Curing in sun?

Talk Composites - The Forum for Advanced Composites

Back

Curing in sun?

Author	Message
Roo2	Roo2 posted 8 Years Ago HOT Topic Details
Group: Forum Members Posts: 8, Visits: 31	Hi there, I messed up a couple of small parts yesterday by trying to finish curing in the morning sun. I made some fibreglass angles using an aluminium angle extrusion as a mold. I coated the aluminium with a smear of pva release agent. Then wrapped a layer of peel ply using a light dusting of 3M77. Then 2 layers of fiberglass and a final layer of peel ply all held with a bit of 3M77. I infused with some low viscosity, slow (4hr) set epoxy. Everything looked excellent the following morning, about 12 hours after the infusion and I started to de-bag. I discovered the resin was still a bit sticky so I decided to put the lot out in the sun for a few hours.. I came back about 2 hours later to discover the laminate stack had "inflated" off the aluminium extrusion mold about 3mm and formed curved cross sections rather than nice square angles.. Scrap.. It's autumn here in Brisbane, Australia and not hot. The sun doesn't seem fierce but maybe.. Any suggestions what happened? It seems like the laminate stack has been pneumatically inflated off the mold by some form of gas coming from the curing resin, acelerated by the sun.. Trying to add a photo but I don't seem to be allowed right now..
	Reply Like 3
Roo2	Roo2 posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 8, Visits: 31	I'm not being allowed to add a photo as I've already exceeded my available space..
	Reply Like 2
Hanaldo	Hanaldo posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	It's not inflation or anything pneumatic; it's shrinkage of the resin. By demoulding before the resin was filled cured, you had nothing to keep the laminate held in shape, and so the resin shrinkage caused it to curl up. The direction of the curl is dictated by the geometry of the shape, as well as the fibre orientation. Certainly the sun would have made it worse, as the higher temperature would have increased the shrinkage.
	Reply Like 3