Carbon Fibre to Aluminium Adhesion

[kadett77]

Hi Guys,

I am looking to attach a carbon fibre roof to an aluminium body and was wondering what would be the best adhesive to use? The roof has to be removed at the end of its life cycle (20 years) relatively quickly. I want to know what adhesive would offer the best structural bond and how or if I could remove the adhesive relatively quick and easily.
Any response greatly appreciated composites and bonding isn't my strangest area.

Thanks

 

[blakmax]

There are two issues you should consider before selecting the adhesive. Firstly, carbon fibers in contact with aluminium will set up a galvanic cell and the aluminium will be corroded. It is possible to prevent this by using glass cloth as the first and last layer to encapsulate the laminate thus preventing contact.

Secondly, as I have posted many times on this site the most important factor in bonding to metals is the surface preparation process. If you don't get that right then it will not matter which adhesive you select, the bond will with absolute certainty fail. The surface must not just be clean. It must be chemically active so that chemical bonds can form between the metal and the adhesive (or primer). The process you use must also generate a resistance to hydration of the oxides on the surface of the metal.

I recommend that you clean the surface with a solvent (MEK or acetone) NOT detergents. Next grit blast the surface to remove the existing oxides and to activate the surface. This must be done just before the next step. You can't do it one day and leave until later. The grit blast is nt to roughen the surface, it is to activate it. Then I would apply a treatment using an organo-functional coupling agent. I strongly recommend that you google AC130. It is a kit which contains the appropriate chemicals for the task.

You may consider using an adhesion primer, but many of these contain hexavalent chromates and are a cancer risk. My epxerience is that if you solvent degrease, grit blast and apply the treatment and then bond in a continuous process without breaks, then the results are adequate without the primer.

Regards

Blakmax

 

[kadett77]

Thanks for the reply Blakmax, really appreciate it.

Yeah I have looked into surface preparation and preventing the galvanic corrosion. My main issue choosing an adhesive which can be removed relatively quickly at end of life (eg 20 years).

 

[blakmax]

If you can remove the adhesive easily then it wasn't bonded properly in the first place. What is the purpose of the addition of the carbon laminate? Is it structural or cosmetic?

 

[1gibson]

So take a torch to the aluminum and burn the bonding agent, then roof can come off. Not fast enough? Use two torches.

Does it have to be at ambient temperature?
Does it have to be removed by mechanical means or could you use heat or chemical?
Is the life cycle for the roof only, or also for the aluminum structure (does the aluminum have to stay intact?)

Is the goal to be able to easily scrap the aluminum?

 

[johnd100]

Hi,

If you add expanding graphite to the adhesive at the EOL you can heat the adhesive to 150 degrees IIRC and the graphite expands and shatters the adhesive. This is one method automotive OEMs are looking into with regards to vehicle disposal at EOL.

John

 

[kadett77]

Thanks for the response guys.
Yeah I'm looking into it due to the new vehicle disposal regulations coming in.
That expanding graphite method sounds perfect John. Definitely going to look into it.

Thanks.

 

[Mrwob]

Hi Kadett77
We use to install carbon roof on steel and Aluminim body of Mercedes Benz for years and The Sikaflex 252 and it works very well. Temp range: - 40°c to 150°c
With a hardness of about 30 shore (depending heat) you can avoid dilatation troubles. I remind you carbon/epoxy resine has no dilatation compare to alu or steel.
Never use hard bonding system.
Like said, apply enough bond to avoid contact with the body. and at least 3mm tick.
Good luke
Steph