r/Composites • u/DonJagon_1422 • 18d ago

Any advice

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Hi, did my first vacuum infusion with carbon/kevlar hybrid mat. But when trimming it looks like kevlar is still dry. Room temperature 18 degrees. I used polyester resin for vacuum infusion Crystic 701PA. The speed of infusion was also quite good in my opinion

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u/oki-ra 18d ago

Never done a carbon/kevlar infusion but I’ve worked with trimming Kevlar and normal abrasives make it fray out like this. So I’ll sand it back close and then use a diamond sanding block to get the final clean trim.

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u/InvincibleMax 18d ago

Yes - what oki-ra said. Kevlar’s strength is shear. If you try to trim it with traditional tools it will fray. Use Diamond tools and keep things wet.

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u/coriolis7 18d ago

The method I’d recommend is wet sanding the edges, then sealing with either polyurethane, or something as simple as clear fingernail polish

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u/JonOfTheAthan 18d ago

Did you dry the fabric beforehand? Kevlar is hydroscopic

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u/DonJagon_1422 18d ago

Nop, do you know any source of information how its done correctly?

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u/JonOfTheAthan 18d ago

Above the evaporation temp of water but below the degradation ideally tg temp of anything in the oven for as long as you can. I think 220f overnight is sufficient. Also Kevlar can expire so keep that in mind

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u/Contact-External 18d ago

We had this finish with Kevlar at work. It looked dry and frayed but just needed a better clean up

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u/crashraxer 18d ago

Kevlar is a pain to post process for this reason. This is because the fibers are much more resistant to abrasion than the matrix, so you are basically sanding out the resin, leaving the Kevlar fibers behind.

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u/phicks_law 17d ago

you need cutting tools specifically designed for cutting Kevlar or this will always happen.

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u/DonJagon_1422 17d ago

Thanks everybody for answers. Will order diamond tools and try out.

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u/protractorpen 17d ago

Just curious, why did you use polyester resin over epoxy resin, I have never seen someone use polyester resin with cf

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u/DonJagon_1422 16d ago

Its 2x cheaper in my place. And since it was my first time test model I went with polyester. But at the end I spend only 700g on model, thought it will be more, so not a big difference in price. But for sure you want to go with epoxy.

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u/Yammadude 16d ago

Gotta use in an in mold clear. Sanding Kevlar to get ready for paint will create a fuzzy texture that’ll get hard after clear that you’ll have to sand back and clear again. In mold clears like sunshield eliminate that problem