Hi all, I started playing with composites about a year ago & have learnt a bit since then. All of these parts have been for micro light aircraft. The latest pieces I'm trying to produce are 10mm x 45mm x 405mm bars. My first attempt was just a simple layup sandwedged between 2 molds. The results were that it weighs the same as an aluminium equivalent. So the only way to improve on this would be to do a vacuum infusion.
I made a vacuum pump that pulls about 26Hg max, Is this enough?
How can I insure that the carbon tow is fully saturated at the bottom of the mold?

 The mold is "C" channel & I don't plan on using the second half on the mold.

First of all ... a good pump, that can deliver HARD vacuum is essential !!!

I have had very good results with unidirectional, using a wet lay up and a combination of mechanical pressure and vacuum.

I have made I-bars and U-profiles this way .. much stronger and lighter than same size alu profiles..

In fact I used square alu and stainless tubing as moulds for the profiles.

for the I-bars I milled grooves in two pieces of stainless steel, did a wet layup of 200 g standard twill against the mould, and several layers of unidirectional in between.. The finished parts do not have the most perfect surface finish, since i did not spend much time on polishing the steel...

For the U-profile and bars i used an aluminium square tube, and cut one side off, the one with the seam .. (in the mill ...easiest way ..) The sqare tube has a small radius in the cornes, which is a very good thing..  I used a stainless tube as inside mould, I had to mill that smaller in width to fit, and give me the desired thickness of laminate.

After initial layup i simply bagged them and clamped them very hard using a number of C-clamps.. I also found that one must clamp in the middle and work out towards the ends, the slight flex in the tubes i used makes this work rather well

The longest bar/profile was 400 mm

If you have trouble wetting the unidir in infusion, maybe you should try to wet out the unidir first and the set up a subsequent infusion?

Maybe my initial success is due to using a combination of unidir and ordinary twill--- hmmm...

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