Since I have started playing with this stuff I have had my doubts. I decided to test it out.... This was all very crude.

I tested it two ways at 24 hours. The first was a sheer test which I was extremely impressed with.

All metal was 18 gauge with .375"x2.5" glue joint. This is roughly 1 square inch that should hold 3000 lbs.

I used my press to pull them apart. It literally stretched the metal into:


Now my disappointment occurred when I tried to peel the pieces apart. I was able to pull them a part by placing one end in the vise and pulling on the other with vise grips. Once it started it was like peeling a banana. The glue ripped apart leaving some on each piece of metal:




All failures were nearly identical. I did try spot welding and it was a total failure. It does not like heat .

I am kind of disappointed in how easily it pulled apart.

I'm going to give it a few more days to set and try again.

 

I see two potential issues...one, the adhesive has not completely cured; two, there seems to be no tooth on the metal where the adhesive has been applied. I use 3M 08115 and 08116...I have never seen the adhesive split apart like that after it has properly cured. Ambient temperature plays a critical role in cure time, most adhesives will tolerate added temperature from a heat gun to accelerate the cure.

 

They have been at 65 degrees for 24 hours. According to the cure chart they should be pretty close to cured.

All the metal was prepped with a 60 grit roloc.

 

Would be interested to hear your results with a longer cure. What type did you use?

 

3m panel bond 08115

I'm going to pull a few more Monday... I've got five left.

 

Did you dispense the adhesive using the mixing tip?
I have mixed It without using the cartridge gun and mixing tip but care must be taken to get the proper ratio...it is NOT one to one.

 

Yes I used the tip.

I'm not sure that it pulling apart the way it did is an actual failure. It maybe just because the 18 guage​​​​​​ is essientially bending at 90 degrees as I pull on it and putting quite a bit of pressure in a small area. In sheer it ripped the metal into.

I am going to cut some 1"x1" - 1/8" blocks and try pulling them apart.

​

 

Charlie,

Here is something to consider.

I was researching the 3M structural adhesive 07333. It's data sheets show a T-Peel (what I was doing when mine failed) at 1300 psi at 73 degrees at 24 hours.

The 3M 08115 does not have this data and probably the reason it is considered non structural.

Having said that, using my conditions and time frame the 07333 structural adhesive should have been around 700 psi.

If you assume the panel bond to be half that, it would be around 350 psi when I tested them. I'm about 225 and pretty stout, I probably could have mustered close to that. The initial tug was pretty hard but once it started ripping it went easy.

I cranked my shop heat up to 73. I will be interested to see how the others respond in a few days....​​​​
I hope it's strong, As I dang near glued this entire hood together.

 

Sometimes real world testing is better than manufacture specs. I too will be interested in the several day curing time results.

 

Interesting info
My body shop buddy did a similar test years ago. Like you, in shear it stretched and sheared the metal before the panel bond failed. I don't know if he tried peeling it away or not. I'll ask him the next time I see him.

Bobby

 

Folks,
Not sure of the brand? I see a lot of 3M mentioned here. Maybe I missed it? You might try Fusor brand (Lord, now Parker) These adhesive systems have been used in the auto and truck markets for years. And yes the surface prep might be a issue?
Call them they should be able to send you a sample if you describe your application. Worked there for 36 years, its the good stuff!
https://www.lord.com/products-and-so...pair-adhesives
Regards,
Chris

 

It's not a prep/adhesive failure. It is a cohesive failure. Meaning the glue separated from itself.

Again prep work was followed exactly as the manufacturer reccommends.

 

Clintonville,
I understand. Good testing you have done. That's some of the ways that products were tested at LORD too. I am sure there are reasons for that type of failure mode.
Good luck with your panel bonding.
If I was to judge the pictures I would say you got very good adhesion! looks like 90% bond to the substrate. That is very good! That may be the best you can get for that product. The failure mode was through the adhesive. but the bond to the substrate was pretty good. In lab testing they might have recorded the load where the peal strength started to fail? I have no idea what those numbers would be. In the application are you going to be pealing the panels apart?
Regards,
Chris

 

I made a test piece some years ago using 1x.125 strap steel. The overlap on the joint is 1x1 inch. I also applied a glop (technical term) of the adhesive on the top of one of the strips. I used the glop to test by grinding and beating with a hammer...could not break the adhesive nor the bond. Resistance to grinding was comparable to aluminum. I can't say how much force I applied to this piece to attempt to break the bond but it was enough to make a believer out of me.

 

Roughly 72 hours...last 48 or so have been at 73 degrees....

No difference....pulled the metal into on the press. But peeled apart really easy in the vise.

I've attached a picture of what the surface looked like prior to gluing. IF I bend the sample, the glue separates from the metal (adhesion failure).

As long as it is not bent prior to pulling I get a cohesive failure.





This is making me a little nervous. I have split about 6 of these now with identical results. My concern would be if a panel started to peel up for some reason, you could pretty easily rip it off.

Summary so far:

Does GREAT in sheer - metal failure
When welded - adhesion failure
When bent - adhesion failure
When T-peeled - cohesive failure