Carbon Fibre Wing Mirrors


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I've been making carbon parts for a while and never really had any issues. Most of the issues ive come across ive been able to workout what went wrong and fix it for the next time.

I made moulds for some carbon fibre wing mirrors using the uni mould system as with everything else i make. However with these i cant workout where i am going wrong and how to fix it. I will detail below my layup process and then the issues that i have. The mould is prepared with the usual 6 coats of easylease.

Layup;
- Due to the shape of the wing mirrors laying in one piece of carbon proved very difficult so i cut two seperate pieces. I need a precise cut on one so i use pro-finish 210g 3k carbon for the front section and then the standard 210g 3k carbon cloth. I do 2 layers of 210g cloth, but for the backing layer, for ease of layup, i cut it into some smaller square sections. These are all laid into the mould using Aerofix 3 spray adhesive. The cloth is cut right upto the edge of the shape of the mirror. I did try overlapping it onto the flange but this just caused more issues with it snapping or cracking trying to get it to release.
- Peel ply - again cut into smaller shapes to conform to the mould and applied with aerofix 3
- bread wrap - I cut this into smaller pieces and hold it in place with a bit of masking tape.
- infusion mesh
- I also leave a resin break
- using IN2 infusion resin which has been degassed

The issues i am facing;

- Can barely get the part to release... sometimes it will crack the carbon around the edge trying to get it out and it has also damaged the surface of the mould, pulling out some of the gelcoat
- pinholes / voids
- the mould is complete mess after each infusion, so much so that i had to resand the whole thing after the first attempt as the flashing round the edge was completly stuck on and its pretty much the same again after the second attempt.

So what should i change? Should i make a split mould instead? Should i slow down the infusion process? Why would the mould surface chip away and be stuck onto the part?

Any help would be much appreciated.






Warren (Staff)
Warren (Staff)
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Its hard to say in the pictures if the shape alone is the issue but I doubt it.  

The fact it is tearing chunks out of the gel points to a more fundamental issue with release.  An awkward shaped part would not tear chunks like that.

I would have a look at your release agent. Make sure its not too old or gone bad and clean everything back and start afresh with new release agent.  With something like EasyLease, the release aspect is generally not difficult.

Also check your cure times.  IN2 with the slow hardener can take up to 30 hours to cure at 20C so if you demould too soon, the epoxy will grip the mould while it is green and that alone can cause major release issues and mould damage - part cured epoxy grips very well!    Also properly check your temperatures as if it is cooler or cooling overnight, that again will extend cure times.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
MarkMK
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As Warren said, it does like you are not getting a very good release

If you're using a chemical agent like Easylease, before the first pull I'd likely look to apply around eight coats, just to be certain of things coming out cleanly.

I regularly make a similarly-shaped part (mirror covers) and I have to be careful when removing the peel ply that the part doesn't come out too soon, as the subsequent single application between pulls means that very little is needed to get the remove it. 

As an alternative to your current fabric choice, you might want to try using a 240g twill instead of the 210g and Profinish? It's very stable and I only use two layers of this for the part I make. It is sufficiently strong also, given the curved shape and conforms really well in a single piece without distortion.

There's also no issue with the overlap onto the flange cracking during de-mould, when a gentle easing with a wedge is needed. The mould has been well used, though, so the build-up of release agent helps a lot.
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