Trying to switch to prepreg

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#1

Is it possible to use pre-preg in molds that were created for infusion? None of my molds were post cured, and none were created with high temp resins. I use epoxy for 99% of molds. I am more or less trying to see if I would actually have to go back and re-create all of my molds, and post cure them, if I wanted to make the change to pre-preg.

I think Gurit sells a low temp OOA pre-preg, but I think even that product requires a 150degree F cure cycle. I know I could go back and find the heat deflection temps for the epoxy resin and epoxy putties that I use in mold design, but I am sure that 150 degrees would be pushing the limits…

Has anyone ever used normal room temp epoxy molds in a (relatively) low temp pre-preg cure cycle?

#2

What resin system did you use? Most important is the Tg of the mould. Your curing temp cannot exceed this. There are prepreg systems that cure pretty low. Cyctec has one that is 122F. If the mould is fiberglass, it will be a pig to heat up compared to carbon. You will need to account for the temperature offset and ramp rate from this. Lastly is CTE; though if you’re curing at a lower temp its less of a concern. If your tooling and part CTE is different it can cause many issues, and is more noticeable as you get hotter in temperatures. Ideally you would carbon mould for carbon parts

#3

It should be OK… I use high temp polyester moulds for much of my work… Not ideal but has worked for me so far.

I would make a master and keep it to one side to make other moulds with if you do have issues but if it is an epoxy mould you should be OK… SHD have DF212 which cures at 75 degrees C and you can use VTF261 from Cytec too… Both are good Out of autoclave pre-pregs… You will have to test and work out a cure schedule which includes some dwell time as you ramp up so you may go to 40 degrees or 60 degrees etc and let it sit there for an hour or two before ramping up to its final cure temp…