Hi all,

I have a few questions about making flat carbon fiber sheets and hollow rectangular box channel.

When making a flat sheet under a vacuum, (or anything for that matter), what kind of release film should I use? From what I have read, Peel-Ply and Porous release films will allow excess resin to be pulled from the layup, but a non porous release film doesn't? But parts created with the non porous release requires less finishing, is that correct?

Second, I'm looking to make a box channel by wrapping a piece of Styrofoam with carbon fiber, then remove the stryofoam with acetone. I've already created a piece like this, but since I don't have vacuum equipment (yet) the finished part was rounded and not square like the stryofoam. I assume creating the part with a vacuum will make the carbon fiber conform to the square shape better.

I'm working on really small parts here, The box channel is made using a piece of 1/4" x 5/8" stryofoam and I wrapped it with 5 layers of 5.7 oz/sq yd .012 thick fabric. I was aiming for the side walls to be 1/16" thick. Would a thinner fabric and more layers work better to create a square part, or thicker & less layers?

Thanks for any help,
Randy
 

With Styrofoam you have to be careful because the foam will crush with too much vacuum. For something that small with that many layers you will probably want to get some aluminum to use as a mandrel so you can give it as much vacuum as possible. Also maybe look at braided sleeve as wrapping cloth around square mandrels can be hard. Just make sure you release it super well, getting the part off can be difficult. Some times it helps to leave part of the mandrel sticking out one end and laminate off the other end so that you have two places you can attach things to to assist in pulling the part off the mandrel

Non-perf release film would only require less finishing because it would make a very resin rich part. Cosmetically this is better, but it would be a weaker, heavier part. 

Hey, thanks for the replies!!

My first attempt at making the box channel was using an aluminium mandrel. The aluminium was quite smooth, so I sanded it with 1000 grit sand paper with a small palm vibrating sander.  I then applied 5 coats of partall paste #2, a mold release wax, buffing between coats. The instructions said the wax didn't need any drying time and I could start buffing right away, which I thought was strange for wax. Apply a coat and buff, repeat another 4 times, wrapped it with carbon fiber, wetting down the cloth as I went, using west systems 105 epoxy and 206 slow hardner. I had read that freezing the aluminium and carbon fiber to -50 degrees would shrink the aluminium more than the carbon fiber, making removal easy. I placed my parts in a -10 degree walk in freezer, the two loosened up, but I couldn't get the aluminium out.

I left both ends of the aluminium bar exposed, so thanks for the tip of having only one end of the bar exposed the carbon fiber on the other end would help, giving me a way to grip each material and pulling them apart. Anyway, I'm not someone that gives up easily. Sodium hydrochloride is supposed to dissolve aluminium, so I left everything soak for a week in a house hold liquid drain opener that contained the sodium I needed. That didn't work either, so that's when I decided to use stryfoam/acetone combo. Any suggestions as to where I went wrong?

Can someone please describe consolidation as it relates to this? What does it mean in this context?

So the idea of using formers, that would be making a box with the inside dimensions matching what I want the out side dimensions of the finished part to be, then clamping the formers down on the laid up fiber? If so, that sounds like a very easy method for a one-off or a few-off parts.

I will be buying vacuum equipment soon, just not now, because coming cold winter temperatures and an unheated workspace will prevent me from working on this.

If I am correct about the use of formers, I may buy the materials I need to try this method quickly. Hoping for one last nice summer day before winter, or use electric heat to keep it warm while curing.

Thanks for the advice so far,
Randy