See kids, this is what happens when you prematurely unbag a part, and then post cure not under vacuum. Resin fractures. Which leads to part weakness, and then failure modes.
Also, the Z fibers lifted away from the tooling surface, and returned to their pre-stressed looping.
Fabric: 3Tex carbon/S-Glass 3D, 2 plys.
Resin: Applied Polymeric SC-15, 22hr RT, 2hr 200f cure.
Pretty cool photo! I think I like this type of pic better than the fisished product.
can things be post cured once they are out of the bag and out of the mold? (provided that it is not out too soon and it holds it’s shape on it’s own?)
if freshly moulded things are postcured when out the mould or released from vacuum then generally you will get the fabric printing through and giving a textured lumpy finish and also things can start to deform if not supported by the mould.
Is that the case even it you don’t post cure at extreme temps but rather just middle of the road?
depends on what resin you are using. I have done a fair bit of testing on this as I need to have good machinabilty in a short amount of time. If you let an epoxy/carbon matrix sit for a couple of days and then demould + start postcure at 50deg C then I got quite bad printhrough + lots of little pinholes appearing on what would otherwise be a perfect glossy finish.
Some people even have second duplicate moulds for postcuring so that production ones remain just so.
I found the best way is (if your production mould will take the temp) to let it harden off under vacuum in the mould and (still in mould) stick it in oven + ramp up the postcure temp gradually. We go from about 40 deg to 85 degC for epoxy.
This is where prepreg has a great advantage for us. We can have a component from going in heat press to being machined in about 45 minutes.
holding shape is not the problem, it’s having all the bagging stresses released before it is FULLY hardened.
The best bet is to put the mold under vacuum into the oven (or heat of whatever sorts), then it all stays exactly how it should. Sometimes the resin will even soften when post cured, causing full part deformation.