Fiber volume fraction for a carbon composite

[bobbywvu]

While doing burn out test for a carbon composite, I found that the carbon fiber is burning along with the resin material. So I was not able to obtain correct fiber volume fraction of my sample. Any suggestions are welcome.
Thanks..

 

[berkshire]

bhyrav (Materials)
If you are using epoxy resin you can sometimes remove the epoxy from the carbon fiber with acetic acid. this may take a while.Miller-stephenson in Danbury Ct., has some commercial strippers for removing epoxy potting compounds from electronic components. These will also work,although they too are slow.
B.E.

 

[bobbywvu]

Thank you very much for your reply, but I am using Vinyl ester resin and I tried it with acetone to dissolve that, and also concluded (basing on literature)that it is very difficult to find a chemical which can completely dissolve the matrix material.
thank you again..

 

[berkshire]

bhyrav (Materials)
Try using methylene cloride.
B.E.

 

[bobbywvu]

Berkshire:
Thank you !! I will try this
bhyrav

 

[Compositepro]

In the aerospace industry the standard method for fiber volumes is acid digestion. A hot mixture of conentrated nitric and sulfuric acid is used. The fibers are the carefully washed and filtered. A test takes several hours. Methylene chloride will not work. It may breakdown the resin to some extent but not enough to be cleanly separated from the fibers.

 

[bobbywvu]

compositepro:
can you explain on what criterion we should select the chemicals for acid digestion?
Thanks

 

[berkshire]

Compositepro (Chemical)
If you are going to use acid digestion with Vinyl Ester resin, surely you are going to have to use concentrations above 50% nitric acid to water and at temperatures close to boiling to have any effect at all on this resin.
B.E.

 

[Compositepro]

See ASTM D 3171. This is somewhat decsribed here:

http://www.tc.faa.gov/its/worldpac/techrpt/ar04-50.pdf

 

[bobbywvu]

Thank you very much lot of useful information about testing

 

[Obsidian]

Another standard acid digestion method is to use conc sulphuric acid ( 98% ) heated to about 160 Deg C . ( You'll need a good fume cabinet ) . Upon reaching this temperature SLOWLY pippette into the mix 10 mls of 100 vols Hydrogen Peroxide ( This is very volatile so take care )until a clear solution is obtained . ( If disolouration is still observed you can re-heat and add more H2O2 ) . The remnants can then be filtered .

In terms of the measurement the more critical aspects are the determination of the volume and density of the original specimen . It is expected that the density of the resin and the fibre are known .