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Old 09-28-2008, 12:07 AM
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Follow up peel test from my sons science project on welds vs glue.

Well, today I did my "peel test" on the panels I have been storing in my tool box for a number of weeks.

I have to tell you, it yielded some very interesting results. First off, you may remember when my son did a similar test for a science project a year or two ago in school. You can view the test that I posted on my sites including here at Welding or Bolting vs gluing panels on, a science project...

Now, the second I posted that test I got people saying all kinds of things like a "peel" test would fail, and I thought it would as well, but that isn't what the test about. I wanted to go further, so this test did just that. Another thing people said was about the "surface area" of the bonding and how it was "unfair" to compare it to the smaller surface area of the welds. Again, how about we make it fair and don't plug in the welder as the glue gun used no electricity or heat?

The test tested what it tested, nothing more, nothing less.

So, months ago I cut some coupons up to do this test. I bent them, and over the months I spot welded one, plug welded another and bead welded another. I bolted the last one together. I then bonded them using the same procedures my son had used on the last test, going by the instructions that came with the adhesive.

I clamped the pieces in the frame machine pulling from both directions just as before. The first one was the plug weld, it pulled pretty taut with a lot of pressure on it until the welds failed..WHAM with the clamps flying apart. I couldn't believe that the glue was going to win again. The next one I did was the spot weld, again, it pulled pretty taut, WHAM the glue failed this time.

The next was the bolted panels. Now, this was the one that gave the glue in the last test the most fight. I was setting the thing up and had my boy hit the switch to pull the chains taut, but no pressure at all on them. Just starting so the thing wasn't laying on the rack. The damn adhesive broke before the test began! I couldn't believe it, the darn bond looked like it wasn't even stuck to the metal! It looked ground clean just as it did before the bonding!

So, I pulled that stuff off the clamps and tried the last one, the weld bead. It won over the adhesive, a little more pressure was needed but not nearly as much as the spot weld and the plug weld.

So, after following the instructions to a tee, or so I thought, two failed while the others held pretty good, one winning over welds.

I don't know what to think other than I screwed up some how, maybe clamped them too tight? Maybe I didn't blow off the dust being I was doing this in a couple of extra minutes out in the garage and probably had a ball game starting that I was rushing to.

Anyway, they broke so clean without so much as a tiny bending of the metal. I will be re-bonding them and giving it another test.

You know the funny part, the only thing I know that I did different was that I spread the adhesive onto the metal after laying a bead with a bondo spreader just as the instructions say. I have never done this, always using an disposable acid brush. I know this is ludicrous to think it could make a difference but that was all that I KNOW I did different.

Brian


All the coupons welded, bolted and bonded together.

Being pulled on the frame rack.

Plug welded with the MIG

Spot welded with a Pro-Spot

The glue that failed before the test even began with the bolted panels.

The end results.

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Old 09-28-2008, 03:59 AM
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Thanks for the thread. Which adhesive do you use? I thought panel-bonding adhesives are usually applied to Epoxy-primered Metal?
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Old 09-28-2008, 05:50 AM
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Thanks for the update, I remember that thread well. I would be very interested if you included a good epoxy in your next test (west System maybe?).

One thing that might have affected the adhesive test is the cleaner. I know you are not a fan of acetone as a cleaner but I have been using epoxy and adhesives in boat maintenance/restoration for years all over the world and have never seen anyone use anything else when dealing with the raw material i.e. plain,bare wood and metal. I would be interested to see if that made a difference. (Although it is not often we use epoxy on its' own to bond bare metal, it is usually combined with a fastener. )
Thanks for taking the time to post your results.

(One of the most popular adhesives in the marine ind. is 3M's 5200 it is extremely aggresive and bonds well to almost anything.)

Last edited by scrimshaw; 09-28-2008 at 06:20 AM.
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Old 09-28-2008, 07:50 AM
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notes on 5200.....

Hi Scrimshaw,youre correct,5200 is great,the only problem is that it takes a week or more to fully cure. BUT,once cured,you cant pull whatever you used the 5200 for,apart.
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Old 09-28-2008, 07:52 AM
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This adhesive is distributed thru Winzer. I didn't apply an epoxy first, because that is in the tech sheet. As far as cleaning, the metal was ground and the adhesive was applied within a minute or so. The metal was spotlessly clean as far as corrosion or anything like that. The only thing I am thinking is I didn't blow it off well and there was grinding dust on the surface.

Brian
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Old 09-28-2008, 08:10 AM
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Questions, as stuff don't look right from pictures.

I have a little knowledge here as I was involved in the original testing of this for tec-cor, Allstate and the Canada insurance funded tests back in early 90's.

First you never plug glue.
Second each glue has ex-mils for thickness that must be met for maximum bonding strengths.
Some do this by glass beads built in and then some like Duramix don't need them as one mil is enough for maximum strength, every product is different and application is important as well as working times that will affect the lap shear. Prep of metal is just as important, down to grit of grinder.

Also you cannot use bumper repair to a bonding test, it needs to be the actual bonding adhesive and only reason I bring this up is I'm not familiar with a clear metal bonder, could be something new but i have never seen one except for fiber glass.

If this is just another BS madeup test, just let me know and I will let you have your ego fun and stay out of it.

Original test, results were over 212 lbs of written papers.
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Old 09-28-2008, 08:48 AM
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Thanks Barry for your REAL knowledge your post was going very good until your "another BS test", but you almost got there! Good for you

The bonding used is Winzer 891.0125 Panel Bonding Adhesive 50.

It was the same bonding used in the previous test that my son did. If you click on the link the bonding survived over the welding, spot, bead and bolts with flying colors. That test by the way was a "Lap sheer" this one was a "Peel" test.

These test coupons were set up, not under flawless conditions but more as the product would be used in the field.

And without a doubt, there was some "application error" in my opinion. I DO believe I did something wrong to make the bond fail as bad as it did on the bolt and bead weld test strips. It held on MUCH better on the other two test strips. The failure gotten on the spot welds made total sense and "felt" right. The failure on the plug welds, that makes total sense as well being the metal is heated much more and it failed right at the metal surrounding the weld.

Where the bond simply fell apart, I have to attribute it to "pilot error" in some way.

Using the directions the panels where "firmly clamped" in place. I believe this particular product has the glass beads to insure proper mil thickness. I have to assume that being the instructions "Firlmy Clamped".

I didn't weld thru any of the bonding. The test was set up as follows....

If you look at each test subject, they are made up of three metal coupons. They are in the same order laying there on the ground in the top photo as they are in the bottom photo (this was not planned, but I am glad it ended up that way). Each test strip was made up of three sheet metal coupons, all of the same gauge (I don't know what it is but I could measure that, it's about 20). On coupon has a 45 degree bend on each end. Then two had a 45 degree bend on only one end.

The first one tested was the plug welded one. It is on the top of the bottom photo and to the left of the top photo. I had one of the coupons with the 45 degree angle plug welded (using 1/4" holes punch in it) to a piece with both ends bent up at a 45 degree angle. I then to the other end of that piece which was now plug welded to the first piece and bonded it at that 45 degree bend to another piece with only one bend. This three coupon test strip was then put on the frame machine with the single folded coupon that was plug welded attached to a pulling clamp hooked to one of the pulling posts. The other end of the three coupon strip was attached to a clamp hooked to another pulling post. Both pulling posts were on so when I hit the button both pulled ripping the three coupon test strip in half. Result being (in theory) the weakest joint would fail first.

So, each three coupon test strip had one end bonded with glue ONLY. Then the other end had either plug welds, spot welds (using a Squeeze Type Resistance Spot Welder "STRSW") one bolted with 1/4" bolts and one with a mig weld bead down the seam.

Brian
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Old 09-28-2008, 09:17 AM
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And by the way, I want to make this clear to everyone. I was afraid posting this would cause some concerns in users. Listen, even if this test shows that the bond filed over the welds it is ONLY a test and it is the Mythbusters style "FAIL BE DAMNED". Everyone whom I chatted with after the first test agreed the bond would probably loose in a "PEEL" test. So it loosing now is no surprise. HOWEVER, I do believe there was some pilot error on my part to make the failure as it is in this test. I think the bonding should put up a better fight than I got, but I EXPECT it to fail under THESE test conditions.

If you go to the link to the original test that my son did it WHIPPED *** and took names up against the welds.

Brian
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Old 09-28-2008, 09:33 AM
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Quote:
Originally Posted by BarryK
First you never plug glue.
Second each glue has ex-mils for thickness that must be met for maximum bonding strengths.
Some do this by glass beads built in and then some like Duramix don't need them as one mil is enough for maximum strength, every product is different and application is important as well as working times that will affect the lap shear. Prep of metal is just as important, down to grit of grinder.

My understanding of the minimum required thickness is that it has less to do with the bonding,(adhesive), properties of the glue, but the thickness required depends alot upon the movement expected in the joint, and the elongation properties of the adhesive to accommodate that movement in order to prevent a structural failure of the adhesive itself, (cohesive failure). A minimum thickness is also required to allow the shrinkage of the adhesive during curing to prevent pulling itself away from the substrate before attaining maximum strength or separating within itself..

I don't think the metal was prepped right in Brian's test. Or the glue itself has issues. There is no evidence of any cohesive failure at all, which leads me to believe that the glue failed to bond at all.


In working with various glues and epoxies intended for use with our materials, we found that just clamping the parts together lightly got the best results..We never clamped any tighter once the excess glue stopped squeezing out of the joint.

In our shop tests at the fiberglass shop we did test coupons using our standard prep and clamping methods, waited at least 3 times the recommended full strength cure time.and then used various means to pull or break the bond...We considered the glue acceptable if we had a substrate failure, or a combination of substrate and cohesive failures, but adhesive pulling away clean from the substrate or cohesive failure alone was a cause for failure of the test, and that adhesive was no longer considered.


Our tests used various epoxies and marine adhesives to glue wood, steel, and fiberglass to fiberglass We also did some steel to steel tests, but as we did not usually glue steel to steel, it was for educational purposes only.. We did lapshear and peel tests as well as flexing tests, none of them were very scientific and did not strictly conform to any ASTM tests, but they showed us what we needed to know. (we had no frame machine, so we would chain the test subjects to the forklift mast at one end, and the forks at the other...Forklift won every time...)

We deliberately chose to do the minimal amount of prep, as this would be the usual case in the rushed and dusty environment of the production assembly department. Sometimes production parts were prepped to be bonded days or weeks in advance, and prior to bonding we needed to be able to do just a minimum of prep, usually a blowgun sweeping, then wipe with acetone, then bond the parts.


An epoxy made by a company called Resin Formulators worked very well, but it became so hard to find that we discontinued its use. We since tested and started to use epoxy made by a company called Plexus.


My point to all of that is that a test procedure doesn't need to have a ton of science and documentation behind it in order to get usable results. I remember repairing parts glued with the old marine polyester adhesives (reid's adhesive got used alot in our shop), that failed for one reason or another, but have yet to see a part comeback with failed epoxy.

We did this testing back in the mid eighties, I still talk to the owner of that company, and would hear about any comebacks.


Later, mikey
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Old 09-28-2008, 01:23 PM
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Miky,
Glad you know how to use that particular brand, not sure what you are using it on but I'm sure its made to work for whatever it is.

Now to make a blanket statement how all should be use will not work, there are well over 300 static type manufacturers around and every product is different, be it polysulfide, epoxy, acrylic or polyurethane and God knows what else.

We are talking METAL BONDING HERE, not PP, UR, PE,TPO,TEO fiberglass or SMC and the major players in this market have their own ways of prepping, applying and clamping.
Some want the clamp as tight as if you are going to weld.
Some want spot welds in certain parts of panel.
Some want the adhesive applied to both sides of metal before putting together instead of just one bead and for good reason.

This is not something you screw around with if bonding a roof skin or what ever, the manufacturer knows best.

Elongation and shore rating perhaps could be why the the big players have so many different products with different shore ratings and dry times.

If any of you out there try a bonding agent follow the "manufacturers recommendation" from start to finish, period.
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Old 09-28-2008, 02:07 PM
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My point to that post was not to endorse a certain product, but to illustrate that field testing the material that a manufacturer reccomends on your particular application is a necessity. Even if only to familiarze yourself with the material.

People get sold materials all the time that don't work for one reason or another. Understanding the cause of failure by using common sense, knowledge of the characteristics of the material itself and observation can only help the manufacturer get you the right material.

The adhesive that Brian used was obviously intended for gluing steel to steel, (I can't believe that he'd do a test with just any old glue that was laying around...not like him at all), so why did it fail? A review of the tech sheet and some more testing is in order to properly answer that.

Every time I needed a material to do a certain job, after discussion with the manufacturer, we were sent samples to do our own testing with, and an instruction sheet on proper use. It was expected of us to perform our own suitability tests, which I feel is a better way to go than just buying something and putting it to use just because "the manufacturer said it would work."




Later, mikey
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Old 09-28-2008, 07:09 PM
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I think the biggest reason it failed was I was asking it to do MUCH more than it was designed to do! Like I said, the lap test provided totally different results, why, because that is the manor in which it is designed to be used.

I have to tell you, this is how anal I am at following the directions. I had planned on doing this a number of times but found that the temp wasn't going to be in the recommended area for the complete cure, I put it off to another day. This is one of the reasons it went undone for so long. Second, I went do bond it a couple of weeks ago, got out my little angle die grinder, found that all I had was 50 grit discs and the tech sheets says use 36 Grit (in bold bring on the sheet), so it was put off for another few days until I found my self with the nice new 36 grit discs.

I can not make it clear enough, I ABUSED this product, that is the biggest reason why it failed.

Brian
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Old 09-28-2008, 11:54 PM
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Quote:
Originally Posted by powerrodsmike
(we had no frame machine, so we would chain the test subjects to the forklift mast at one end, and the forks at the other...Forklift won every time...)
Was the forklift also chained? If not, you admit cheating. Try that again with the test subjects unchained or the forklift chained and see who wins! I can't believe you'd declare the victor in the same sentence in which you reveal how the contest was rigged. I'd bet that the test subjects weren't even allowed to use hydraulic cylinders.

It was an unfair contest and therefore must be unscientific. You will have to run it again, under fair conditions, before making a valid, supportable choice between glue or forklifts for holding fiberglass to wood, steel or fiberglass. Sorry.
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Old 09-29-2008, 01:06 AM
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Quote:
Originally Posted by grouch
Was the forklift also chained? If not, you admit cheating. Try that again with the test subjects unchained or the forklift chained and see who wins! I can't believe you'd declare the victor in the same sentence in which you reveal how the contest was rigged. I'd bet that the test subjects weren't even allowed to use hydraulic cylinders.

It was an unfair contest and therefore must be unscientific. You will have to run it again, under fair conditions, before making a valid, supportable choice between glue or forklifts for holding fiberglass to wood, steel or fiberglass. Sorry.

We did ask the glue if it wanted some hydraulic cylinders of it's own, just to keep it even, it declined,(typical of the glues I've tested, always trying to show off. I'm sure it was sniffing itself before the contest)

Mikey..
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Old 09-29-2008, 08:23 AM
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I have found most glues to be arrogant bastards. But this Winzer adhesive I used is pretty cool, the kind of glue you want to go out and have a beer with. And I mean that in a heterosexual man to glue way.

Brian
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