Aluminium to carbon fibre joint adhesive.

Discussion in 'Boat Design' started by Marinetech87, Oct 22, 2014.

  1. Marinetech87
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    Marinetech87 New Member

    Looking for advice on adhesives for carbon fibre to marine aluminium bonding. It is a aluminium flange inserted into a carbon fibre tube to act as a joint on a frame/chassis. All loading conditions are present (tension/compression/torque). Any advice would be appreciated.
     
  2. upchurchmr
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    upchurchmr Senior Member

    The Gougeons suggest wet sanding the aluminum (the wet being 2 part epoxy before it cures), do not wipe off the epoxy, join the graphite to the aluminum.

    This takes all the oxidation/ contamination off the aluminum and allows it to stick.

    The entire direction is in the Gougeon book available as a free download.
     
  3. upchurchmr
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    upchurchmr Senior Member

    Sorry, a duplicate. Probably not worth hearing it twice!
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    Have to be very careful, since graphite eats aluminium.
     
  5. philSweet
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    philSweet Senior Member

    My advice is don't.

    Either mold the flange out of carbon, or use a stock fiberglass flange from the plumbing industry.

    Another possibility is using a GRP epoxy bond layer. This can protect the Al from galvanic corrosion after it is properly etched and chromate primed (illegal to do most anywhere you would be asking this question from), and it has a Coef of thermal expansion about halfway between the two. This could be a decent choice for prototyping stuff. It would be a good idea to get the glass clad Al flanges mfg by an aircraft parts house.

    http://www.boeing.com/commercial/aeromagazine/aero_07/corrosn.html

    <Ad Hoc beat me to it.>
     
  6. rxcomposite
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    rxcomposite Senior Member

    Anodize the aluminum. It has zero electrical resistance.
     
  7. Marinetech87
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    Marinetech87 New Member

    Thanks everyone some great information here.
     
  8. FAST FRED
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    FAST FRED Senior Member

    3M double stick tape , insulates .

    This is used to hold the sides on buildings and in many flat panel attachments , stronger than rivets ,flexes a bit for temperature expansion.
     
  9. rxcomposite
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    rxcomposite Senior Member

    You should also worry about the thermal stress generated by the uneven thermal expansion of two different materials. It can be substantial depending on the mass and the rise in temperature. CF has zero to negative CTe while Aluminum has 13 x 10-6 in/in/oF.

    While it is safe for anodized Aluminum and Eglass combo, we use a thick ply of cross plied Eglass as hard points insert in CF.
     
  10. powerabout
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    powerabout Senior Member

    Like me tons of guys have just epoxied aluminium mast tracks to carbon masts with no issue, hot and cold and lots of bending ( sport boat)
    Cars and glued together these days, for sure there is product made just for that
     
  11. fredrosse
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    fredrosse USACE Steam

    The carbon fibre is in a matrix of epoxy, and the epoxy has a low elastic modulus, meaning to can absorb the differential thermal expansion easily, so it is not usually an issue here.
     
  12. rxcomposite
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    rxcomposite Senior Member

    As I have mentioned, thermal stress can generate enough force to create failure (see example 1 mode of failure). Here is the spreadsheet I have made a long time ago comparing dissimilar materials. For bolted joints, the three mode of failures are analyzed. I have added adhesive bonded simple lap joint. Adhesive can be the epoxy resin used, or any industrial strength adhesive such as Hysol, Araldite, or 3M.

    Note that when bonded, the resin acts as insulating layer to metal. The low modulus of the resin also acts to spread evenly the load over the bonded area. The higher the ratio of (modulus) of the substrate to the adhesive, the greater the efficiency of the bond and is limited only by the shear strength of the adhesive. In low strength application, Sikaflex adhesive sealant will work.

    Note that this is standard textbook reference material for thermal stress and not the sophisticated stress analysis that includes twisting applied load, bulk modulus of adhesives, and safety factors. You need to add the load that will be applied in the inserts plus the safety factor.

    Sorry the figures is in US customary units as the it was sourced from US materials. You may enter new values in yellow cells and change the units to SI. Just be consistent with the units used.

    For commercial use, try to search Click Bond for various fittings/inserts.
     

    Attached Files:

  13. wet feet
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    wet feet Senior Member

    3M 9323 will work,widely used in motorsport for all sorts of bonding.
     
  14. rxcomposite
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    rxcomposite Senior Member

    I made a new spreadsheet. The old one was difficult to manipulate and prone to errors with so many inputs. Non US sytem user also do not appreciate it. The world has not come into agreement what system to use.

    The new one allows to switch from US units to SI base units at the flick of the switch(red cell). You need to input only the materials and dimensions in the yellow cells and the spreadsheet will do the walking on the database. The spreadsheet is protected in the meantime but there is no password. I just protected it while playing around with it.

    wet feet. Yes it seems 9323 has a much higher shear strength than 2216. There are hundreds more of adhesives out there. Maybe I should build up a database.
     

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  15. Marinetech87
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    Marinetech87 New Member

    rx composite that spreadsheet is amazing, thanks so much.
     
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