Too dry?

General Composites Discussions Composites Talk
#1

Hello,
I have been using a vacuum system to create some tubes for a bike. My main concern is that the tubes are coming out dry. My method currently is to cut foam cores, wrap with carbon fiber while wetting out, wrap in nylon peel ply and then bag it.

On one batch of parts, there are some sections where I can feel carbon threads but it seems saturated and hard. On the first bag I did, the entire tube has the texture from the peel ply and I am very satisfied from the result. This tube can be seen on the right of the image. The next left two are from the same batch and are questionable quality.


High Resolution: http://i.imgur.com/BlLiMJG.jpg

My main questions are:
[ol]
[li]Should the parts look like the one on the right?
[/li][li]How saturated should the fibers be during layup?
[/li][li]What’s the best method for wrapping the carbon tightly around the tubes so that it doesn’t wrinkle?
[/li][li]How do I prevent the peelply from moving while in the vacuum bag?
[/li][/ol]

#2

you answered your own damn question

#3

I would suggest using release coated shrink wrap or tube instead of the vacuum bag.

#4

are you using release film and breather with your peel ply? r just peel ply? You might be suffocating the vacuum in your part from really being effective. Have you considered just using heat shrink tape instead?

#5

If your doing wet layup, you should be using shrink wrap. It’s cheap and works very well. I’ve made tubes like this and they come out great. This is how professional tub makers do it as well. It helps to have a jig to wrap the shrink wrap in an even layers so you get more even compaction. The wrap does leave a bit of an impression that can be sanded off afterward.

#6

Not sure shrink tape would work well with a foam core, would probably deform. Let the layup tack up a bit before you wrap and bag.

#7

Thanks for the replies. I did another batch making sure to use more epoxy on the lower layers. I think the problem stemmed from me using a brush and only adding epoxy in one direction which left some areas dry.

I decided against shrink wrapping the tubes because some of pieces I’m making more than just tubes and vacuum bagging was necessary for the other shapes.