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Bonding C/F tube into a Alum. housing
Alan B - 5/12/08 at 08:31 PM

I have a work challenge coming up. I have to attach a 26mm OD C/F tube into a Alum. housing. The housing bore can be whatever in needs to be for the right fit and the engagment length is about 125mm.

Prefer not rivet or fasten mechanically, what about bonding?...easy?

Any advice is welcome.

Cheers,

Alan

02GF74 - 5/12/08 at 08:39 PM

hmmm, you may want to ask this on a biking forum - carbon fibre and aluminium are often joined together but usually it is the aluminium sitting insdie the CF tube held together by some resin. I am sure it must have been done other way too.

adithorp - 5/12/08 at 08:53 PM

Alan c/f bike frames circa late 80's were tubes bonded into ally housings. They were renowned for coming un-bonded. The common repair technique was to re-bond/glue with araldite. Never saw one fail again once done. A mate (bit of a retro freak) is still using one that he glued at least 15 years ago.

adrian

richmars - 5/12/08 at 08:54 PM

Yes, bonding's the best way, Ideally you don't want to drill into the carbon.
Also consider galvanic corrosion. You need to electrically isolate the carbon from the Al. You can use a layer ot tow of glass fibre.

Alan B - 5/12/08 at 09:13 PM

Thanks guys...so it looks like epoxy/araldite is the way to go.

BenB - 5/12/08 at 09:39 PM

I can confirm that araldite bonds to ali extremely well and what with CF GRP (by default) being epoxy you'll get good adhesion...

Chippy - 5/12/08 at 10:12 PM

Any bond between C/F and alloy will be mechanical, so make sure that the bonding surfaces are ruffened (sp) well. Cheers Ray

Fred W B - 5/12/08 at 10:30 PM

If it wasn't midnight I would go and take a pic of the 80's Vitas road bike I have in the loft. As said above, it has carbon tubes bonded into alloy lugs, with the overlap a lot less than 125mm, so you should be fine

Cheers

Fred W B

[Edited on 5/12/08 by Fred W B]

Hammerhead - 6/12/08 at 10:34 AM

quote:
Originally posted by richmars
Yes, bonding's the best way, Ideally you don't want to drill into the carbon.
Also consider galvanic corrosion. You need to electrically isolate the carbon from the Al. You can use a layer ot tow of glass fibre.


Make sure that the cf and Ali are indeed isolated from each other. Do F1 teams get round this by using titanium?

Jason Fletcher - 6/12/08 at 12:01 PM

The absolute best product for bonding carbon to ally is a something called Hysol 9462. I use it all the time when building jet powered model aircraft and it will never let go. It's not as brittle and much easyer to work with than Araldite.

I have been bonding ally to carbon for 15 yrs and never seen or heard of ally-carbon corrosion so I would say theres no need to protect aly from carbon.

You can get a 50ml tube from Motors and rotors on 01923 270405

Use it, you won't get anything better!

Jason

Alan B - 6/12/08 at 01:49 PM

All good stuff...I knew you guys would have the answers.

Cheers,

Alan

Mix - 6/12/08 at 02:35 PM

Hi

As per Jason above ....... the aircraft industry has been using Hysol for these types of structural aplications for years.

Regards Mick

Alan B - 8/12/08 at 07:16 PM

Another question..

What operating temperature range would you imagine was possible for the Ali/hysol/CF component.?

In service in could be stored in the back of a van in summer (quite hot) and used outside in the middle winter in very cold locations.....in other words both extremes of natural ambient temperatures....

I'm guessing the failure mode in this case would be down to the differential expansion of the joined components?

Cheers,

Alan

[Edited on 8/12/08 by Alan B]