carbon fiber repair...

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carbon fiber repair...

Postby LoveB » Mon Jan 14, 2013 9:47 am

hi all, is this worth repairing?I cant seem to locate another rear chainstay for it yet. tis a 2005 jamis dakar xc pro

Image

the carbon seems to just have de laminated from where it attatches to the dropouts. Not sure whether I can try getting some epoxy on it or if i still need to add carbon wrap. Thoughts/suggestions please? thanks!!
Image
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by BNA » Mon Jan 14, 2013 9:55 am

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Re: carbon fiber repair...

Postby Mulger bill » Mon Jan 14, 2013 9:55 am

Looks like the bond has failed and the stay has pulled away from the yoke. Can you measure the length of each side?
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Re: carbon fiber repair...

Postby LoveB » Mon Jan 14, 2013 10:04 am

took a few more pics..

when untouched its like this
Image

if i pull on the chainstay and dropout its like this

Image

and this is what seems to be left of what was in between
Image

Do you guys think I can get away with just epoxy?

both chainstays are still at 14' so its only the bond between the chainstay and the dropout thats been broken
Image
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Re: carbon fiber repair...

Postby Mark Kelly » Mon Jan 14, 2013 10:41 am

If by "just epoxy" you mean what you can buy at the hardware shop, then no.

When you read the following you may well decide to get the repair done professionally. If so, may I recommend Raoul Luescher at Luescher Teknik? I'm not affiliated in any way, I've just had the chance to quiz Raoul on a couple of occasions and he's been incredibly generous with his time and expertise.

Bonding composites to metals is not easy, you need really good surface prep and the right adhesive. I'm using Huntsman (Araldite) 420 A/B available from Meury - it's a little over $300 for a 1.4 kg pack (the minimum you can buy). ATL composites recommend their R15 which is a fair bit cheaper, I would have tried that if the local distributor wasn't useless.

From your phots it looks as though you could unbolt the metal part and separate the two pieces. If you can then you should be able to do the repair. If you can't then you'll have a great deal of difficulty doing the surface prep and without good surface prep the best adhesive in the world is not going to stick properly.

If you can get the parts apart, the first thing to do is to get all the old epoxy out so that you've got the correct bondline gap. Once this is done, sand the inside of the composite part with 120 grit paper just enough to get a surface tooth for the adhesive to grip. Clean this surface with acetone. Sand the parts of the metal piece which will form the bond down to bare metal.

The best surface treatment for aluminium I have found is phosphoric acid anodisation and fortunately it's very easy - you can buy 85% phosphoric at homebrew shops. Cut this 3 : 1 with water to get a solution of about 20% in a plastic or stainless steel container. Need I say be careful with the acid solutions - hint: if it strips anodising off aluminium it's not good for your skin or eyes. Wear protection. Always add acid to water, not water to acid.

Suspend the part to be anodised in the solution. If using a stainless container the container forms the cathode so the part to be anodised must not touch it. If using plastic suspend a stainless steel cathode in there, again no contact between electrodes.

The activation voltage is 15V which can be conveniently obtained with a switchmode laptop computer power pack (Toshiba units have the right voltage, some others brands may do as well). Anode is positive, cathode negative. The solution will heat up due to the power dissipation, properly you should recirculate it to cool it but I just turn it off, take things out and let it cool down then start again. A total of about 10 minutes will give you a good surface. Note that this process will completely strip the existing anodisation off the part, so if you want to retain the black surface you need to protect it from the solution.

As soon as the process is complete, remove the part and rinse it with water then again with distilled water, then air dry it gently (a hair dryer works). When it's dry, coat it with a low viscosity laminating epoxy and put that through its cure cycle. The phosphate coating is very porous and the laminating epoxy will flow into the pores forming a very strong bondable surface. This is the key to the technique. The porosity also means that it's very easy to contaminate if you touch it or let anything get on it, that's why you should coat it straight away. Once coated it"s fine.

Now you have two parts ready to bond. Do a dry fit to check bondline gap - the two parts should slip fit together with little movement but should not bind, nor should there be any large gaps.

If all is OK, clean the parts again with acetone, mix the adhesive and apply it to both parts, making sure you get complete coverage. Push them together and clamp in place.Clean up excess with acetone (much easier than grinding it off later).

If you are room temperature curing, leave the bond clamped for 24 hours and do not stress the joint for at least 7 days at 20 degrees. If you are using a controlled temperature oven, take it to 40 degrees for an hour then to 50 for four hours to cure. Bond strength is improved if the joint is then heated to 70 degrees for up to 24 hours. These recommendations are for the Huntsman 420 A/B epoxy I mentioned. If you use a different epoxy, read the manufacturer's application notes for recommended cure cycles.
Last edited by Mark Kelly on Mon Jan 14, 2013 8:53 pm, edited 2 times in total.
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Re: carbon fiber repair...

Postby mitzikatzi » Mon Jan 14, 2013 12:49 pm

In another thread I have seen a "carbon repair" place in Sydney recommended.
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Re: carbon fiber repair...

Postby ozzymac » Mon Jan 14, 2013 1:00 pm

Hi,
If you have a copy of the last Bicycling Australia magazine there was a place advertising in it that does repairs and frame resprays.



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Re: carbon fiber repair...

Postby jacks1071 » Mon Jan 14, 2013 3:57 pm

That looks heaps easy as a DIY repair. You just need the right stuff to bond it back in with, finding what to use and being able to buy it in a small quantity will be the tricky part but I'm sure you'll work it out :-)
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Re: carbon fiber repair...

Postby geoffs » Mon Jan 14, 2013 7:54 pm

Marks reply was very interesting reading.
Which i suppose was the long of it :-)
The short is if you want the repair to be done properly and you live in Vic give Roal a ring.
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Re: carbon fiber repair...

Postby gururug » Tue Jan 15, 2013 7:56 am

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Re: carbon fiber repair...

Postby jacks1071 » Tue Jan 15, 2013 12:23 pm

gururug wrote:Get a 3d printer

http://www.youtube.com/embed/313vnGBJZdc


wow, that is amazing!
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