CFRP vs Carbon/Carbon CMC's

Faro · 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

Balerit · 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.

WIederling · 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.

Balerit · Mon Dec 04, 2017 6:14 pm

https://www.youtube.com/watch?v=is1BBilkyUM

PhilBy · 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.

kalvado · 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.

Balerit · Sat Dec 09, 2017 5:32 pm

https://www.youtube.com/watch?v=CRIVPhJpFjM

https://www.youtube.com/watch?v=XEiWwRyq_9E

Faro · 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

WIederling · 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...

C=C !
give 4 , take 4

Nomadd · 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 · 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.

( ex WP:EN )

Techfellow · Mon Apr 23, 2018 12:16 pm

For sake of definition:
CFRP = carbon fiber reinforced plastic. The plastic, considered an organic, is typically epoxy, although bismaleimide and polyimide matrices are also used in some applications. The service temperature for commercial aircraft (10k hours) of these materials is limited to less than 600F (315C) for polyimides, less than 300F (150C) for epoxies. Both of these temperatures are really pushing the limits of thermal oxidation for carbon fiber organic matrix composites. .
CMC = ceramic matrix composites consists of. ceramic fibers in a ceramic matrix. CMCs fall into two classes oxides, consisting of alumina and aluminosilicate, and non-oxides, consisting of carbides, nitrides, and carbon/carbon. Ceramic matrices are considered inorganic.
Oxide CMCs typically use Nextel fiber. The service temperature of oxide CMCs is below 1800F (980C).
Nonoxides typically use silicon carbide fibers. The service temperature of non-oxide CMCs is above 2000F (1090C).
Carbon/carbon composites have carbon fibers in a carbon matrix. These are considered CMCs. Their service temperature is over 2400F (1315C).

CFRP vs Carbon/Carbon CMC's

CFRP vs Carbon/Carbon CMC's

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