Talk Composites - The Forum for Advanced Composites

White spots inside of my Carbon Fiber Epoxy Laminate

http://www.talkcomposites.com/Topic24854.aspx

By tsombnik - 1/8/2018 11:59:55 AM

Hello friends,

i am currently working on a project where we are manufacturing CFRP Parts with vacuum assisted RTM process. We are using infusion resin with infusion hardener (HP Textiles (HP-HE3000RI-30) / HP Textiles (HP-HTE300RI-9)) and Semiperm Monofilm R&G Release Agent. We are experiencing weird white spots inside of the part after curing of the resin and arent able to fix them. The wierd thing is, that we have these white spots very concentrated at a few positions of the part. The rest of the resin inside the resin pot is clear!  What could be the problem? This is how the process looks like:

1) Inserting preform into the tool
2) Closing of the tool
3) Vacuuming of the tool
4) Injecting of the resin with 0,7 bar injection pressure
5) Wait 2 days until resin is cured
6) Open the tool

I have added a picture inside of my post. I hope you can help.

Thank you very much for your potential help,

All the best, Nik
By fibernoob - 1/9/2018 1:43:25 PM

 
tsombnik - 1/9/2018 7:21:08 AM
 
fibernoob - 1/8/2018 11:58:06 PM
Im not sure its your case... but  I have had similar problems when I used too much (wax based) release agent and did not polish it into the mold.   




Hello fibernoob,
we also used wax based release agent in the area of the sealing cord, so that we can use it again if resin reaches the sealing areas of the tool. So yeah, im pretty sure this can be the reason. We are going to clean the tool again and wont use the wax release agent anymore.
If somebody has another idea though, please tell me BigGrin Maybe it can help.

Thank you for your help!

Nik


After getting some information, i discovered that  wax based release agent has to be applied and thoroughly polished and left for some time for the solvents to evaporate and leave just a thin film of wax (invisible chemical barrier).   Remember that your part will replicate the texture of your mold... if its smooth and well polished (shiny surface) with release agent it will come out perfect.

In my case, I thought that the more release agent i would cover the part with  ... the easier it would demold!   That was my mistake.

The part then showed similar white residues on many places.   Check if those white spots have a similar greasy texture to make sure its release agent.

You can use Water Based release agent (PVA) but it is not as easy to polish or spread uniformly.

If the problem is not release agent related, it can be what the other comments are suggesting.   There are valid points being made... Humidity , Resin Ratios etc.  

Good Luck !