By Noughtninety - 11/9/2019 1:21:52 PM
Hello all
I have problems with pin holes on every part I try to make I use the same mold high temp epoxy mold made in wet lay post cured to 160 first ply de bulked additionally another three plies of VTC 401 416 g compatible with the 212 285 g curing using both recommended cures . Cure 1:- in at 20 deg 1 min ramp up to 50 - 30 mins dwell at 50 for 1 hour ramp up to 60 10 mins dwell at 60 for 1 hour ramp up to 70 10 mins dwell for 10 hours . part not perfect some pin holes using non perforated release film . Cure 2 . is in at 20 ramp up to 50 30 mins dwell at 50 1 hour then ramp up to 60 10 mins dwell for 1 hour then ramp up to 70 10 mins then dwell for an hour then ramp up to 120 50 mins then dwell for 1 hour . part not good a lot of pin holes all over using no perforated release film . tried so Cure 2 with perforated release film ? and result was still pin holes but 50% less .
Has anyone used the pre preg and found a sweet spot cure ?
I have tried a lot of other cures all different dwell temps and periods to no avail ..
I've also used easy composites xc110 to the recommended cure to no avail either just end up with pin holes
the part is on full vac no leaky bag or anything I even leave breather off the part to allow more pressure onto the carbon .
and the oven I'm using is a very expensive easy composites specifically made oven for this process .
Thank you for your info / help in advance
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By explorecomposites - 11/12/2019 3:26:00 PM
Just a thought, but what is the tool surface finish? I have found that pinholes are way more common with say a 320 grit finish than with a polished finish. Adhesive teflon release works really well too for a low-pinhole surface. Something to do with surface tension I think... not sure of the mechanism.
For oven-cured prepregs, unless it's a special situation, I always use a perforated release film and light breather. Autoclave curing is the only time I'd routinely use a non-perforated release. If you have 4 plies of 400g prepreg, then peel ply shouldn't be an issue bleeding resin. If you can't get light breather, use some 200g dry e-glass as your breather layer. It works great. For thicker stuff where the bleed is heavy, add some infusion mesh over the top of the breather.
And like Warren said, is vacuum really good? Do you drop test the bags before the cook? Also, how thick is the mold?
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