Gluing aluminium sleeve into carbon frame

[VooteleAer]

I managed to destroy my carbon frame-s bottom bracket, I had an aluminiun sleeve adapter glued into the frame and while stepping particularily hard onto pedal, that sleeve slided out (and cut the Sempu torque sensor cable). I'm into process of repairing it, so, what glue you would recommend to make it bulletproof?

 

[PaPaSteve]

Highest strength = e-120hp
Second highest = JB Weld

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

Clean well
Sand both sides with 80 grit
Clean with isopropyl alcohol
Glue

 

[Papa]

Bonding aluminum tubes to carbon fiber tubes is generally discouraged. Why?...
Because they posses different thermal expansion rates. CF & titanium is a much better match. That said, I would discourage any epoxies that produce brittle joints. If I had little choice, I'd use T88 adhesive 2 part epoxy. It's what was recommended when bonding aluminum ribs to wing spars on the Kitfox experimental homebuilt aircraft. I would not use JB weld - much too brittle.

 

[PaPaSteve]

T88 specs do look good.
My experience with composites was on the Makani electricity generating kite. (2008 to 2011)
Using an Instron testing machine we did quite a bite of material strength testing on composites and bonding aluminum, titanium metal components to composites .
For what ever reason System 3 epoxies were not included in the testing cycle.

JB Weld tech sheet does show good flex strength, 7320psi and an unusual property of zero shrinkage when cured.
Available at any hardware store.

 

[VooteleAer]

T88 specs do look good.
My experience with composites was on the Makani electricity generating kite. (2008 to 2011)
Using an Instron testing machine we did quite a bite of material strength testing on composites and bonding aluminum, titanium metal components to composites .
For what ever reason System 3 epoxies were not included in the testing cycle.

JB Weld tech sheet does show good flex strength, 7320psi and an unusual property of zero shrinkage when cured.
Available at any hardware store.

In Europe. Still haven't found a reseller. The search continues.

 

[VooteleAer]

How about pulyurethane glues, elastic ones?

 

[marvin78]

In Europe. Still haven't found a reseller. The search continues.

T-88 Building Glue (Quart) from Aircraft Spruce Europe

www.aircraftspruce.eu

Isn't this what you guys are talking about?

edit:

T-88 is a non-brittle structural adhesive which gives superior finished results even when used under adverse working conditions. T-88 will cure in temperatures as low as 35°F which makes it an excellent choice for homebuilders living in colder climates. It is recommended by the builders of many types of homebuilt aircraft and is excellent for bonding aluminum, steel or wood. When fully cured, it is not affected by water, oil, gasoline and most other chemicals.

Seems to be the right stuff. Not sure if 1kg is a lot, it does sound like it and it's 65 euro which might not be the application amount and price you need for your bottom bracket. But it does seem like the right stuff, I just can't find something you can order for smaller quantities.

 

[VooteleAer]

Maybe I can purchase it for the company I work for, they always need a good epoxy for some projects.

 

[PaPaSteve]

Is there a local airport with a small aircraft repair facility ?
They might have small packets of repair epoxy like this :

Hardman 3.5g double bubble epoxy

Airframe mechanics would purchase in bulk.
It's what was used between panels (plus rivets) to build this aluminum monocoque streamlined recumbent.

 

[Chalo]

Gluing aluminum to CFRP often results in galvanic corrosion and debonding unless the carbon fibers are electrically insulated from the aluminum. In the industry, that usually means a layer of glass fiber or other non-conductive material precedes the carbon fabric in the layup.

 

[PaPaSteve]

Alodine is another simple corrosion prevention technique for aluminum bonding.
Can't recall ever seeing a failed carbon bicycle frame that used either process.
Using mechanical shapes on the aluminum like machined tapers, grooves or ridges could have prevented adhesive slippage as well.

Here is an example of a carbon fiber propeller blade the has a 2 degree taper getting larger towards the hub center to prevent it from coming undone.
This is a production reject for a tri blade propeller that spun to 5,000 rpm.


Once the repair is cured, drilling and tapping thru the carbon into the aluminum for a small 3mm bolt or two could give piece of mind.
Providing there is enough room for a small bolt ?

 

[VooteleAer]

Actually I had one 3mm bolt through the bottom wall. In the bottom there's a hatch that acess small compartment for routing cables I guess, and there's quite thin carbon wall between the hatch and sleeve. I had it drilled and threaded. When the accident happened I guess the bolt snapped, I haven't found the head of it.
Also, the bottom bracket has nuts at the oiter parts, maybe it would make sense to add custom washers to the sides to prevent the sleeve from shifting. An extra mechanical safety layer.

 

[VooteleAer]

Got some "loctite". This is sold by EU webstore. Paid 60€ for it, obviously it's going to return.
That being said, can someone please help me getting the real stuff from USA? I can pay all the expenses...
It seems not to be sold in EU at all, don't know the reason. Maybe it contains some forbidden chemical? Who knows...

 

[MxusMick]

The torque applied to the frame is far more than JB Weld can handle, and the end result of a crash from frame failure would be a concern, in an electric application.IMO