Leave remarks to let me know what you think of it and where I could improve, be more clear. Are there some new tutorials you would like to have on how to work with composites, like carbon fiber, let me know as well!
Personal website: http://www.matthieulibeert.webs.com
Step 1: Step 1: Safety
That said, lets start the tutorial.
Step 2: Step 2: analyzing the broken part
Step 3: Step 3: Preparation of the rest of the frame
Step 4: Step 4: Clean the broken part
Step 5: Step 5. Sanding the part
Step 6: Step 6. Clean the part you’ve just sanded
Step 7: Step 7. Filling the repair with Graphite mixed with Epoxy
First mix the Epoxy A+B then add the graphite powder. You should check the technical page of the epoxy you are using for mixing ratios. Once A+B are mixed you add some graphite powder. Add enough to get a more viscous paste you can apply on the part without everything running of.
Note: This isn’t enough as a repair!
Step 8: Step 8. Put the mixture on the repair
Step 9: Step 9. Sanding
Step 10: Step 10. Vacuumbagging materials
Ive used some Carbon fiber twill weave. First layer is a 200g/sqm followed by 2 layers of 400g/sqm. See how it’s layed down? Direction of the pattern: “/////” followed by “\\\\\\“ this will give extra strenght on torsion and pressure.
Peelply is a release cloth. It will make it possible to remove all layers laying on top of this (perforated film, Breeder). It also gives a nice grip if you’d like to add some layers on top of that. Meaning you won’t have to sand it again if you would like to do that.
The perforated film (bleu) Has some tiny holes where the excess resin can pass through.
Note: It is not the resin that gives strength to a part but the fully saturated Carbon fiber cloth making a good matrix with the resin.
The breeder is there to take care of a good vacuum all around the part and sucks up excess resin coming through the perforated film and peelply.
Sheet of special plastic that does not stick on epoxy.
Step 11: Step 11. Vacuumbagging
Put you carbonfiber on a sheet of plastic and pour some epoxy resin on it. Squeez it on to Carbonfiber cloth till it is fully saturated. Then remove it from the plastic and wrap it around the part that needs repair. Do this with all the carbon fiber
You need a vacuumpump to achieve a good vacuum, causing some pressure on the part and sucking out the excess resin. This pump achieves a vacuum of 99.8%. DO NOT LET THE RESIN ENTER THE PUMP OR YOUR PUMP WILL NOT WORK ANYMORE!
Tacky tape (mouldable high tack tape: yellow)
This can easily be wrapped around the the part at both ends of the repair. Put the vacuumbag on top and ensures full vacuum without any leaks
Step 12: Step 12. Vacuum
-> Carbon fiber -> Peelply -> Perforated Film -> Breeder -> Vacuumbag with Tacky tape
You can put on the pump. What you’ll see is some small dots of resin passing through the perforated film. This is excess resin of the saturated carbonfiber cloth that is being absorbed by the breeder. Check for leaks, once you have full vacuum let the pump on for 15min than clamp of the hose and shut down the pump. Let it cure overnight now and if you are able to add some heat, do it for a better and faster cure.
Step 13: Step 13. Remove excess material
Step 14: Step 14. Sand the Carbon fiber smoothly
Step 15: Step 15. Finishing coat of Epoxy
Mix a new batch of epoxy resin to ‘paint’ on top of it. This will bring the beauty of carbonfiber back.
First clean the repaired part with some acetone or cleaning alcohol to remove any dust of the sanding. Mix a small batch of epoxy and let the bubbles get out of the resin. Give it some time. Small tip: Heat the resin a bit in an oven to make it less viscous and more easy to brush on. Entrapped air will get out more easy as well.