Carbon fiber sheet, perfect finish on both sides


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f1rob
f1rob
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Might have some here mate what exact thickness are you looking for an what size ???
scottracing
scottracing
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was that with pre preg? I was looking for someone to make me some 2 ply sheet or just an offcut to make a new visor mount for my momo helmet, as I left all my glass sheets in germany and theres nothing thin enough at work Sad
morepower
morepower
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It would be mostly down to the cure cycle you are using. Here I had to make a couple of single layer sheets. 



This was just two sheets of glass with release film wrapped round it and then breather. The release was to just stop the excess resin being pulled into the breather. 
ChrisR
ChrisR
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There's your problem, always apply to a cloth first then wipe onto the mould
peter_lisica
peter_lisica
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Thanks for the tips




Yes i do use gloves, but i don't change the cloth for each coat. And i'm pretty sure i applied a too heavy coat as i just sprinkle it on the glass and then wipe down.
Hanaldo
Hanaldo
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I found that is more of an application error. There's 3 main things that cause it:

1: Don't apply too heavy a coat. If you apply too much, the liquid will separate and leave streaks. 

2: Do you wear gloves when you apply it? If not, the solvent in the Frekote dissolves the oils on your hands and deposits them on your tool surface leaving smears.

3: Similar problem if you don't use a new cloth to apply each coat, are you using the same cloth or getting a new one for every coat you apply? If you use the same cloth, you end up with the Frekote polymers drying on the cloth and then you apply more and the solvent partially dissolves the polymers again leaving a greasy residue on your tool surface. 

The solution is to wear gloves, and use a new cloth for each coat. I like to cut my application wipes into 5 pieces so I don't go through a heap of them. Also make sure you clean the surface really well with solvent (preferably NOT acetone) to ensure any grease or residues that are already there don't get smeared around by the Frekote. Do these things and the Frekote will barely leave any residue at all, certainly not anything that transfers. 
peter_lisica
peter_lisica
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Hy




now that i have a pin hole free surface i have another question.




Although the surface is smooth there are still some stripes visible from the release agent i think. I am using a frekote 770-nc.

Is there a way to get ride of this stripes on carbon fibre. And how/can I get rid of this problem when applying the release agent. I have tried polishing it with a smooth cloth by hand after the release agent has dried, but it seems that is not enough.




Thanks
peter_lisica
peter_lisica
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Thanks Rob,




I taped the edges, and straight to 120C at 3 bar and the result is outstanding Smile

no pinholes, really perfect glossy finish on both sides.
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f1rob
f1rob
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Well looking at the data sheet its a 42% resin material an a fairly standard cure (120,2 dag a minute ramp)

For a single ply you wouldn't need a dwell so straight to 120

but on glass you should be ok with 30psi to get the Finnish but still tape the edges off
peter_lisica
peter_lisica
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Hy the carbon fiber si twill 200g/m2, and the technical data sheet of the epoxy is here http://www.delta-tech.it/pdf/STE%20DT120-6.pdf




What i found is that nearer the edges there are less and less pinholes, to about 2cm from the edge there are no pinholes left.

The main focus is that we get rid of this pinholes on both sides and is not important structuraly.




And another thing that i found out is when i put the glass panel on just one side, the surface was perfect and pinhole free.

How would you recomend the autoclau cycle (pressure and temperatures) to give the best chance of getting what i want.

And also i am wondering what is causing the pinholes. Is it gas forming in the epoxy that can't escape, or is it epoxy bleeding out.




F1rob




Yes the carbon fiber sheet is the same size as the glass panels but i didn't flash tape around so I Will try that also, if the problem is resin bleed.




Regards
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