in particular, often do involve crushing the occupants. And aircraft do not have the crumple zones that cars do.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
tdscanuck
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RE: Safety Of CFRP-constructed 787?

Wed May 25, 2011 2:16 pm

Quoting aklrno (Reply 25):
You can shatter a piece of glass with a light tap from a hammer. Little energy is involved. After carbon fiber cracks, no more energy is absorbed.

After carbon fiber cracks, *lots* more energy can be absorbed. The "shattering" process is really the disbonding of bazillions of fiber/matrix interfaces. Even throughly delaminated CFRP has the ability to continue absorbing energy.

Tom.
 
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bikerthai
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RE: Safety Of CFRP-constructed 787?

Wed May 25, 2011 2:48 pm

Quoting SEPilot (Reply 24):
I see it as a major advantage that CFRP will shatter rather than deform; this enables it to absorb and dissipate energy without collapsing the survival space of the occupants.

From my previous experience, composite (including honeycomb) does absorb a lot of energy. However, the point of failure is really unpredictable (large scatter) so it is difficult to calculate how much energy absorbed and when.

Aluminum honeycomb with aluminum skin does a great job at absorbing energy. That is why it is often used to meet 16G crash requirement for mounting forward facing Attendance seat. Aluminum skin with Nomex core also works for this application. And since aluminum deformation is well known, it is more easily predicted.

With the aluminum skin , local deformation in the skin at stress concentration area (fasteners etc) can absorb a lot of energy before the panel buckles. With composite, you don't have much local deformation before the panel gives way.

bikerthai
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
soon7x7
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RE: Safety Of CFRP-constructed 787?

Thu May 26, 2011 1:19 am

Quoting tdscanuck (Reply 20):
And the loading on the horizontal fin is exactly the same as the wing from a stress point of view.


I compared the Vertical fin loads to Main wing loads...not to H/stabs. However,...H/stabs with their smaller relative area would be better suited for composites, but main wings?...a lot of stuff going on there.

Quoting aklrno (Reply 18):
Instead of cynicism, try leaning a little engineering



A bit sensitive are we?...Believe me, I'm aware of crumple zones...my first car was a 67' Chevy Bel Air wagon. It didn't bend...easily. My Benz does bend,...very easily...$$$

On topic...

I used to fly a Grob Acro ll CF sailplane out at FOK, Long Island. We operated consistently on grass/sand areas, not the concrete runways. The majority of the time we dealt with x winds. We received a bulletin from the manufacturer about flying x wind conditions more than 15 knots. The result would be potentially a snapped off tail boom. While performing inspections we came upon an internal deformation under the gel coat where the CF spar was located on one of the wings. I never saw the ship again but it was replaced by an all metal SGS 2-32. Not as sexy as the Grob, but it handles anything we can throw at it without any worries.
 
XT6Wagon
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RE: Safety Of CFRP-constructed 787?

Thu May 26, 2011 3:43 am

Quoting soon7x7 (Reply 29):
but main wings?...a lot of stuff going on there.

One of the reasons it hasn't been used earlier is that a skin that can take the abuse that wings take... from fueling and other servicing means a skin that is far thicker (and heavier) than required for mere structural needs. So why add weight for increased costs...

Now composites are better and cheaper. It also makes alot more sense when the rest of the plane is composite, even if the wing skin is thicker than optimal for mere strength.
 
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bikerthai
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RE: Safety Of CFRP-constructed 787?

Thu May 26, 2011 1:31 pm

Quoting XT6Wagon (Reply 30):
One of the reasons it hasn't been used earlier is that a skin that can take the abuse that wings take

We all know the efficiency of CFRP, but one thing that has kept CFRP from achieving their touted efficiency on a commercial airline wing is the inability to accurately predict the stress and crack propagation mode at the "noodle" in the skin stringer interface. There were some recent development (relatively speaking) that went a long way to improve the prediction of stresses at the noodle that allowed for both improved design and reduce the data scatter needed for improved allowables.

bikerthai
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
rheinwaldner
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RE: Safety Of CFRP-constructed 787?

Fri May 27, 2011 7:51 am

Quoting SEPilot (Reply 24):
With CFRP the structure itself will not be deformed to the point of crushing the occupants; it will shatter instead.

But where do the shatters go?

Clouds of razor baldes shooting through the cabin may negate the bonus of the "softer" impact....

I think of the Turkish 737 in Amsterdam, but also crashes where some onboard survived, e.g. Swiss in Bassersdorf or even Habsheim. If these fuselages would have disintegrated in small sharp pieces, the overall chances for a partially positive outcome would have been lower IMO.
 
justloveplanes
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RE: Safety Of CFRP-constructed 787?

Fri May 27, 2011 8:53 am

I am still curious about the ability of an all composite airliner to withstand lightning strikes as my primary area of potential concern. I have heard about the testing, simulation, etc.

However, with all the sealant being removed, reapplied, etc, how well will this stuff hold up over 30 years? How tolerant is this desing to an occasional fastener here and there that might separate? What about the QC issue over 100's / 1000's of fasterners?
 
tdscanuck
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RE: Safety Of CFRP-constructed 787?

Sat May 28, 2011 1:02 am

Quoting rheinwaldner (Reply 32):
But where do the shatters go?

They don't really go anywhere..."shatter" isn't the right word. What happens is the matrix comes apart and generally ends up nearly powdered, and the fibers go floppy because there's no matrix to support them.

Quoting rheinwaldner (Reply 32):
Clouds of razor baldes shooting through the cabin may negate the bonus of the "softer" impact....

The fibers tend not to come apart much and they're stuck in the remaining matrix...big bits tend not to go flying.

Quoting justloveplanes (Reply 33):

I am still curious about the ability of an all composite airliner to withstand lightning strikes as my primary area of potential concern. I have heard about the testing, simulation, etc.

It's happened several times. No big deal.

Tom.
 
soon7x7
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RE: Safety Of CFRP-constructed 787?

Sat May 28, 2011 4:14 am

The entire focus of why major transports are currently transitioning to CF structures has only one goal. To create a fuel efficient machine that can transport revenue PAX further for less money. Another words...a better "mouse trap". This line of thinking I personally think is dangerous. I'll get flamed for it...that's OK. I've got my nomex suit on. The trend for obvious reasons, is to produce fuel efficient machines. That is the priority. To achieve certification, of course the airframe must conform too certain criteria. Safety used to be the selling point but no more...economy is the marketing buzz word that commands billions ($$$) in orders. Having said that, I feel design has been leaned out, the envelope pushed, thought outside the box....whatever cliche you decide to attach to the process. I'm not confident about hyper automation in the flight domain nor do I feel terribly secure in plastic machines in hostile environments. That's just me,... and a few others that probably don't want to chime in, but I know your out there...g   
 
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Starlionblue
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RE: Safety Of CFRP-constructed 787?

Sat May 28, 2011 4:33 am

soon7x7, I understand your viewpoint. However I have two comments:

- Certification requirements are tougher than ever. I doubt a 707 or a 727 would be certified today, for example. And "plastic airliners", if you'll forgive the expression, have to pass these requirements.
- The quest for a better mousetrap in aviation has been going on since the early years of the 19th century. There is nothing that special about this particular transition compared to the transitions to pre-stressed skins, aluminum skins, FBW, jet engines, turbofans or closed cockpits.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
tdscanuck
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RE: Safety Of CFRP-constructed 787?

Sat May 28, 2011 6:22 am

Quoting Starlionblue (Reply 36):
I doubt a 707 or a 727 would be certified today, for example.

No doubt about it...you couldn't certify a 757/767 as-is today.

Tom.
 
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Starlionblue
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RE: Safety Of CFRP-constructed 787?

Sat May 28, 2011 11:47 am

Quoting tdscanuck (Reply 37):

No doubt about it...you couldn't certify a 757/767 as-is today.

OMG they're deathtraps!   
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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Stitch
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RE: Safety Of CFRP-constructed 787?

Sat May 28, 2011 4:35 pm

Quoting soon7x7 (Reply 35):
The entire focus of why major transports are currently transitioning to CF structures has only one goal. To create a fuel efficient machine that can transport revenue PAX further for less money.

That goal has been in place since the dawn of commercial aviation. It's why we make airliners today out of light, thin sheets of aluminum that crumple like a beer can on impact and not heavy, thick stainless steel or titanium that would much better survive impacts.

CFRP looks to be more impact-resistant than aluminum, so in lower-energy events, it could very well improve survivability. But when you auger into the ground or the ocean at many, many hundreds of kilometers an hour...
 
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Starlionblue
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RE: Safety Of CFRP-constructed 787?

Sat May 28, 2011 8:00 pm

Quoting Stitch (Reply 39):
CFRP looks to be more impact-resistant than aluminum, so in lower-energy events, it could very well improve survivability. But when you auger into the ground or the ocean at many, many hundreds of kilometers an hour...

I think at that point the material becomes pretty academic.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
XaraB
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RE: Safety Of CFRP-constructed 787?

Sat May 28, 2011 9:21 pm

Quoting soon7x7 (Reply 29):
A bit sensitive are we?...Believe me, I'm aware of crumple zones...my first car was a 67' Chevy Bel Air wagon. It didn't bend...easily. My Benz does bend,...very easily...$$$
http://www.youtube.com/watch?v=cJrXViFfMGk&feature=related
Have a look at how effective "thicker steel" is compared to crumple zones. Note the differences in cabin collapse... I'll take the "Bendy Benz" any day!

Cheers  
An open mind is not an empty one
 
TSS
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RE: Safety Of CFRP-constructed 787?

Sun May 29, 2011 4:16 am

Quoting XaraB (Reply 41):
http://www.youtube.com/watch?v=cJrXViFfMGk&feature=related
Have a look at how effective "thicker steel" is compared to crumple zones. Note the differences in cabin collapse... I'll take the "Bendy Benz" any day!

Interesting.
Once I got past the idea that someone would purposely trash a '59 Chevrolet that appeared to be in remarkably good shape, I couldn't help but notice the huge puffs of iron oxide dust pouring out of the Bel Air as it crumpled. The main reason there aren't more of '58-'60 Chevrolets left around is that they were much more prone to rust than the '55-'57 models and the '61-'64 models (which used the same basic chassis as the '58-'60 models), so I've got to wonder if a completely rust-free '59 Bel Air might not have fared somewhat better in a similar crash test.
On the other hand, '58-'64 full-size Chevrolets (Impalas, Bel Airs, Delrays, and Biscaynes) used an "X" frame that had no side rails whatsoever, and this particular frame design may have contributed to the Bel Air's poor showing in the offset frontal crash test.
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justloveplanes
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RE: Safety Of CFRP-constructed 787?

Sun May 29, 2011 2:28 pm

Quoting soon7x7 (Reply 35):
Safety used to be the selling point but no more...economy is the marketing buzz word that commands billions ($$$) in orders. Having said that, I feel design has been leaned out, the envelope pushed, thought outside the box....whatever cliche you decide to attach to the process. I'm not confident about hyper automation in the flight domain nor do I feel terribly secure in plastic machines in hostile environments. That's just me,... and a few others that probably don't want to chime in, but I know your out there...g

Safety is a huge selling point in today's airliners. The latest gen airliners (777, 340, 767, 380) are much much safer than your ride to the airport. We take airline safety for granted in fact, a key underlying reason it has grown so much. So you don't see airline safety in ads anymore because high safety is assumed. All the lessons learned from one generation are applied to the next.

Given airliner's safety record compared to other forms of transportation, and their necessity in a global ecomony, it is important that B and A push the efficiency envelope for economic and ecological reasons. I hope Boeing keeps a similar safety record as newer planes.
 
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SEPilot
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RE: Safety Of CFRP-constructed 787?

Sun May 29, 2011 10:23 pm

Quoting justloveplanes (Reply 43):

Safety is a huge selling point in today's airliners.

But the safety that sells is aircraft that don't crash at all. Seeing as how many recent airliners have gone well over a decade before the first one crashes in airline service (this is true of the 757, 767, 777, A330 and A340) and the A380 has not yet crashed, the survivability of the crash is less important than the lack of a crash. And the crashes that were survivable (777, A340 have had crashes with 100% survivability) would have likely had the same 100% survivability had they been CFRP; the crashes that were unsurvivable would have likely had the same result with CFRP. You have to look at scenarios such as UA232, where you had approximately half the passengers survive, to see if CFRP would have made a difference. Frankly, we really won't know until something similar happens to a CFRP plane.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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Starlionblue
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RE: Safety Of CFRP-constructed 787?

Sun May 29, 2011 11:19 pm

Quoting SEPilot (Reply 44):
You have to look at scenarios such as UA232, where you had approximately half the passengers survive, to see if CFRP would have made a difference. Frankly, we really won't know until something similar happens to a CFRP plane.

So basically we should give the Mythbusters a 787, have the fill it with pig carcasses, and take a road trip to Edwards AFB. 
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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SEPilot
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RE: Safety Of CFRP-constructed 787?

Mon May 30, 2011 12:01 am

Quoting Starlionblue (Reply 45):
So basically we should give the Mythbusters a 787, have the fill it with pig carcasses, and take a road trip to Edwards AFB.

Not a bad idea at that.... 
But seriously, no matter what we can theorize about, the question will only be answered when the first survivable crash of a CFRP airliner happens and the investigators are able to compare the results with similar Al airliner crashes. Hopefully this will not happen for a long, long time.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
aklrno
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RE: Safety Of CFRP-constructed 787?

Mon May 30, 2011 12:45 am

Quoting Starlionblue (Reply 45):
So basically we should give the Mythbusters a 787, have the fill it with pig carcasses, and take a road trip to Edwards AFB.

And we could fill some of the fuel tanks with barbeque sauce for a tasty treat after the test. Maybe it is time for dinner.
 
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Starlionblue
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RE: Safety Of CFRP-constructed 787?

Mon May 30, 2011 1:02 am

Quoting aklrno (Reply 47):
And we could fill some of the fuel tanks with barbeque sauce for a tasty treat after the test. Maybe it is time for dinner.

Thanks for that image... Eeeeeewwww.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
JayinKitsap
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RE: Safety Of CFRP-constructed 787?

Mon May 30, 2011 8:26 pm

The OP is basically taking the position that New is Bad, and that the testing that goes into certification means nothing. It also discounts the fact that CFRP has been in use for around 4 decades, with Fiberglass being around 7 decades, another composite called reinforced concrete for about 14 decades, and other composites being in use (straw reinforced mud) for 1,000's of years before metals evolved. Engineers select the best materials for the job being designed based on a wide selection of factors. As a structural engineer of buildings and of fiberglass structures I go thru those choices often - selecting concrete, wood, steel, stainless, AL, plastics, or fiberglass for the components. Often a project will have several.

Modern metal production produces very good materials with remarkably small variation from within a batch or from batch to batch. It generally has unidirectional properties and the classic elastic to yield, plastic past to failure stress strain curve. Fabrication from the metal sheets is not high tech and is the most proven method around aviation. However, welding of AL still has technical challenges. Thin metal has the very nasty sudden compuression buckling mode that has zero warning and propagates rapidly. Fatigue cracking and crack propagation are also huge issues.

Composites have made great inroads in Aviation, the most amazing component to me is the composite engine blades. As a hull skin composites make perfect sense compared to metals. As a new entrant into wing skins issues such as lightning need to be addressed. But they are and will be addressed.

I personally predict that neither Boeing and Airbus will design a metal skin plane again. Using composites will be their way of differentiating from the other manufacturer's. Also, composites have the potential of reducing the unit manufacturing costs with a higher initial investment. However, once invested it will be easier to provide a better product at equal or less cost than the Chinese.

Right now Chinese manufacturing is struggling with the repeatability of their mechanical systems because the quality /tolerance if the parts is not there. How many commercial diesel or car engines are made in China. The Chinese small gas engines and gearboxes are basically unrepairable. That is something they can learn and change but is a major issue. If they cannot be repeatable in metals it is hard to believe that they can have the quality control to master high stress composites.

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