Talk Composites - The Forum for Advanced Composites

First attempt at Vacuum Bagging

http://www.talkcomposites.com/Topic31071.aspx

By Crusader - 11/21/2018 8:01:21 PM

Had a go at vacuum bagging at the weekend. I've had all the equipment (off Easy Composites of course) for six months and made the mold 3 months ago and at last got round to it.
I'm making a carbon fibre bumper for a 1960's car (Hillman Imp), took a mold off a good steel one. Unfortunately the bumper actually wraps back on itself at the ends so it meant either a two or three piece mold. I went for a 3 piece so I could make quarter bumpers if i want. I added approx 30mm around the outside of the bumper .
 I used easy-lease release agent, six coats + 1 one hour before molding. GC50 epoxy compatible gel coat brushed in followed by 1 layer of carbon cloth, one layer of class cloth and then 1 layer of carbon. I added a strips of carbon tape in the area of the mounting bolts.
  The process went quite well, but I had a few problems when i came to release. One side came out well with a little bit gel coat stuck in the mold, the other side left most of the gelcoat attached to the mold. The bumper seemed quite dry with the layers delaminating as I removed it from the mold.

Reasons (i think) for the problems

1, - I had the thro-bag connector sitting on the perforated release layer on the part - bad move, it left marks in the carbon and sucked up resin, should i put it off the mold area ?
2 - I think I had miles to much vacuum, I read 20% vacuum, which I read as 20% off full vacuum for some stupid reason which meant I had the bag set 80% vacuum. The combination of this and mistake 1, meant that the pump was sucking up resin through the tube. This probably explains the dry result and the lack of adhesion to the gelcoat. (and a bunged up valve!!)
3. The resin (EL2) is approx 4 years old,left over from a previous job - could it have gone off?
4 The carbon cloth is some I was given 15 or so years ago, unknown thickness and origin, not sure if this matters?

Apart from this it went well :-)
For my next attempt, I will move the thro-bag connector to somewhere off the actual mold area, maybe add a ledge at the side for it.
Reduce the vacuum !!!!. Should I start at high vacuum  to initially bed everything down and the reduce it or just set the regulator to 20 % from the start ?
I think I will make it all from carbon to help with the delamination, or was that just because I sucked most of the resin out. 

Sorry for the ramble, but do people think  I have identified most of my problems and my next go might be better, or I'm talking rubbish (won't be the first time)
Cheers
Eric
By Steve Broad - 11/24/2018 9:09:57 AM

 
Hanaldo - 11/23/2018 11:46:53 PM
Sorry Steve, long day yesterday - I thought you meant combined weight of the finished component rather than individual weights of the reinforcement and resin. Carry on!


:-)  But you made me think for  a bit :-)