Two sided infusion issue

[deadgrateful]

Hi guys, I'm a furniture/industrial designer and after doing a few infusions I'm absolutely hooked on composites. The possibilities in my field are endless and are barely being touched upon.

I'm currently working on a chair design which is a continuous curve and is usable in two different seating positions (reclined and social). The pattern (plug?) is made and all polished up ready for an infusion and I have an exact 1:6 scale replica for which I've been using to create the test models. I'm having issues with achieving a decent surface quality on the outside face.

I should mention that the final finish I am after on the outside face is the textured matt surface that peel ply leaves. This means that sanding isn't an option. The inside face is glossy.

All layers are securely tacked into place with epoxy spray adhesive.

The first test had the following layers (working from the inside out):

pattern surface > 3 layers of 200gsm 2/2 twill carbon > peel ply > easy flow mesh > vac bag

This resulted in a thickness of 0.7mm. The inside face was perfect and the outside was a little bumpy.

The second test was closer to the final desired thickness of 5mm and had the following players (from inside out again)

pattern surface > 1 x 200gsm 2/2 carbon > 1 x 650 gsm 2/2 carbon > 1 x 2mm lantor soric > 2 x 200gsm 2/2 carbon > peel ply (for finish effect) > vac bag

This resulted in a thickness of 3.5mm. The inside face was again perfect but the outside had a very undulated finish with light bunching. The infusion spiral and connectors left deep marks but on the actual pattern this won't be a problem as I have included wide flanges and they will be placed to the sides. This finish isn't even good enough for sanding and then skinning over with a light weave...

I can replace the Lantor Soric with a few layers of 650gms carbon which should give me a slightly better finish I guess... But this would reintroduce infusion mesh and would leave different marks.

So my question is how can I get a nice level and flat peel ply finish on the outside face? I'm pretty much up for trying anything at this point! If this isn't at all possible, what other options do I have? (an outside gloss face wouldn't be durable enough for a chair).

Any help would be extremely appreciated as I'm tearing my hair out at the moment!

Pics here: Link

 

[jotunn]

It's a bit of a long shot, but:

I've seen anomalies like that occur as a function of high cure vacuum. If you have the time for experimentation, try infusing at full vacuum but then decreasing the vacuum during cure to...say...10"Hg.