Structural panel adhesive

jaybee · February 23, 2019, 06:09:51 PM

More and more late models use structural (or other) panel adhesive in various places. These applications often use rivets at the ends of adhesive runs to prevent peeling, as the product is weak in that failure mode. I realize that OEM-certified repairs can be very specific in their requirements, but is there anything special about these rivets? Or is it a matter of just making sure the fastener is sufficient to prevent the beginning of a peel?

idrivejunk · February 23, 2019, 09:11:58 PM

I always weld. Rivets must be after my time. Thats all I've got, sir.

idrivejunk · February 23, 2019, 10:35:31 PM

To be clear, I weld at the corners of roofs on cars and trucks with gutters on each side, modern unibody style. Which is all the bonding I ever did.

Weld, rivet, bolt, screw... probably won't make much difference but make mine plenty, please. In most cases bonded panels not welded or riveted would probably never move but regulations for collision repair must err to the safest of safe sides. I would at least stick to a guideline of keeping overlapped vertical seams off panel faces, using those only in jambs and maybe on horizontal edge flanges.

Huh, the last post wasn't all I had

but I meant to say corners. Weld corners.

jaybee · February 24, 2019, 02:05:27 PM

Thanks Matt. I had sort of hoped you've have some exposure to this stuff in your collision repair background. I had encountered that welding the corners is common with this stuff. My research into panel bonding adhesives says they have a lot going for them, but they're no substitute for welding. You don't suddenly get to do lap joints in finish panels because they'll have all the same problems as welded lap joints shadowing in changing heat conditions, for example.

There seems to be a lot of adhesives used in new cars now, I figured it's worth learning something about it. They serve as their own seam sealer. They can be used without destroying previously painted surfaces. They're very strong because they provide a continuous bond with plenty of surface area. The one weakness they seem to have is if a joint has an opportunity to be peeled back.

Now I can't find the article where I first saw structural members bonded and riveted. I did find some other material. Here's an instruction sheet for rivet bonding using Fusor. https://www.lord.com/emea/sites/emea/files/RP3022_0.pdf

The aluminum F150 is apparently almost completely put together in this fashion. Here are some interesting shots of how they're put together, and some discussion of ups and downs of repairing such a structure. http://bestride.com/news/what-you-need-to-know-about-auto-body-repairs-on-the-aluminum-2015-ford-f-150

At one time I worked for a company whose fleet consisted almost entirely of Peterbilt 387s. These trucks had a fully composite cab in which the walls, roof, and floor are built in separate pieces. They're all brought together at once and panel bonded together at the same time in a giant jig which uses hydraulics to position the pieces and apply pressure until the adhesive sets.

idrivejunk · February 24, 2019, 02:49:37 PM

I have done very little collision repair in the last decade and am OH SO VERY glad that I followed my heart and pursued classic and custom work even though its a huge pay adjustment. This is why. By the end of 2006, I recall having sent two or three repairs away to dealer operated "certified aluminum repair facilities". I have absolute zero experience with aluminum and just plain zero describes my personal interest in that. If I dealt with it at my job, of course I would generate interest.

The kind of rivets and adhesives obviously matters. Unlike materials matter. I know a close fit matters. Other than that, pfft. Obviously, welding is the more corrosion-prone corner attachment method of properly done riveted vs welded repairs.

Expectations are also relevant though. Insurance paid repairs are not forever work intended to be still good after we are all dead. A completely different set of rules could be applied as opposed to building rod stuff that we may want our grandkids to drive around in or for our kids to race with after us.

After looking at the F150 link (and rejoicing in my career path) the chuckle comes to mind that... if it were all made of steel...

They are right back at prewar body building technique!

jaybee · February 24, 2019, 04:22:29 PM

Very solid points. It touches on dissimilar metals in the F150 article. Steel rivets in an aluminum structure or aluminum rivets in a steel structure are just asking for corrosion failure. The heat of welding and the possibility of collecting water between spot welded flanges hold their own issues. Every car guy knows it and they're the bane of us all.

I liked your last comment. Maybe the next F150 will have ash cores inside the door posts!

enjenjo · February 24, 2019, 06:29:04 PM

Years ago one fleet I worked for had Kenworth trucks, with the cabs assembled with Huck Bolts which are a really high tech rivet. The tool for installing them at that time was more than $20,000. I also worked on a 1961 Peterbilt that had the cab framed out of Ash.

jaybee · February 25, 2019, 08:59:43 PM

Oh yeah, I've seen truck frames with those Huck Bolts. Looks like they ought to be easy to disassemble but NOPE! They're meant to jam together and lock so you can't get them apart.

enjenjo · February 25, 2019, 11:05:59 PM

Quote from: "jaybee"Oh yeah, I've seen truck frames with those Huck Bolts. Looks like they ought to be easy to disassemble but NOPE! They're meant to jam together and lock so you can't get them apart.

For the ones on the frames, I just cut the nut on two sides with a Oxy-Acetylene torch, and pop the remains off with a cold chisel. I did hundreds of them. No scars on the frame either. Yes, I am that good.

For the ones in the cabI used a rivet shaver. Shave them down to about 1/32" and they will pop right off.