Ok this is my first attempt at a resin infusion.Things seemed to go ok, no leaks and setup kept vacuum over the curing time.
The surface which should have a glossy finish seems to be flat on about 90% of the surface. The other 10% seems to be showing the weave as it is not filled in with resin. I am sorry but I do not know the name for this issue (does anybody know the name of this?).

The part seems rock solid, resin was degassed and the part seems correct on the bondable side of the p[art.

I used 375g 5HS 6k Carbon Fibre for the finished side and 300g +/- 45 Biaxial 3k Carbon Fibre for the layers in between, purchased from easy composites. I also used their IN2 Epoxy Infusion Resin,  SLOW.

The part I made is small, approx 100mm square, this is really just a test piece. I did try to pull the resin in kind of slow (sorry not very scientific) but I have a sneaking suspicion that it maybe wasn't slow enough.

I was thinking at one point maybe thats the kind of finish I should expect from the 375g 5HS 6k weave? Is it possible to get a flat surface and is this a fail?

Its really just very lean, you need to let more resin in. Really what's happened is you've infused a very small piece with quite heavy weight reinforcement, so the resin has 'race tracked' across the surface and reached the exit before it has fully penetrated the fibres. Infusion has a degree of lag. What you see happening on the back of the layup is slightly ahead of what is happening on the surface. This effect is worse the heavier the layup is. 

To tackle this, you need to allow some resin to flow out the exit and into the catch pot. This allows the resin time to wet-out the fibres without causing it to become excessively resin rich, but it does waste some resin. Its only necessary to do this for situations like you have here, small/heavy layups. If you were infusing a larger piece with the same weight, the infusion would somewhat regulate itself.

Also consider you are using a biaxial UD cloth which, although it has enough gaps to infuse fine, does take more time for the resin to soak through than an equivalent weight twill cloth.  The race tracking of the resin that Hanaldo mentions is made worse with the slower infusing biaxial. 

You can slow the resin down with a line clamp on resin line and also, for a cosmetic part, allowing the resin feed to stay open for 20 seconds or so after clamping the vacuum line allows a bit more resin in.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I agree that it looks like there isn't much resin... One easy thing is to just cut your flow media back 25mm or so from the vacuum side of the part - so the resin stops and has to flow the final little bit without flow media.  This will allow the "wedge" of the flow front (far along on top, lagged behind on the bottom) to shorten up and help the air get out of the part.  If you are working with slow resin it never hurts to use more of that open time and flow the infusion slower.  Also feel free to clamp it off mid-infusion for a minute or two - this will allow any trapped air to escape up and out to the flow front or into the mesh.

For small parts it with carbon it is sometimes good to skip the surface flow and just let it infuse slowly through the laminate.  The flow front stays more vertical and resin tends to flow better though carbon along the fibers instead of up and down through the laminate - has to do with the smaller fibers I think.

Were there little chunks of resin stuck to your mold surface when you demolded?  Sometimes if there are release issues you can end up with little bits of resin breaking off and staying stuck to the mold - especially if the resin wasn't completely cured (still b-staged).  It would have been hard-ish to demold?

Ok I think when I give this another go I’ll try to be a bit less stingy on the resin. I did admittedly stop it as soon as the infusion had finished. The infusing did go fast, even tho I did try to slow it very slightly

Thanks for the advice

Fantastic advice Warren. I think I’ll def try to pause the infusion process and be a bit more generous with the resin.

I think I’m going to need to add a ball valve somewhere to give me more control. Those little clamps are quite fiddly and finicky for an infusion so small.

I had originally thought that starting small and scaling up would be the way to go. I’m not so sure about this now.

Thanks again

Thanks for the response Hanaldo. Yeah I’ll definitely try to be a bit less stingy on the resin. I did originally try to slow the infusion down with the little clamps but they were pretty finicky, I clearly didn’t slow it down anywhere near enough.

Chris Rogers: thanks for the reply and advice. There wasn’t enough flow media really, that’s something I’ll need to add when I try it again.

Just out of interest when you said letting it soak into the laminate and skipping the infusion process, do you mean not infusing it at all?

I think that Chris meant that you could probably skip using the infusion mesh (flow media) altogether, being that the part is so small. This would give you a very slow infusion that would allow the resin to wet-out the fabric more completely and shouldn't pose any problems if you're using a slow hardener, but it should still infuse in reasonable time on such a small panel

It seems a bit counter-intuitive, but you would likely find things work more smoothly on a slightly bigger panel, as you wouldn't need to worry so much about controlling the resin flow. Infusing small and relatively thick laminates requires more careful planning than something closer to the size of part you'll likely be looking to make in the future

+x

 

MarkMK - 7/25/2020 7:07:34 AM

I think that Chris meant that you could probably skip using the infusion mesh (flow media) altogether, being that the part is so small. This would give you a very slow infusion that would allow the resin to wet-out the fabric more completely and shouldn't pose any problems if you're using a slow hardener, but it should still infuse in reasonable time on such a small panel

It seems a bit counter-intuitive, but you would likely find things work more smoothly on a slightly bigger panel, as you wouldn't need to worry so much about controlling the resin flow. Infusing small and relatively thick laminates requires more careful planning than something closer to the size of part you'll likely be looking to make in the future

Just to say thank you MarkMK for the advice. I’ll try it also without the infusion mesh to help slow it down.

Maybe testing so small wasn’t the greatest idea.

I’ll do a few more tests small and scale it up when I get it right small.

Thanks for helping out!