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Bonding fiberglass to steel - recommendations?


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I need recommendations on what material to use for bonding fiberglass to steel. I'm going to do the body work on my car myself, or at least try to, and need to know what to use for bonding the rear flares on.



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Bonding metal to composites usually fails because there is no mechanical means for the epoxy to interface with the surface of the metal.

Simply put, to fuse any two parts together, there needs to be some sort of material transfer from one to another. This simply cannot happen with respect to epoxies and metal.


One way around this is to encapsulate the metal with the composite material to make a pretty strong "hard point" attachment. Another is to provide some other means for the composite to "grab" onto an hold the part. Things like bolts, screws, metal teeth, etc, attached to the metal and sticking up into the composite materiel provide some amount of grip, but to a lesser extent than the sandwich.


The best method of attachment of composites to metal is direct fasteners...eg. bolt/nuts, rivets.




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I'd go with Rivets, or screws/nutserts if you want it easily removed.


If you must try to bond, as said above, give the material something to grab. Sand down to bare metal, scuff/damage the metal surface as much as possible, and apply your epoxy. I'm pretty sure it still won't hold.


Are you making the flares or buying them?

Edited by Guest
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Keep this in mind

metals- (steel and Aluminum) each have different rates of expansion with heating and cooling .

Composites- glass fiber, kevalar and carbon fiber have a very different rate of expansion and no matter how you bond the two with glue , (bonding agent) they will crack soner or later.

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...Are you making the flares or buying them?


I bought them.

I'd go with a mechanical bond of some kind, or a combination of epoxy and rivets.


Any pictures?

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Here is the most recent pic I have. Fiberglass rear quarter has been trimmed down and attached with rivets (test fitting).



This is the typical response I've gotten on another forum, which is what I'll probably try:


duraglass. we drilled pilot holes through the flares and steel. then put duraglass on both surfaces, then screwed the flare to the car to hold it tight while the duraglass dried. making sure to pack as much as we could in any voids. then take the screws out and it leaves an impressively strong bond.


If you're interested, and have lots of time, my project thread is here:



Crash stuff starts around page 11 or 12, new car build starts at the end of page 16.

My goal is to have it on track in June.

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I've used soemthing similar to patch some canoe outriggers (for sale!). The reaction caused by mixing the two components genterates heat, it's pretty neat.... as long as you know it and don't go poking things to see how well they're setting up. It was kind of a painfull surprise.

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There are several bonding agents made specifically for bonding dis-similar mateirals such as wood to steel, ally to steel, composite to all or steel, etc. The two main products I've used are:





Both can be found at aircraft supply houses, such as Wicks Aircraft or Aircraft Spruce. Wicks is located in Highland IL near St. Louis so shipping is quick and cheap.


The gent who said this usually fails is incorrect. Planes have been built using the above products for, oh the last 60 years and you don't see them falling out of the sky because the wing skins are peeling off!


Glad to hear your shooting for July. Good to see progress being made.



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Don't forget Mighty Puddy!



I wonder how similar that is to gas-tank-patching compound?



I've had good experiences usign aircraft good on cars (oils and metals), but haven't looked into adhesives. I'll have to look into those two recomendations a shot. I've read one reveiw of T88 saying that it doesn't bond to aluminum. I'll be hanging some side skirts soone, I'll be looking for a bonding agent to back up my rivets.

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Well, I've been using T88 to bond aluminum to steel on my various formula cars since 1990.


Hysol is expensive compared to T88. I think it also requires proper ventilation, etc etc. To use T88, I've used simple paint mixing cup (paper, no wax coating), golves and wood mixing sticks. It gets warm but not HOT. Well, I think it's warm, you might think its HOT. The other differences are drying time and fluid resistance. Hysol is more resistant to fuel, oil, etc while T88 dries in 24 hours. Hysol is a 5 day wait for full cure.


It can be fun stuff to play with. Glue your kids bike to the wall? Sure! Heck, glue your kid to the wall!



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