By Carbon Tuner - 1/11/2012 12:29:08 AM
Hey Guys,
First of I want to say I love what you guys are doing here.
I know the power of forums and am extied to be apart of talk composites! Ive looked around for other forums like this but theres nothing good out there. Also, all those videos and explanation on the websites enspired me to get started in making my own parts.
Anyhow I have made my part a few times now. First few pieces werent so bad but not perfect, which is my goal. After tackling getting everything to fit and form to the mold I still keep finding small inholes across the surface of the part...
At this point I am stuck. Could it be the surface of the mold? Seems to keep hapening so I assume I am doing something incorectly.
Any help would be appreciated,
Donnie
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By Greybridge - 10/24/2019 2:39:11 PM
+x+x+xHi, I have been trying to make Carbon Fiber sheets using resin infusion process. I have given 9 tries till date and have not able to eliminate pinholes. Glass has been used as the mold surface. I use wax and PVA as release agents, have also tried 2 Mil MYLAR sheet as releasing agent, but has not been able to produce single sheet with out pinholes. Size of sheet tried 20mm X 15mm. Mesh area of 25mm X 20mm. Resin Mixture 130 Grams for infusion. Fiber cloth 200 GSM Plain 6 Layers. Resin has been completely Degassed before use. Vacuum Drop test is conducted and have verified full vacuum of -1 bar. I have attached a sample photo can you please let me know where i am going wrong in the procedure Thank you  So the Flow Media is longer than the plate you are making if i understand correctly? Cut the flow media always 2cm or so shorter than the fabric to make sure the resin has to pass through it and can't skim across. Then use a strip of peel ply at the end to pull the vacuum from. We just had this a month ago with someone else. I'm sure you can find that thread somewhere Hi Lester Populaire, Thanks for the reply, When you say flow media you mean the Mesh we apply over peel ply correct. So the mesh should always be lesser than fabric area correct? 
I think what lester meant (and this is how I set up) is hang your flow media and peel ply off the inlet side edge of the part but leave them both short of the vent side (and left and right) edge of the fabric so the incoming resin has to infuse down thru the last 2cm. Having said that, pin holes like you described, in my experience, are the the result of air infiltration during your cure. Trapped air as a result of poor flow management leads to discreet pockets or patches of dry fabric, not systemic pin holes. Does your flow media have little bubbles trapped in it when you come back after the cure? If so, that's air infiltration from a micro leak in your film or bag. It pushes in thru the flow media and down through the part, leaving pinholes everywhere(not to mention scrapping your part). If there's no bubbles in the media, it's possible your leaving it to cure under too high a vacuum. The resin effectively boils itself to swiss cheese as it cures and that can look like pin holes but there's generally a bunch of white frothy residue everywhere, and im not seeing that in the photo. You want to pull resin under full vac but drop it down below the vapor point of your resin before crimping off your lines.
Good luck.
P
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