Body panel adhesives

[914helo]

Anybody here used either the Duramix or 3M Automix body panel adhesives? The 3M stuff is more expensive and I think it's probably worth it. All their other products are high quality. Strictly metal to metal bonding. Thanks
Kent

[tat2dphreak]

what are you wanting to "stick" together with glue?

3m adhesives are generally great, but I hope you aren't going to use them when you should be welding?!?!

[lapuwali]

Actually, for many applications, adhesives are much better than welding. It's very difficult to weld thin sheet w/o distortion, which has to be corrected later. Welding heats the base material enough to alter its chemical properties requiring re-heat-treating. Stresses are built-in to assembled parts from the heating and distortions, requiring stress-relieving.

The Lotus Elise is bonded together, as are the majority of the airliners you're likely to fly on these days. I expect you're going to see adhesive bonding become the "normal" way to build a number of structures within a decade or so.

[Brant]

What are some of the other brands of bonding agents out there... ?

are there websites which sell or discuss the properties...?

were building a race car and intended from the beginning to use some of these bonding agents on parts of it... but don't know which ones or how to educate ourselves....

(metal to aluminum primarily)

tia
brant

[BigD9146gt]

Lapuwali, the only problem with your statement is that adhesives have no perpendicular strength (if you get a hold of it and pull apart). Granted on a door skin its ok, because the outer edge of the door is pounded down, creating a hemed seam around the sides, bottom, and sometimes top of the door shell.

With the regards to welding, german steel isn't really high carbon, (not like japanese auto steel which has a higher carbon content, but much thinner so it dents really easy).

What we really need to know is what 914helo is doing.... WELL, what are you doing????

[lapuwali]

I'm afraid your information is out of date. A number of structural adhesives have shear strength of well over 2000psi. 3M AF147, for example, has a shear strength of 2200psi at 300dF, and 5000psi at 75dF. With a sufficient area of overlap and good preparation, this provides plenty of strength. If shear is a really serious concern, then bonding and riveting can be used with structural rivets. The rivets provide the shear strength, and the bond prevents fretting.

However, a number of highly stressed devices rely totally on adhesive bonding. I might remind you that most composite structures are entirely or mostly bonded together with structural epoxies, since they can't be welded. Most front-line open wheel racers are formed mostly from composite structures which don't have a single weld on them, but a great deal of adhesive.

[no substitute]

Yep, as odd as it seems they are indeed gluing cars together, including F1 tubs, I believe. Gluing is being taught to bodymen, of necessity. I inquired on this forum if anyone had glued on any of the chassis re-inforcements available. Folks probably thought I was kidding, but I'm wondering if it wouldn't work. There was some discussion of this over on the 914 Forum. I wish I knew more about how and what to use, too.

[John Kelly]

If the car is steel, and you want to keep all the crumple zone properties intact, weld it. If you don't want to learn to weld properly, and want to use filler to blend in repairs, by all means glue it. I will tell you that in my opinion coming across a glued panel during a restoration would be a pain in the ass. I have heard from reputable sources that a glued patch panel can be a good thing, although I would be concerned about the eventual shrinkage of whatever filler would be needed to hide the seam.

Adhesive may in some instances come to be looked at as filler sometimes is today...a way to cheat that is used more often than it should be. There is nothing superior to welding for joining sheet metal edge to edge for an indistinquishable seam that will react to various forces in much the same way as an original panel without a joint in it.

A dent in a properly welded panel will be just as easy to bump out and metalfinish as an original panel.

For mass production, fast repairs, or work on modern structures that require them, adhesives have their place I'm sure.

You might post on the: www.autobodystore.com message board for some different ideas.

John www.ghiaspecialties.com

[Brant]

John,

I totally trust your advice and value your opinion..

Plus I forgot about autobodystore.. thats a good idea...
In my application I am trying to glue aluminum covers onto a steal chassis... for example where the heater ducts come through the front foot well on a 914.. I'm building a race car and will be required to seal these holes where fuel could potentially enter a cockpit.... I want to use aluminum sheetmetal for weight reasons, and could use rivets but thought that a glue or bonding agent might make a better seal...

I'm not doing body work or even structural work really... just making covers.

brant

[John Kelly]

Hi Brant,

Sounds like a good place for adhesive!

John www.ghiaspecialties.com

[914helo]

Sorry, I should have mentioned in my first post what I was wanted to bond. I wanted to bond a patch on the edge of my steel flare. I had heard about the 3M body panel adhesive (#08115) and wanted to try it. If it works well, then maybe in the future I'd consider using it elsewhere. I'm trying to get all the body work done before prepping for paint. Thanks
Kent

[Scooter311]

I used the 3M 2 part mix when putting the fiberglass flares on mine - I swear you could grab a flare from the edge and lift the car off the ground. Super strong, easy to use, and I think you'd be more likely to damage the panel or the car before pulling it off.
My $.02
Cheerio
Jeff

[BigD9146gt]

Sorry, what i ment to say was that adhesives don't have a high perpendicular? strengh. I'm not sure what the exact term is, so maybe the diagram will help...



In figure 2, adhesives don't hold up as well under those loads as in figure 1. Am i wrong, or has the industry changed everything they knew 1 yr ago?

Granted its neat that F1 cars are just about all glued together, but i'll put money down that civilan cars will not be like that in 10 years, not even 50yrs It costs way to much to convert our industry in that amount of time, and you think repair costs are high now? HAH! Its a nice thought, but deleting steel/aluminum and welding from cars, its not going to happen. Spot welding machines will produce more cars 10 fold over glueing, theres no drying time. ZAP, its done, welded.

[Dave at Pelican Parts]

"Strength in tension" is what you were looking for. Shear is the first diagram, tension is the second one. Compression would be the opposite of tension, where the force is trying to squeeze the panels together.

--DD

[BigD9146gt]

Thanks Dave, it drove me nuts trying to remember.

[lapuwali]

The usual metric given for this is "peel strength", and yes, it's typically 2 orders of magnitude lower than shear strength.

You can't use this stuff exactly as you would use welding. Butt joints, for example, are not going to work well. You have to design joints to be loaded primarily in shear, so they'll never be subject to peel.

Nonetheless, used properly, structural adhesives are starting to be used in much wider applications. Besides the Elise, other manufacturers are looking hard at bonded structures for chassis. Certainly, it's not hard to develop something that will outperform the spot-welded structures commonly built today.

[philinjax]

I have been using 3M products extensively in my body work on the teeners. 3M Scotch-Weld DP-190 is the very best.

I got my 200 pound buddy to jump up and down on the passenger floor pan of a car that had previously had a pan separation from the fire wall and from the longitudinal. I had repaired it with cut out repair strips, DP-190 and SS rivets.
The pan had no reaction to my buddy's stomping and jumping.
It remained solid as a rock.

Phil