[AR] Re: How to make carbon-carbon composites?

  • From: William Claybaugh <wclaybaugh2@xxxxxxxxx>
  • To: "arocket@xxxxxxxxxxxxx" <arocket@xxxxxxxxxxxxx>
  • Date: Sun, 6 Dec 2015 10:25:17 -0500

See below:

On Sunday, December 6, 2015, Oliver Arend <dmarc-noreply@xxxxxxxxxxxxx>
wrote:

After some recent discussions about nozzle materials and thinking back to
a class I had in university, I was wondering how to make carbon-carbon
composites, and whether this is feasible for amateurs/hobbyists.

From what I understand (having read the Wikipedia article ;-), first a
carbon fiber reinforced part is made in the classic way.
Then the part is pyrolyzed, i. e. heated in the absence of oxygen such
that the matrix decomposes and the volatile parts evaporate to leave a pure
carbon matrix.
Since the matrix is now very porous, a gas like acetylene has to be passed
through the part so the pores will be filled with carbon.

So I have a couple of questions:
1. Which resin can be used to manufacture the original CFRP part? Epoxy?
Phenolic? Anything?


Typically highly proprietary formulations that are very fluid but have a
high final carbon content.


2. Is there really the need for additional "carbonization" after pyrolysis
if I want to use it as a combustion chamber or a nozzle?


Yes, 4 to 12 cycles depending on the details, otherwise the porosity leads
to structural failure.


3. Are there any other big obstacles I haven't thought of?


Nozzles really need 3D stitching to be full strength in all dimensions.


Pyrolysis shouldn't be too hard using e. g. a steel container and a CO2
atmosphere at maybe 1000 °C?


Maybe; gas phase systems--which get higher final density--typically use a
high carbon content gas. CO2 is going to generate O or O2 which will
destroy the carbon you are trying to deposit. Vacuum might be better for a
liquid phase system.

Bill


Oliver


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