Discussion in 'Composites' started by undean, Oct 19, 2019.
Oh they'll cure as they exotherm alright!
Just a random thought....but it seems perhaps higher strength and higher Tg come with a post cure heat treatment......Perhaps the key phrase is "post cure"
Not that I know of, not reliably. My experience with curing 2080 under heat is that it sometimes cures in the vacuum taps before it cures in the laminate. The result is vacuum loss and an expensive junked part. Now we're very careful about how we filter the taps and how we apply the heat.
That is the general relationship. But don't let yourself be intimidated; we made a perfectly good post-cure oven with stuff from the hardware store and Dollar General. We do a pre-post-cure of the individual parts in the molds to 100 F with heating blankets and quilts from the thrift store, that gets things tough enough to demold. Then once everything is assembled and bonded together, we ramp them in the hot box up to about 170 for four hours, hold there for another three or four, then de-energize the heating elements and let it ramp down overnight. Coupons are showing this is perfectly fine for the properties we're looking for.
Tub_postcure_4 by Voidhawk9 posted Oct 24, 2019 at 4:32 PM
Simple post-curing my canard fuselage. Simple wooden frame that fits around my workbench and a tarp over top. Add heat. You can see the electronic controller which enables me to set the desired temperature. There is another heater at the other end inside (since I was going to 70c on this occasion) and another fan to circulate.
Post-cure requirements and properties vary with the system used, of course. I'm using a system manufactured here in NZ, since shipping epoxies half-way around the world isn't very economical.
One could make the argument that you can post bake your epoxy by merely letting the aircraft sit in the hot sun for x hrs/days.
the sun will bring the core temperature up to over 150-170 degrees very easily.
Post bake cure problems solved.
That often kind of works. But the ramp rate and temperature distribution are hard to control.
You can always do it like this.
Merely using the insulation board as a wall and using small fans to pump air in/out in order to control the temperature ramp up and ramp down. A simple temperature controller is used to handle this.
Use a space heater to get the heat source. You can be trick and use vacuum on the parts at the same time if desired
Ramp rate was controlled manually in steps. Distribution was managed with lots of air circulation (big fan inside blowing air - that's the bump you can see under the tarp).
Just so. I was responding to a different post, perhaps one hidden from your default view.
Ah, so it was.
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