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Faro
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CFRP vs Carbon/Carbon CMC's

Mon Dec 04, 2017 11:42 am

According to the Wiki, the materials science definition of a ceramic material (eg, in a Ceramic Matrix Composite CMC context) is as follows:

A ceramic is an inorganic compound, non-metallic, solid material comprising metal, non-metal or metalloid atoms primarily held in ionic and covalent bonds.


Carbon is therefore considered a ceramic material. What is the difference then, between classic CFRP's and carbon/carbon CMC's?

What type of ceramic material is used in GE's CMC components in the LEAPX and GE9X engines?


Faro
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Balerit
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Re: CFRP vs Carbon/Carbon CMC's

Mon Dec 04, 2017 12:38 pm

Fibre glass is made from glass - trade name Fibre Glas and comes in chopped strand matt or woven cloth form, whereas carbon fibre is made from graphite consisting of mainly carbon atoms. Kevlar is the registered trademark for a para-aramid synthetic fibre. The common thing with all these is that they are bonded or glued together with epoxy or other type of resin. I would guess that the engine components are solid being either cast or 3D printed.
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WIederling
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Re: CFRP vs Carbon/Carbon CMC's

Mon Dec 04, 2017 3:56 pm

Balerit wrote:
I would guess that the engine components are solid being either cast or 3D printed.


Then they would not be composite materials.

IMU the matrix ( that keeps the structural fibers together ) material ( $resin glue ) is replaced by carbon compounds.
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Balerit
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Re: CFRP vs Carbon/Carbon CMC's

Mon Dec 04, 2017 6:14 pm

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PhilBy
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Re: CFRP vs Carbon/Carbon CMC's

Thu Dec 07, 2017 6:01 pm

Carbon is a ceramic. carbon is very strong and tough if crystalline defect can be avoided. Unfortunately manufacturing large flawless crystaline structures is still far from commercially economic. Carbon (and glass) fibres, being very thin reduce the potential for crystaline defects. In the event of a defect in one fibre there re thousands of others that do not have a defect in that location.
CFRP uses a relatively soft elastic matrix which allows for a good load distribution between the fibres in the structure. The matrix adds little to the overall structural strength and therefore CFRP typically has a better strength/weight ratio for most uses.
From an economic view point a composite that can be quickly slapped together in a manufactuary that is by modern standards low-tech is very interesting. Both major manufacturesrs are still investigating out of autoclave processes to speed up production and reduce costs.
A CMC aircraft would be very structurally effficient, almost impossible to manufacture and priced beyond the range of anyone outside the USA military. Just the cost (time, drill bits) of drilling the required bolt holes in a cmc structure would probably kill the business case.
 
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Re: CFRP vs Carbon/Carbon CMC's

Thu Dec 07, 2017 6:20 pm

I wouldn't call either graphite or diamond "ceramic"
Ceramic for me is something with strong polar bonds, creating high bandgap and chemical resistance - mostly oxide or nitride.
 
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Balerit
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Re: CFRP vs Carbon/Carbon CMC's

Sat Dec 09, 2017 5:32 pm

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Faro
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Re: CFRP vs Carbon/Carbon CMC's

Mon Dec 11, 2017 10:25 am

kalvado wrote:
I wouldn't call either graphite or diamond "ceramic"
Ceramic for me is something with strong polar bonds, creating high bandgap and chemical resistance - mostly oxide or nitride.



FWIW, the Wiki also quotes carbon as being a ceramic...


Faro
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Re: CFRP vs Carbon/Carbon CMC's

Mon Dec 11, 2017 6:15 pm

Faro wrote:
kalvado wrote:
I wouldn't call either graphite or diamond "ceramic"
Ceramic for me is something with strong polar bonds, creating high bandgap and chemical resistance - mostly oxide or nitride.


FWIW, the Wiki also quotes carbon as being a ceramic...


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Re: CFRP vs Carbon/Carbon CMC's

Tue Dec 12, 2017 4:17 pm

Faro wrote:
kalvado wrote:
I wouldn't call either graphite or diamond "ceramic"
Ceramic for me is something with strong polar bonds, creating high bandgap and chemical resistance - mostly oxide or nitride.



FWIW, the Wiki also quotes carbon as being a ceramic...


Faro

That sounds contradictory since the Wiki definition of ceramic is "inorganic", and the broadest definition of inorganic is non carbon containg.
 
WIederling
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Re: CFRP vs Carbon/Carbon CMC's

Tue Dec 12, 2017 5:55 pm

Nomadd wrote:
Faro wrote:
kalvado wrote:
I wouldn't call either graphite or diamond "ceramic"
Ceramic for me is something with strong polar bonds, creating high bandgap and chemical resistance - mostly oxide or nitride.



FWIW, the Wiki also quotes carbon as being a ceramic...


Faro

That sounds contradictory since the Wiki definition of ceramic is "inorganic", and the broadest definition of inorganic is non carbon containg.


A chemical compound is termed inorganic if it fulfills one or more of the following criteria:
* There is an absence of carbon in its composition
* It is of a non-biologic origin
* It cannot be found or incorporated into a living organism
There is no clear or universally agreed-upon distinction between organic and inorganic compounds.

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