glossy finish both sides

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#1

Hello everyone,

I recently got into making carbon fiber and I am currently experimenting with making parts. I am noticing the longer I have the epoxy sit on the mold before I lay the first layer of carbon fiber down the shiner that side gets. I am using a perforated release film on top of the carbon, then breather, then vacuum bagging it. The non mold side comes out very dull and bumpy.

What are some of the ways to make this side shiny like the mold side? I need both sides of the piece to look glossy.

Also, I am noticing sometimes on the mold side, there are small areas where the resin does not appear along with the rest. I added some photos to help show what I mean.

Thanks for any suggestions or tips.

-Brian

Centri Designs

#2

If you are making anything other than flat sheet, then only way to make the reverse side glossy with typical wet lay vac bagging is to refinish that side once it’s cured. This means sanding that side smooth (touch easier if you use peel ply but still a bit of work), and then clear coating the back with lacquer or resin. You’ll probably then need to flat back at least once more before polishing. It’s a tedious task, so decide how much you really need that reverse side to be glossy.

As for the problem in your photos, that is caused by too little resin. Either you aren’t putting enough in, or you are drawing too much out. I like to make the first layer quite resin rich if it’s a cosmetic part, and then do the rest as per normal.

How hard a vacuum are you pulling? You can actually squeeze out too much resin if you apply too high a vacuum (assuming you are using absorber of course). With wet lay vac bagging, I try not to draw more than 80% vacuum. You’ll end up with a more resin rich part, but at the end of the day, does that matter? A few grams extra weight is normally worth it for a perfect cosmetic finish.

#3

Hanaldo,

Thanks for the detailed explanation. I am probably pulling too much of a vacuum so I will try to pull it a little less next time. A few oz doesn’t matter at all for what I’m making.
What type of clear coat would you recommend? I would probably want something thicker so that it doesn’t run down the part since its curved.

It’s crazy that to get the back side glossy requires that much work. Does anyone else have any tips or suggestions to help get the back side glossy without going through the whole sanding and clear coat strategy?

#4

Hi Centri,

you can obtain a shine side on back surface of the part if you use a back mold made by siliconic gum for example or fiberglass, but you have to change manufacturing system to vacuum injection
https://www.youtube.com/watch?v=yTsXKGUdtCE

#5

Interesting approach to the problem. Thanks Simontech

#6

Can Vaccum infusion be used on a closed mold… injection equipment is super expensive!

#7

To a degree.

With infusion you need some form of flow media to allow the resin the move through the laminate. You obviously can’t go the regular route of having the flow mesh on top of the stack, as this will ruin the aesthetics of the B-side. So the only option is an internal flow media. Materials like Soric would work if your part can be thick enough to utilise a core material, but other than that the only option would be to use a flow mesh that can be left inside the laminate without affecting interlaminar bond strength. The other problem being that flow meshes tend to use a lot of resin and not contribute any strength, producing a heavier part without any structural gain.

#8

Thank you hanaldo, following up with another question, planning on using lantor soric in between the laminate, need two sheets of sizes 2 and 2.5 mm.
What i would be doing is engraving credit card business card holders into the laminate, with the soric in between would it by any any affect the final result. The 2mm sheet will have a 0.76mm depth engraved into it by CNC.
Any experience cutting or engraving these kind of laminates?

#9

Are you OK with having the core exposed at the cut out? If not, you’ll want to make sure your laminate skins either side of the core are at least 1mm.

#10

not okay with the core exposed unfortunately, but will test working out how i can manage the skins properly, so vacuum bagging with soric as core sounds good, what about the b side mold, mylar? what do you think will be the best to get a nice surface finish.

#11

If it’s anything other than just a flat sheet then it would need to have a matched mould.

If it’s a flat sheet, then Mylar works but can be tricky if you’re not practised. Two glass panes also has its drawbacks. It’s not the easiest thing.

When you say vacuum bagging, do you mean wet-lay or infusion?

#12

Any advantage to use Mylar with infusion? What exactly does it do? From my knowledge it’s like a stiffer peel ply but does it give a flatter better surface?

#13

Mylar is something to give you a good surface finish mate, but from what i know it does not have the same function as peel ply.

Hanaldo, have a quick question, can you identity the fabric used in the below video on the wallet?
Also can you identity what kind of method used to create that kind of glossy finish?
Clear coating after or its just what comes out of the mold?

https://www.youtube.com/watch?v=4ftE8Qr8TQg

#14

Looks like a regular 200g 3k 2x2 twill weave fabric to me. Judging by how compacted the fibres look on the surface, I would say that they have used a press, although that isn’t necessarily true. And it doesn’t look clear coated, I would say that is straight off the tool surface.

#15

thanks hanaldo, so happy we have this forum and guys like you to help the inexperienced. thanks for all the help, hope you have a great day god bless!!

#16

Isn’t it total irrelevant for your application if the sheet is 2,2.5 or 3mm thick? You can use a knitted transparent flow media between your layers and infuse between two sheets of glass.
The next question is, how big should your sheets be? I was thinking about 1.5-3 square meter, but if I am right yours can be 100x100mm or so. It that is the case you can do that without flow media or buy a cheap workshop 20 ton press amd two heated small ates and press prepreg panels on your owen.

#17

dear ddcompound, thank you for your suggestion

i have access to only vaccum bagging as of now, could you please elaborate any other mould i can use apart from glass to create sheets round 2mm and 2.5 mm

i have wet layed between glass plates before, got an above average finish which im pretty happy with but not very consistent because on some occasions the upper mold cracks when releasing the part. So its very inconsistent. i assume i might have the same problem vaccuum bagging as well.
So can you elaborate what kind of transparent flow media knitted available as of now? Also what else can i use instead of glass? something unbreakable and has a decent mold life providing a quality finish in your experience?

#18

If your glass breaks you have a release problem. I would stay with glass. This flow media becomes transparent when saturated.
http://gerster-techtex.com/en/composites/resin-distribution/352-2/

#19

Are you just using release wax on the glass? Release wax is very inconsistent with glass because glass has very little porosity, so often the wax doesn’t actually ‘stick’ at all and is removed entirely when buffed off. For this reason, sometimes it works and sometimes it doesn’t.

I’d recommend using a chemical release agent like Frekote or Easylease or whatever is available in your area there’s a lot of options out there. But chemical release agents work extremely well with glass and you will easily get 10 or so pulls from the tool before you need to apply another coat of release agent.

#20

Dear DD Compound, the flow media you linked too is great but the thickness is 1.5mm. For my application the thickness of my laminate is around 2mm and then its machined into a business card holder.

I am guessing the thickness of the flow media is too thick to begin with? another scenario could be that under the pressure of the vaccum the flow media gets compressed as well, if so what kinda thickness will the flow media have post curing inside the laminate…

Also do you know of any other interlaminar micro mesh flow media available around0.5mm in thickness

i think this will be perfect for my application