Bonding fiberglass to aluminum

shawn

shawn

running dog lackey of the oppressor class
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I need to reattach the aluminum base rail of a camper shell to the fiberglass cap. There's gonna be some vibration, some differential movement, etc.

From what research I've done, it sounds like 3M DP8410NS is the solution. I can get a 45mL cartridge from Amazon for $15. Unfortunately, it needs a $100 applicator system, and I'm not sure 45mL will go far enough to cover the whole ~4 ft long joint. Considering it's just a 2-part acrylic adhesive, maybe I could just squirt it all out onto a piece of cardboard and smear it around like it's JB Weld?

There are other similar acrylic adhesives (Weld Mount 8040, for example), but they seem harder to source. Locktite H8000 looks pretty much like the 3M structural adhesives.

The next best option is regular old 3M 5200. I can buy it at the hardware store for $15, but 3M says you should prime composites with their EC-1945 primer first, and I can't find that anywhere. I might could scuff up the glass side to help with adhesion, though. Honestly, I'm not sure 5200 has the shear strength to keep the joint from shifting, but it should hold the pieces together.

What other options are there?

@Fabrik8
 
This is totally up my street. I love structural adhesives, to a slightly unhealthy degree...

Actually, if you do want something like the DP8410, Lord 200 family or 400 may be a good alternative. The Lord dispenser guns are usually cheaper, and there are generic guns (not branded) that are cheaper and will work with Lord products but NOT 3M products.
The 400 family are impact resistant products, and will have high peel loads.

For some pricing examples, 406 is $16 from McMaster, and mixing gun is $23. I'd maybe start looking in that direction for the amount of bond area you have.

The difference between 403/406/410 is working time. Be careful with selecting a product because of this, especially in summer heat.
 
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Fabrik8 said:
Actually, if you do want something like the DP8410, Lord 200 family or 400 may be a good alternative. The Lord dispenser guns are usually cheaper, and there are generic guns (not branded) that are cheaper and will work with Lord products but NOT 3M products.
The 400 family are impact resistant products, and will have high peel loads.

For some pricing examples, 406 is $16 from McMaster, and mixing gun is $23. I'd maybe start looking in that direction for the amount of bond area you have.

The difference between 403/406/410 is working time. Be careful with selecting a product because of this, especially in summer heat.
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Thanks. I picked it up to expose the joint a bit, and it looks like most all of the original adhesive is stuck to the composite side of the joint. There's no gel coat on this side, but there's also no working room, so it looks like it's going to be a real pain in the ass to get that stuff off. I'll get it set on some saw horses here in a bit and try to get some photos.
 
shawn said:
Thanks. I picked it up to expose the joint a bit, and it looks like most all of the original adhesive is stuck to the composite side of the joint. There's no gel coat on this side, but there's also no working room, so it looks like it's going to be a real pain in the ass to get that stuff off. I'll get it set on some saw horses here in a bit and try to get some photos.
Click to expand...

Makes sense. It's harder to properly prep aluminum, especially if it's not anodized, so that would normally be the failure point for FRP to bare aluminum. FRP is usually really easy to bond to with structural adhesives (much more than bare alum) assuming it's the normal polyester or vinylester resins that are used for products like that.

Hard to say before seeing pictures, but it may be best if you can detach the entire rail along that side to get access.
Any idea what kind of adhesive it was?
 
Pichurs:

1500739691799-1114503253.jpg


1500739761308-456865710.jpg
15007399738311991673846.jpg
 
That bondline looks like shit, no wonder that came apart. It looks like the adhesive took the black paint/finish with it, so the paint to metal bond was the actual failure. Looks like the adhesive wasn't applied in the right place, or at the right thickness, and wasn't clamped properly so there are a lot of voids because it never made good adhesive contact.

What feature of the aluminum extrusion was bonded to? I'm having a hard time figuring out what that profile looks like; the adhesive was in a recessed channel it looks like? That's good for bondline thickness control, so too much adhesive doesn't get squeezed out during clamping/fixturing. You can clamp tight to the aluminum, and still have a proper thickness of adhesive in that recessed channel. Same reason a lot of structural adhesives have glass beads of a certain diameter in them.

If you can get a 2 inch Roloc surface conditioning pad on a right-angle die grinder in there, you should be good to go.

Is that channel (where the adhesive is) really as small as it looks? What is the total height of the face of the extrusion, and what is the width of the channel?

You're going to need a few clamps, and something (wood, whatever) to use as a clamp bar to spread the clamp load across the full length of the joint to get the fiberglass in proper contact with the extrusion during cure.

As shitty as it sounds, if the cap is only 4 ft long you may consider redoing the entire perimeter properly. Unless this happened because of an impact on that one side, in which case the other side may not fail anytime soon...
 
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Fabrik8 said:
Is that channel (where the adhesive is) really as small as it looks? What is the total height of the face of the extrusion, and what is the width of the channel?

You're going to need a few clamps, and something (wood, whatever) to use as a clamp bar to spread the clamp load across the full length of the joint to get the fiberglass in proper contact with the extrusion during cure.

As shitty as it sounds, if the cap is only 4 ft long you may consider redoing the entire perimeter properly. Unless this happened because of an impact on that one side, in which case the other side may not fail anytime soon...
Click to expand...

The bond area is about 3/4" high. The recess is 1/4" high x about 1/16" deep.

The cap is 8ft long, but broke loose over about 6ft of the length. Only about 4ft of that is accessible, so that's the part I'm working on re-adhering. It came out of a junkyard, so likely failed due to an impact on that corner that deformed the bed.
 
Well, get to whatever you can with proper prep and adhesive, and run a bead of caulk or seam sealer over the entire rail after that to seal the part in the middle that you can't get to. Should be fine.
 
I said "fuck it". I'm going to the boat store to buy a tube of quick-set 5200. It'll stick. Probably for a while, maybe forever. If it doesn't, I can redo it later. But I get to use the shell next weekend, which isn't an option with any of the other adhesives I've looked at over the last couple of days.

<shrug>

Thanks for all of the suggestions, though. I'll probably need them sooner or later.
 
shawn said:
I said "fuck it". I'm going to the boat store to buy a tube of quick-set 5200. It'll stick. Probably for a while, maybe forever. If it doesn't, I can redo it later. But I get to use the shell next weekend, which isn't an option with any of the other adhesives I've looked at over the last couple of days.

<shrug>

Thanks for all of the suggestions, though. I'll probably need them sooner or later.
Click to expand...
You kinda went all Fuller on that advice didn't ya. I.E. cheap, quick and whatever is within reach. LOL
 
shawn said:
I said "fuck it". I'm going to the boat store to buy a tube of quick-set 5200. It'll stick. Probably for a while, maybe forever. If it doesn't, I can redo it later. But I get to use the shell next weekend, which isn't an option with any of the other adhesives I've looked at over the last couple of days.

<shrug>

Thanks for all of the suggestions, though. I'll probably need them sooner or later.
Click to expand...

Once you use 5200, that's it. You're never going to want to remove it, so you better hope it works. It might though, so give it a shot. It's a really good sealant, so that's a bonus.
 
obullfish said:
You kinda went all Fuller on that advice didn't ya. I.E. cheap, quick and whatever is within reach. LOL
Click to expand...
Haha, beat me to it. Typical "hay u guyz wuts təh rite weigh?" Followed by intelligent advice and then a complete ignoring of such advice.
 
jeepinmatt said:
Haha, beat me to it. Typical "hay u guyz wuts təh rite weigh?" Followed by intelligent advice and then a complete ignoring of such advice.
Click to expand...

<shrug>

If I could have ordered the Lowe stuff from Amazon and had it here on Tuesday, I would have gone that route. But I wasn't spending $150 on the 3M stuff to fix a junkyard canopy.

I suspect they used 5200 (or something like it), to adhere it the first time. It'll come off with a 3M scotchbrite pad, either way.
 
shawn said:
I said "fuck it". I'm going to the boat store to buy a tube of quick-set 5200. It'll stick. Probably for a while, maybe forever. If it doesn't, I can redo it later. But I get to use the shell next weekend, which isn't an option with any of the other adhesives I've looked at over the last couple of days.

<shrug>

Thanks for all of the suggestions, though. I'll probably need them sooner or later.
Click to expand...
How did this end up working for you? I'm thinking about doing the same on an old topper.
 
Yes! - I'm going to the same for mine. Cleaned it up as discussed above and then 5200, a piece of wood, and some clamps?
 
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