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Thread: is there a good Carbon Fiber Epoxy?

  1. #1
    Senior Member Susqu's Avatar
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    is there a good Carbon Fiber Epoxy?

    I tried a search and got nothing.

    Need some input from users, and not just relying on manufacturing advertisement for what might work well,

    With the growing use of carbon fiber for w/c parts I figured someone would have some experience trying to repair this material.

    I need any feedback, good or bad, of epoxys to try to repair a small crack (in a non vital area, side guards) before it becomes a larger crack. I thought that if I could catch it early I can keep it from getting too much worse for a bit.

    Even if you tried something and it didn't work worth a squat, it would be helpful to know that too.

    Thanks

  2. #2
    Senior Member elarson's Avatar
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    I have also looked into this, because we have a carbon fiber seat base and side quards. I would also be interested in hearing what others write back about repairing cracks like yours or de-lamination.

    For trim, it has been recommend on this site to use a Cyanoacrylate (CA) “Super Glue” like Gorrilla glue.

    I have heard from some people I know locally that Scotch-weld 2216 epoxy adhesive is good, but we have never tried it, so I can not attest to it.
    Partner of an incredible stroke survivor. Limitations: hemiparesis and neglect (functional paralysis and complete lack of awareness on one side). Equipment: TiLite ZRA 2 and 2GX, Spinergy ZX-1, RioMobility Firefly. Knowledge: relative newbie for high-level equipment (2012), but willing to try to help others who are new with similar limitations (definitely not a guru, but inquisitive).

  3. #3
    West System.

    Take it to a boat place or find someone who repairs carbon fiber bikes or hockey sticks - those two things are pretty commonly repaired.

  4. #4
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    West has very good epoxies for doing layups or for doing laminated repairs. But for small crack repair or edge bonding, or even filling very small holes, the best solution is an epoxy repair gel. Gels are easier to control, so there is less chance of ruining the adjacent finished epoxy surface or gelcoat. Gel can be applied to vertical surfaces with minimal sag and no runs. It is an excellent gap filler also. I recommend Davcon’s 5 Minute Gel. Fast, cheap, readily available, very strong, and almost clear when cured. Mix it on a paper plate, and apply it sparingly with toothpicks. If the item is somewhat flexible, bend it slightly to open up the crack, and then apply small amounts of the gel down inside the repair. Let it relax and close back up, and then complete the surface fill. Be very conservative with the epoxy. You can always do a second or third application, but if you get it on the adjacent areas, you will mess up the finish. You cannot make an “invisible” repair, but if you are careful, you can minimize the scar. I usually make a slightly raised mound over the crack repair for additional strength.

    http://www.lowes.com/pd_74434-34278-...ductId=3819909

    Available at most hardware stores, and some department and auto parts. Loctite makes a similar one, but it's a thinner viscosity and it's not clear when cured.
    I also use this to repair nicks in Spinergy’s PBO fiber spokes. Apply it with a small brush. Keeps them from delaminating further.

  5. #5
    Senior Member robotnik's Avatar
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    Repairing some small cracks with epoxy resin is easy if you still have functionnal hands (!)
    Stubby has given the best part of the idea, but may be I can help with some other tricks.
    Before starting, you must make sure that the carbon fiber itself is NOT broken or damaged. A "carbon fiber" part is made of… carbon, impregnated with epoxy resin (most of the time -other resins can be used), and you always have a thin layer, a "top coat" of pure resin on the top. If you bend the part too much, first of all you'll crack the upper layer of resin, then the inner resin, "inside" the fiber, and finally the carbon fiber itself.
    When the carbon fiber is broken, you CAN'T make a strong and durable repair WITHOUT putting on some other layers of carbon. No way !
    Epoxy resin cures easily if you respect VERY accurately the % of parts needed. You also have to mix the two components perfectly. If not, your resin may stay tacky or will not have its maximal strengh. Thus, for small repairs it is easier to use kits, with two syringues of resin parts side by side. It helps a lot to have the good amount of each part. I think the brand of the kit doesn't matter a lot, sometimes you can choose between a clear, stiff, or viscous product. But I hope they all cure well.
    Some warmth is needed for a fastest cure, so don't work outside if it's freezing !
    And at least, if you want to minimise the scar, you can apply (when the resin is still smooth) a band of tape on the repair (use the brown tape that closes carton boxes) and "laminate" it the best as you can. Then wait for the cure and "demold" it, this method gives a nice finish !
    C6-7 since mid 2002, no hand control nor triceps.
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  6. #6
    Senior Member elarson's Avatar
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    Great information guys -- Thanks. Although we do not need it yet, it's good to have available when we do.

    Susqu, post back and let us know how it goes. I'd be interested in seeing before and after photo's if you can manage it too.
    Partner of an incredible stroke survivor. Limitations: hemiparesis and neglect (functional paralysis and complete lack of awareness on one side). Equipment: TiLite ZRA 2 and 2GX, Spinergy ZX-1, RioMobility Firefly. Knowledge: relative newbie for high-level equipment (2012), but willing to try to help others who are new with similar limitations (definitely not a guru, but inquisitive).

  7. #7
    Suspended Andy's Avatar
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    My favorite is JB Weld. But if you want to get classy...check out the Hysol line of epoxies. I'm sure there is one there that describes the fix and recommends a version for what you are looking for.

  8. #8
    There a couple things to consider before you fix carbon fiber. The part is made by taking carbon fiber woven matting and soaking it in liquid resin. If just that resin is cracked you can do what Stubby or Robotnik explain. If the part is cracked in or through the matting you should do as Jeffadams says and take it to someone that does this stuff all the time. Boat people and certain body shops specialize in this stuff. If the mat is cracked you may be able to stop drill it. A small hole drilled at each end of the crack could keep it from going further. This works on metal. I've not done it with carbon fiber.

  9. #9
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    A stop hole works in metal because it is a monolithic ductile material and the stress can be redistributed evenly. A carbon fiber plate is a built-up composite – basically an assembly. A crack always forms in the weakest part of a composite, and will continue in the weakest direction. Once a portion of the assembly is separated (cracked or drilled) the stress will still want to continue along the path of least resistance. Like a crack in a concrete slab (also a composite).

    Basically, torn carbon fibers themselves cannot be repaired. They can only be reinforced adhesively via resin. Even a fully laminated repair does not “fix” the torn fibers below. It just basically creates a new panel on top of the damaged one. But it also doubles the weight, which was the primary reason for using CF in the first place. On a non-loaded item, like the OP’s sideguards, epoxy alone can make a surprisingly strong repair, because it creates an adhesive reinforcement of the torn fibers.

    Professional repairs can be very expensive. If aesthetics or absolute structural integrity is the primary concern, it’s probably cheaper to replace it rather than repair it. If you like to get your paws dirty, try the simple crack repair. If it doesn’t hold, you can always add an overlay patch. If that doesn’t suit, go fully laminated. Of course, once you have the mad skills to do a full overlay, you can just as easily lay-up a complete new one…

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