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kitplane01
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GFRP vs CFRP

Wed Apr 04, 2018 3:13 am

lightsaber wrote:
Next generation:
1. GFRP wings (not CFRP).


Can someone comment on how much better GFRP is as an aircraft construction material than CFRP? Wikipedia does not help much.
 
trijetsonly
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Re: GFRP vs CFRP

Wed Apr 04, 2018 2:13 pm

The first advantage coming to my mind is the sustainability and isolation to eletrical loads / lightning strikes / statics.
I have no idea about material strength and weight.
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AIRWALK
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Re: GFRP vs CFRP

Wed Apr 04, 2018 7:49 pm

I do believe GFRP is more ductile which allows more elastic deformation as compared to CFRP
I'm sure this thread will take off soon
 
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Balerit
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Re: GFRP vs CFRP

Fri Apr 06, 2018 8:10 am

The only thing about fibre glas construction is it is cheaper and less hazardous with regards to fumes during the manufacturing process otherwise carbon outperforms it in every other aspect.
Licensed Aircraft Maintenance Engineer (retired).
 
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Slug71
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Re: GFRP vs CFRP

Fri Apr 06, 2018 2:06 pm

What Balerit said.
But try reading up on FMLs(Fiber Metal Laminates), ie GLARE. I know its slightly different since it's using metals instead of Polymer. But I assume its reasons are similar. Some big improvements are being made to the manufacturing process of C(carbon)FMLs currently. I think carbon will pretty much replace glass going forward. Especially since advancements in carbon like Carbon Nanotubes are being made too. Theres a few good links in the "2025ish A380-900NEO" thread here. I think theres a good chance we'll see aircraft using both CFMLs and CFRP in the future.
 
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lightsaber
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Re: GFRP vs CFRP

Sat Apr 07, 2018 4:32 pm

The main advantage of Graphite Fiber (the new stuff) is damage tolerance.
A small amount better Young's modulus match due to binder changes.

New binding plastics too. The weight of CFRP builds is due to:
1. Protective layer of epoxy to minimize damage to the underlying fibers
2. Added (multiple) layers for damage tolerance.
3. Mis-match in fiber/polymer Young's modulus limits deflection (it is good, but not outstanding).

Slug71 wrote:
What Balerit said.
But try reading up on FMLs(Fiber Metal Laminates), ie GLARE. I know its slightly different since it's using metals instead of Polymer. But I assume its reasons are similar. Some big improvements are being made to the manufacturing process of C(carbon)FMLs currently. I think carbon will pretty much replace glass going forward. Especially since advancements in carbon like Carbon Nanotubes are being made too. Theres a few good links in the "2025ish A380-900NEO" thread here. I think theres a good chance we'll see aircraft using both CFMLs and CFRP in the future.

The CFRP/GLARE being used in airframes is old school. Over 15+ year old materials.

It isn't just carbon nanotubes. There are other things that can be done with carbon. :)

Balerit wrote:
The only thing about fibre glas construction is it is cheaper and less hazardous with regards to fumes during the manufacturing process otherwise carbon outperforms it in every other aspect.

Not glass, Graphite. It is a little more than going back 20+ years in technology. The old obsolete acronym has been recycled. Partially to obscure the research. :)

I believe it will save a few tons of weight.

Lightsaber
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Balerit
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Re: GFRP vs CFRP

Sat Apr 07, 2018 7:13 pm

We still use GFRP to mean glass fibre reinforcing and CFRP as carbon fibre reinforcing - also known as graphite. Kevlar is the trade name for a third reinforcing plastic that is known as a para-aramid synthetic fiber. Glare is a sandwich construction made up of sheets of fibre glass and aluminium bonded together and seems to be making a comeback at Airbus.

https://www.compositesworld.com/blog/post/the-resurgence-of-glare
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lightsaber
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Re: GFRP vs CFRP

Sat Apr 07, 2018 8:35 pm

Balerit wrote:
We still use GFRP to mean glass fibre reinforcing and CFRP as carbon fibre reinforcing - also known as graphite. Kevlar is the trade name for a third reinforcing plastic that is known as a para-aramid synthetic fiber. Glare is a sandwich construction made up of sheets of fibre glass and aluminium bonded together and seems to be making a comeback at Airbus.

https://www.compositesworld.com/blog/post/the-resurgence-of-glare

Fair enough, but not what I was referring to in the post the OP noted.
I used the terms I'm used to. Cest la vie. I was not referring to prior generation carbon fiber as there are known issues with Young's modulus compatibility that have been found over the decades.

What matters is there is another generation of reinforced plastic coming down the pipeline for wings, woven bodies, and panels. On new structures, it saves weights. In some cases, allows better geometry which saves weight.

Please put on your stress engineer and material scientists hat and think of what you would improve in CFRP to make a next generation airliner cheaper to manufacture and lighter. What would you change? If you have made aerospace parts you are well aware of how much weight ends up in the final structure to ensure long life via damage and fatigue resistance. I'm talking everything from making the structure more rigid so that the Young's modulus imbalance doesn't matter or with the addition of sacrificial layers and that heavy epoxy coating the outside parts receive.

Old materials will stay in use. Yea! Although 3-D printing will really shift what is used. In particular, it is now cheaper to print Titanium than make the old way parts out of Aluminum. :)

What I was specifically discussing in another thread was how new GFRP (Graphite) materials will save weight over the current CFRP wings. And yes, I'm well aware of all the titanium and even aluminum inside a CFRP wing.

I personally believe the next generation of wings will have an example woven instead of put together in piece parts. This will require far more automated assembly and thus will only be viable for a mass produced wing (such as the MoM/797). We're at the point we can build much more Net shape assemblies.

Some of this will come from the 'textile reinforcement' concepts of the woven mats. But why not weave from scratch? In particular as I'm a fan of more organic structures. :cloudnine: Alas, we aren't ready for that yet...

This is just one bullet for a long list I wrote off the top of my head how next generation aircraft will continue to advance and burn less fuel.

Next generation materials have been going into prototypes for years. When will we get to see them in commercial service?
Lightsaber
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Balerit
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Re: GFRP vs CFRP

Sun Apr 08, 2018 10:08 am

Interesting thoughts Lightsaber, unfortunately I'm retired now so I not up to scratch on the very latest techniques but the Russians have some interesting manufacturing methods as well. Another thought comes to mind and that is the yacht building industry seems to be the leaders in this tech.
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lightsaber
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Re: GFRP vs CFRP

Sun Apr 08, 2018 5:16 pm

Balerit wrote:
Interesting thoughts Lightsaber, unfortunately I'm retired now so I not up to scratch on the very latest techniques but the Russians have some interesting manufacturing methods as well. Another thought comes to mind and that is the yacht building industry seems to be the leaders in this tech.

Yes, the Russians have done much for cold cured composites. They remain the leader in Titanium welding and some other titanium processes.

There is much going on to move the technology forward and I certainly only have insight into a few possibilities. Some reduce manufacturing costs more than anything else and some reduce weight.

What I know is little has been done with 15+ years of R&D. Somehow tens of millions of research hasn't been implemented other than in prototypes (I included the MC-21, until certified, in this category). Now, the first of the new technology in composites will see operation in the MC-21.

Otherwise, there have been better aluminums, titaniums, and of course 3-D printing. Mostly to reduce cost.

I'm more excited when cost and weight drop...
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JayinKitsap
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Re: GFRP vs CFRP

Tue Apr 17, 2018 1:46 am

On several buildings I am involved in are using panels of 26 ga steel (or aluminum) sandwiching a foam core. They work great and are quite lightweight. Glare or a composite skin on a light core insulation would have amazing performance, provided the bond of the skin to the core isn't weak. Thermal expansion can play havoc with that bond.
 
WIederling
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Re: GFRP vs CFRP

Tue Apr 17, 2018 9:28 am

JayinKitsap wrote:
On several buildings I am involved in are using panels of 26 ga steel (or aluminum) sandwiching a foam core. They work great and are quite lightweight. Glare or a composite skin on a light core insulation would have amazing performance, provided the bond of the skin to the core isn't weak. Thermal expansion can play havoc with that bond.



quite some time ago I worked with this stuff:
https://www.metawell.com/en/
(Aluminium sandwich panels in a "corrugated cardboard" style )
Murphy is an optimist
 
JayinKitsap
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Re: GFRP vs CFRP

Tue Apr 17, 2018 6:15 pm

WIederling wrote:
JayinKitsap wrote:
On several buildings I am involved in are using panels of 26 ga steel (or aluminum) sandwiching a foam core. They work great and are quite lightweight. Glare or a composite skin on a light core insulation would have amazing performance, provided the bond of the skin to the core isn't weak. Thermal expansion can play havoc with that bond.



quite some time ago I worked with this stuff:
https://www.metawell.com/en/
(Aluminium sandwich panels in a "corrugated cardboard" style )


lots of the plate air-to-air heat exchangers use a flat sheet, a corrugated sheet, flat sheet, corrugated sheet the other direction. to assemble the exchanger. Incoming air passes thru the chambers made by the corrugated sheet, outgoing air used the path 90 degrees apart.
 
flipdewaf
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Re: GFRP vs CFRP

Tue Apr 17, 2018 9:02 pm

JayinKitsap wrote:
On several buildings I am involved in are using panels of 26 ga steel (or aluminum) sandwiching a foam core. They work great and are quite lightweight. Glare or a composite skin on a light core insulation would have amazing performance, provided the bond of the skin to the core isn't weak. Thermal expansion can play havoc with that bond.

Using a sandwich construction is pretty common on aircraft panels already. My guess is you are using PIR panels, they are very common in modern construction as they go up quick. I work I the food industry and have them made with special coatings. As a slight aside I once designed a light weight modular services system so that we could both insulate pipe work and have a light weight cladding system that also supported the pipes whilst being hung from a ceiling not really designed for supporting services ( less legs is good for food factories. Who knew my aerospace degree would be useful for making fries?

Fred


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CowAnon
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Re: GFRP vs CFRP

Thu Apr 19, 2018 8:07 pm

lightsaber wrote:
What matters is there is another generation of reinforced plastic coming down the pipeline for wings, woven bodies, and panels. On new structures, it saves weights. In some cases, allows better geometry which saves weight.

Please put on your stress engineer and material scientists hat and think of what you would improve in CFRP to make a next generation airliner cheaper to manufacture and lighter. What would you change? If you have made aerospace parts you are well aware of how much weight ends up in the final structure to ensure long life via damage and fatigue resistance. I'm talking everything from making the structure more rigid so that the Young's modulus imbalance doesn't matter or with the addition of sacrificial layers and that heavy epoxy coating the outside parts receive.

Thanks for explaining.

I was reading a study from 2013 about shielding requirements for a composite fuselage using open rotor engines, so the subject of material damage resistance is of interest to me (and sadly somewhat topical, considering the Southwest 1380 fatality). Would you consider the following composite setup to be first- or second-generation carbon?

'Weight Assessment for Fuselage Shielding on Aircraft With Open-Rotor Engines and Composite Blade Loss' (http://www.tc.faa.gov/its/worldpac/techrpt/tc13-34.pdf) wrote:
Since new open-rotor designs will likely use composite fan blades and airframes, composite materials were utilized for this study. A triaxially-braided composite of TORAYCA T700S fibers and CYCOM PR520 toughened resin was selected. The braid architecture was composed of 24 k tows in the 0deg direction and 12 k tows in the +/- 60deg directions with the same fiber volume in each direction so that the in-plane stiffness properties were quasi-isotropic. This particular material and fiber architecture was selected for several reasons. First, due to the quasi-isotropic properties, each layer in the composite is identical, and delamination due to inter-ply property mismatch is minimized, resulting in good impact properties. Second, from a manufacturing point of view, this material is both practical and affordable. Lastly, considerable mechanical property and impact test data, as well as analytical material modeling results are available for this material (Refs. 2 to 8). The same braided composite system was used for both the notional blade and shielding structures. This material may not be optimal for a composite blade design, but its relatively high toughness provides for a conservative estimate of shielding requirements. Because of the test verification available for the material modeling, there is a relatively higher level of confidence in the analytical results than is typical for conceptual studies.

I have a mixed opinion about this particular material's performance. The structural requirement quoted just before the summary (page 27) lists a normal minimum thickness of 0.2 inches (5.1 mm), which seems unimpressive compared to the fuselage thickness graph shown at https://leehamnews.com/2015/04/02/bjorns-corner-lighter-fuselages-practical-considerations/, where the thickness for aluminum fuselage can be as low as 1.6 mm. However, the study concludes the composite shield thickness needs to be 0.5 inches (12.7 mm) to prevent blade penetration, with a total shield weight of 236 to 428 pounds. I don't know how that shield thickness amount compares with aluminum, but the shield weight penalty strikes me as reasonally small.
 
CowAnon
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Re: GFRP vs CFRP

Sun May 13, 2018 8:30 am

Here's another interesting carbon-based material - resin-free graphite fiber.
Scientists make strong, super-tough carbon sheets at low temperature (https://phys.org/news/2018-05-scientist ... heets.html) wrote:
"In contrast, our process can use graphite that is cheaply dug from the ground and processed at temperatures below 45 degrees Celsius (113 degrees Fahrenheit)," said Dr. Qunfeng Cheng, professor of chemistry at Beihang University and a corresponding author. "The strengths of these sheets in all in-plane directions match that of plied carbon fiber composites, and they can absorb much higher mechanical energy before failing than carbon fiber composites."
 
AIRWALK
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Re: GFRP vs CFRP

Sun May 13, 2018 1:11 pm

lightsaber wrote:
Balerit wrote:
Interesting thoughts Lightsaber, unfortunately I'm retired now so I not up to scratch on the very latest techniques but the Russians have some interesting manufacturing methods as well. Another thought comes to mind and that is the yacht building industry seems to be the leaders in this tech.

Yes, the Russians have done much for cold cured composites. They remain the leader in Titanium welding and some other titanium processes.


Which is interesting considering the MiG-25 used Steel instead of Titanium because they were having difficulty working with it back then! While the SR-71 was mostly Titanium, actually acquired from the USSR.
I'm sure this thread will take off soon
 
WIederling
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Re: GFRP vs CFRP

Sun May 13, 2018 2:29 pm

AIRWALK wrote:
Which is interesting considering the MiG-25 used Steel instead of Titanium because they were having difficulty working with it back then! While the SR-71 was mostly Titanium, actually acquired from the USSR.


It'd be interesting to see the cost per frame differences between MIG-25 and SR-71. ( 5 to 1 ? or even worse? )

cast steel and Al engine blocks had a trade off race ( for a while?) : refinements in cast steel tech allowed finer structures, thinner walls than Al. result : engine block weights were competitive.

Same you see with other up front "duh, simple" technology decisions: all said and done and having solved all the design requirements that new fangled "super material" may come out as just minimally better or even worse.
Murphy is an optimist

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