Gluing body panels, Is this ridiculously stupid idea? Options

[mikea100]

I recently caught “Speedmakers” on Speed channel. It showed Aston Martin factory and how they glue body panels, they went on to say that it creates stronger bond than welding. Has anybody tried gluing any panels. I was thinking about using some high strength epoxy and gluing Engman inner long kit, it seems as a good candidate as the pieces are flat and fit flush. What do you guys think?

[Jeff Hail]

I’ve been doing this gig for a long long time.

1) Bonding non structural panels is an acceptable practice.
2) Bonding structural components like steel rails is not. Composite tubs are another animal. Manufacturers such as Mercedes bond composite trunk floors to steel sub-structures on almost every new model now.
3) A lot of manufacturers use a process called weld-bonding. Adhesive augments the weld strength. This is where a weld such as a plug, resistance or laser weld is done through the bonding material. Very common on center pillars, rockers, unisides and floors. See a lot on aluminum based chassis's.

Bonding performs very well in shear. Excellent fatigue resistance due to a larger load spread throughout the mated components. High viscoelasticity.

The downside of structural bonding is low peel strength with components that are out of plane. Large panel gaps tend to be problematic versus tight fitting joints. Joint strength is dependent on surface area bonded.

ALCAN has done extensive research with welding and bonding of aluminum. The process of weld bonding aluminum came about because the metal to metal welds or through welds acted as clamps or tacks while the adhesive cured. The metal welds also increased peel strength dramatically. Bonds also reduce oxidation at weld sites. Resistance welding of aluminum has a high tendency to crack at weld locations. Welds combined with bonding average a 23% increase in the force displacement curve.

Most of the auto manufacturers use a product called Betamate 4601 in the manufacturing/ bonding process. It is a single part adhesive. When the aluminum BMW 5 series vehicles are manufactured or repaired the recommended cure cycle is 175 degrees for 30 minutes. The only way you can get that is with a heated spray booth or flame.

For the 914:
When I installed the rear trunk floor I weld-bonded three sides at the Trans cross member and wheelhouses. Why? I was experimenting with Wurth's Power Bond. The electric welds were enough. I just did it anyways.

Would I bond the Engman Kit? I would not bond alone because those longs flex, bend and twist. I would definitely supplement the welds with bonding though.