Crankshaft
Apr 21st, 03, 10:47 PM
I did some research on 3M 8115 and here's what I've got so far.
It's a 2-part epoxy made for bonding steel, aluminum, SMC, and fiberglass. It says it is heat curable, but does not list how much heat and for how long. This can become an issue if you are heating near painted surfaces. It also makes no claim to the strength and elongation difference after heat curing (one reason to not want to use on class A or visible surfaces).
It does state it is not good for read-through or "ghost lines", and I imagine the strength and elongation are the culprit.
This product also states it is non-structural, meaning it isn't recommended for unibody cars where the body is part of the load carrying structure; you can use it on fully framed cars.
It also has low peel strength. It states to spotweld at the points where you would see peel forces.
After looking at the "lapshear" (misnomer, since it does not actually measure any sort of shear forces) and impact data, I'm not real impressed.
The lapshear data does not tell me modulus or %elongation; just a load value (big deal; several different adhesives can generate the same number, but it doesn't tell me if it's right for the application.
The impact data was carried out at 82°C. Most things will do reasonably well at higher temps; it the lower temps you need to worry about, and these were conspicously absent.
They claimed great corrosion protection and in a comparison againts Lord Fusor, they were superior. No types of corrosion tests and dat were actually listed.
Now.....
I will get some of this adhesive and run corrosion testing (salt water chamber, 100°C at 100% humidity, brake fluid, etc.)if this is what you want to see.
Based on what I saw of this product so far, a structural urethane could probably do just as well.
Ghost lines can be lessened by joint design.
When you flange a panel to create an overlap, you are putting stress at those two bends in the flange. Then, when you put in an adhesive that may have a tendency to shrink, it places a non-uniform stress there. A few days out in the sun, then into cool shade, and here come the ghost lines!
One way to create a less stressful joint is to separate the flange. Basically, fit the panel so it would be butted against the other. Now, have a strip of the same gauge metal (or slightly thinner) with a wide overlap (2" or more) and place it so it covers the butt from behind (kind of like drywall taping).
Now I know this may not be feasible on certain things, but it may be useful for others. You don't even have to do it all at once. You could cut out a section of panel, bond the strip to the inner side of the hole where the panel will go; let it cure up for a while (cleaning off any squeeze-out where you will be bonding the other side to). Now you have just recreated your flange, but with reduced stress. now glue in the rest of the panel. Refinish as normal.
For an application like this, an adhesive with low shrink and reasonable elongation (10-12%) would work.
In talking with some of our metal bonding guys, they say most aftermarket stuff is not all that good in the first place. The reason is this; to develop this type of adhesive takes several man-years and millions; the market for it is just not there to make that type of investment, so you get what is out there now.
Now, there are lots of adhesives out there, and some will perform better than others in certain aspects. Application is the real key here.
Crankshaft
It's a 2-part epoxy made for bonding steel, aluminum, SMC, and fiberglass. It says it is heat curable, but does not list how much heat and for how long. This can become an issue if you are heating near painted surfaces. It also makes no claim to the strength and elongation difference after heat curing (one reason to not want to use on class A or visible surfaces).
It does state it is not good for read-through or "ghost lines", and I imagine the strength and elongation are the culprit.
This product also states it is non-structural, meaning it isn't recommended for unibody cars where the body is part of the load carrying structure; you can use it on fully framed cars.
It also has low peel strength. It states to spotweld at the points where you would see peel forces.
After looking at the "lapshear" (misnomer, since it does not actually measure any sort of shear forces) and impact data, I'm not real impressed.
The lapshear data does not tell me modulus or %elongation; just a load value (big deal; several different adhesives can generate the same number, but it doesn't tell me if it's right for the application.
The impact data was carried out at 82°C. Most things will do reasonably well at higher temps; it the lower temps you need to worry about, and these were conspicously absent.
They claimed great corrosion protection and in a comparison againts Lord Fusor, they were superior. No types of corrosion tests and dat were actually listed.
Now.....
I will get some of this adhesive and run corrosion testing (salt water chamber, 100°C at 100% humidity, brake fluid, etc.)if this is what you want to see.
Based on what I saw of this product so far, a structural urethane could probably do just as well.
Ghost lines can be lessened by joint design.
When you flange a panel to create an overlap, you are putting stress at those two bends in the flange. Then, when you put in an adhesive that may have a tendency to shrink, it places a non-uniform stress there. A few days out in the sun, then into cool shade, and here come the ghost lines!
One way to create a less stressful joint is to separate the flange. Basically, fit the panel so it would be butted against the other. Now, have a strip of the same gauge metal (or slightly thinner) with a wide overlap (2" or more) and place it so it covers the butt from behind (kind of like drywall taping).
Now I know this may not be feasible on certain things, but it may be useful for others. You don't even have to do it all at once. You could cut out a section of panel, bond the strip to the inner side of the hole where the panel will go; let it cure up for a while (cleaning off any squeeze-out where you will be bonding the other side to). Now you have just recreated your flange, but with reduced stress. now glue in the rest of the panel. Refinish as normal.
For an application like this, an adhesive with low shrink and reasonable elongation (10-12%) would work.
In talking with some of our metal bonding guys, they say most aftermarket stuff is not all that good in the first place. The reason is this; to develop this type of adhesive takes several man-years and millions; the market for it is just not there to make that type of investment, so you get what is out there now.
Now, there are lots of adhesives out there, and some will perform better than others in certain aspects. Application is the real key here.
Crankshaft