Talk Composites - The Forum for Advanced Composites

Breach unit seal

http://www.talkcomposites.com/Topic19204.aspx

By MarkMK - 9/15/2015 7:54:32 AM

Have run my first few parts using OOA material (EC's own) and, whilst I've got the last couple to come out with only minor pinholing I'm still aiming for a pinhole-free finish as I don't have the facility to finish with clearcoat, although smaller parts I can coat with epoxy and flat.

I'm pretty consistent with getting fully sealed bags with infusion now without need to chase leaks, but finding envelope bagging parts more problematic when, in theory, there should be less to go amiss, so to speak. I'm concerned that my problems may be arising at the breach unit, although I've carefully installed the hosetails using PTFE tape and I'm careful to make sure the through- bag element is screwed down tightly whilst avoiding wrinkles in the bag. I use the larger diameter barb connectors to get a tight fit on the silicone hose too.Cure cycle is a consistent 100° for 8 hours  with temps monitored on the parts with thermocouples and an external thermometer. 

My question is: would any minor leak occuring in this area affect the final part finish if the bag itself was airtight, seeing as it is 'downstream'. Pump is left on during cure with no audible indication from it that there's any air ingress when running, but when left for a few hours during drop tests I've heard a slight tone change for a few seconds when opening the breach unit ball valve. I'm even starting to question the quality of the valve itself. I've also considered curing without the pump, but is a pinhole-free finish realistic to expect even with a totally sealed bag and are there volatiles in the material that really need to be evacuated during cure?

Thanks 

Mark
By MarkMK - 9/15/2015 11:29:31 PM

Thanks for confirming Chris

Thanks for that Hanaldo, I also recall Paul from EC saying that working the surface layer too much, in particular, can cause pinholing so I'll be mindful of that.

 I was laying-up a new mould today with quite a few curves to negotiate and found myself having to re-position a few times, so might not get the best finish, but hopefully a bit of finessing of the cutting template will help make the next part much better. Good to know that the promise of pinhole free parts isn't just a myth, so I'll keep at it.