Epoxy/MMA in place of welds?

[88911coupe]

Not sure how, but I ended up on some sites related to epoxies and some mentioned MMA adhesives in additions to epoxies, which I'd never heard go. The strength seemed incredible and there were many comments that they were viable alternatives to welding. So...any chance some of these would work on, for example, anti sway bar brackets? I read, somewhere, that adhesives are used in aviation in many applications so it appears there are alternatives to welding.

[rowingone]

According to BladeForums.com, basic welding filler material has a tensile strength of 60,000–70,000 lbs, while JB Weld has a tensile strength of 3500 lbs. However, epoxy adhesives are generally the strongest adhesives in terms of tensile strength. Single component heat curable epoxy adhesives have a tensile strength of 35–41 N/mm˛ (5100–6000 psi).

[dsfnctn]

I have been in the composite industry for at least 40 years building mostly racing sailboats. For success when we rely on a bond with Methacrylate adheasives we will consider that in the design of the build. In our line of building the flange surface has to be increased in order to provide the surface to maxamise the peel strength of the adhesive. I have installed more than a few 1974 RSR rear flares on steel body cars in my days. A great bond is possible as a result of the wide flange of the fenders against the steel body and with the massive curces of the flares with just a bit of fairing compound the flange of the fender is easy to make go away

On the same RSR builds we used relay on a product from Smart Racing that was a modified bracket that was welded in place.

[stownsen914]

Epoxy is strong stuff, but you have to consider the application very carefully. As noted above, the tensile strength of a proper welded joint on steel is much stronger. Properly designed, an epoxy joint can be as strong, but it will probably require a lot more surface area to hold if it's a structural / load-bearing application. Simply replacing a weld with epoxy has the potential to end badly.

[ChrisHamilton]

Methyl methacrylate adhesives have zero place in replacing a weld. None. Epoxy adhesives are used in certain circumstances to supplement bond non stressed exterior panels to a modern unibody. Door skin, quarter panel of some modern vehicles. It would have zero place with a sway bar bracket as it would not have the strength to resist the forces encountered. If epoxy had the strength to replace welds, you could bet the OEM's would be doing it in places. If the OEM's aren't then it's safe to assume there is a reason. Epoxy bonds degrade over time, and heat cycling is one factor in that. Just a bad bad idea.

[88911coupe]

My gut was telling me weld is better...interesting discussion though.

[targa72e]

In the right application "gluing" is used by OEM's. To make it all work takes the right design. Lotus Elise chassis is riveted and glued aluminum.

https://www.youtube.com/watch?v=0ZQXvX_ffXg

But it was designed from the beginning to be built that way. NO WAY I would use epoxy on sway bar mounts.

john

[onboost]

Originally Posted by targa72e

In the right application "gluing" is used by OEM's. To make it all work takes the right design. Lotus Elise chassis is riveted and glued aluminum.

https://www.youtube.com/watch?v=0ZQXvX_ffXg

But it was designed from the beginning to be built that way. NO WAY I would use epoxy on sway bar mounts.

john

This correct.. Modern OEMs (Tesla, Porsche, some Lexus and Ford trucks for instance) with aluminum chassis or tubs have a combination of extruded and stamped components that are glued and riveted in most areas, although welding is required in some structural areas. This is part of the reason why YOU can't buy certain repair parts for these cars unless the shop is certified by the OEM which requires a pretty hefty investment including specific equipment, training, and dedicated aluminum repair area.