As I advance my skill I’m having a lot of new questions. My main one which I can not figure out is this and how to design my one off part.
I’m looking at making a carbon plenum that’s bonded to aluminum. I figure the base that bolts to the heads will be cnc’d aluminum and the runners carbon and the box carbon also.
One of my main questions is how would I bond the carbon runners to the aluminum? I’ve seen pictures on the internet where it looks as if the carbon goes inside the aluminum. I’m looking for a very strong bond too since for this application it would see 20lbs of boost also.
Something like this I’m looking to make but I’m having a very hard time imagining how I’ll bond everything.
This is done with telescope truss poles all the time, that are in tension/compression. The aluminum end either goes inside, or slides outside of the CF tube. Your bond strength will be related to how much overlap you have of the 2 parts.
This would be built with a bonding jig an you glue a part and builds as you go
Some parts will be pre bonded so you have a sub assembly that goes into the main assembly
Some parts could be bonded with film glue during the initial cook of the carbon part
Wouldn’t use 490,that’s not even as good as 3m9323
Making a similar thing for a f1 car at the moment but there’s lots more carbon in that
All bonding is hysol 9394 good till 180 deg and VERY. good bond characteristic
Everyone thank you for your replies. You’re all huge help!
F1rob I will go with your recommendation when it’s time and use the hysol.
I now have to design the runners and the plenum area. And figure out how I will attach the trumpets.
Here are my thoughts.
Get the bases cnc’d out of aluminum.
Make the runners individually.
Where the trumpets are inside the plenum themselves I think I can use a sandwich method with screws potentially? I can get them machined and have one portion inside the plenum and the other outside with a flange. It would also give me room to cut the holes in the plenum and give some room for error since the flange would fill any large type of gap.
The flange where the throttle body I haven’t though about but that could be built into the mold design potentially.
If I do slip fit joints with the carbon either on the inside or outside of the aluminum it attaches do you think the adhesive will hold it? I’m worried that it won’t. I guess when we also start thinking about angles and such there may be a way to design things where they fit together but when coming apart it will be more difficult. It’s hard for me to explain but it wouldn’t be just a straight pulling out motion since there’s some angles and such.
I’m real excited to try this out but it’s such a huge task. I have to figure out how to make the runners to exact tolerances so maybe the lost wax method or some dissolvable foam or bladder mold.
Then I have to figure out how to make the plenum and make it smooth inside.
Some very interesting research, I just came across. Basically, they state that surface roughness when bonding doesn’t matter much. “Keying”, adding mechanical grip, etc is not paramount in bonding. They go on to explain that the bonding happens in a very thin molecular layer. The molecules of the parts have to be freshly exposed, energetic and ready to react with the adhesive. The level of this readiness and energy is called Surface Energy and it can be tested and measured. They found that the Surface Energy decreases fast by not only contaminants but also just exposure to the surrounding air as the molecules react and settle down.
In practical terms they say: prep and bond right away. Prep can be sanding, blasting, plasma, etc. For most of us it would be sanding so the practical advice was to sand, then solvent wipe before and after wiping - as the sanding can move grease and other contaminants into the surface.
More here:
One hour webinar: http://btglabs.com/video/webinar-mea…ed-interfaces/
Paper on sanding and solvent wiping: http://btglabs.com/papers/investigat…urface-energy/
Nicely explained by a naval architect here: https://www.graingerdesigns.net/the-lab/secondary-bonding-in-perspective/
I never have much luck bonding cf to aluminum unless there is a mechanical lock. For example, I have had success wrapping an aluminum threaded insert with carbon fiber yarn.
I am still trying to find a way of bonding a flat aluminum surface to a flat cf one. Let us know if you figure it out. I am sure plenty of people will have a use for such knowledge if you come up with a reliable method.
The other way that work is using aluminum clamps on cf tubes but that’s not technically bonding.
we bond carbon to aluminum all the time, works like a charm.
bond prep is the key. You can also use bond promoter like C-130, which helps significantly. If you use a hysol structural adhesive, it will be a super strong bond. This is what holds the ribs together in a wing or spar, so it would have very high load handling capability with the right surface area. The other thing to think about is bond gap, you don’t need a perfect fit, nor do you want it as adhesives require a bond gap to give a good bond. Some adhesives also have glass beads to achieve this bond gap.
one concern though when bonding dissimilar materials is the possibility of galvanic corrosion… this may or may not be an issue? If it is, then you will need to either prep the bond area with a coating. The C-130 might help? Or else use fiberglass as the outer ply of your laminate to insulate the carbon/aluminum contact.
All in all this should be pretty straight forward. You may need jigs and such if you want to repeat the process.
I have used this method for a long time now for driveshaft ends.
Alloy inserts bonded into CF tubes and exposed to high torque loads.
Clean surfaces.
Abrade surfaces.
Clean again.
Apply thin layer of structural adhesive.
Key alloy again through adhesive with coarse paper- 40-60 grit.
Wipe off excess.
Apply fresh adhesive to both surfaces and bond.
Allow to cure.
Post cure.
Theory is:
You are abrading the alloy through the resin which seals it from the air.
Thus preventing any chance of oxidisation.
This works very well with bonding epoxy to Lead too.
Would using C-130 allow a strong bond between a flat aluminum surface and a flat cf part? That’s the one that always caused me issues. Tube inserts are not usually an issue for me. It’s where there is no mechanical lock to hold it in place.
I’m intrigued to try C-130 to see if it will solve my issue now.
What adhesive are you using Zebra? Carbon and aluminium is easy, but you need to be using a suitable adhesive. Generally epoxies work the best, so something like Huntsman Araldite 2015 will work perfectly assuming your prep is good, you’ll break the laminate before you break the bond. Whereas a PU adhesive like Araldite 2018 wouldn’t be very good at all, even with proper prep. There will be lots of good adhesives, but I know the Huntsman range quite well and use them myself, so it’s just a matter of looking at the data sheets and application guides.
It sort of sounds like you are trying to bond the ali using regular laminating resin, which while it can work, it isn’t really ideal. A good bond needs a good bond gap, which means having an adhesive that stays where you put it. Laminating resin, even higher viscosity ones, are simply too thin and will likely leave the bond area on the dry side unless you have a way to lock it in place, as you mentioned.
Adhesion promoters are largely unnecessary for most applications unless it has been spec’d into the engineering. Unless you’re building aircraft for Boeing, you won’t need it if you pick the right adhesive.
You must deoxidize the aluminum before applying the pre-treatment and the primer that is included in the AC-130 kit. The aluminum oxide layer is the number one reason why bonds to aluminum fail. As for adhesive, Hanaldo gives great advise, though I believe that laminating resin will work just fine as long as you use something like microspheres for bond line spacing.
Yes nothing wrong with thickening up laminating resin with microballoons, fumed silica, calcium carbonate etc. That’s essentially all a toughened adhesive is really, so there’s definitely nothing wrong with that.
But without any fillers, a laminating resin is just too thin to be reliable.
It’s epoxies that I have had issues with for bonding to aluminum but I never considered trying one of my thick epoxy resins as a solution. I have a number of thick resins on my shelf so trying one is an easy for me. I guess I avoided using them for bonding because they aren’t always the best for achieving a flat surface.
I sand the aluminum immediately before bonding to remove the aluminum oxide layer. I haven’t tried a chemical remover but it sounds like a good idea. Sanding hasn’t proved to be a reliable method for large flat surfaces.
I have crates of glass micro spheres here from my home theater business so I can try using them with the resin too.
Aluminium has a high oxide content (especially if it is anodised) and surface oxide forms almost as soon as you have finished sanding it, so you need to be sure to give it a really good key, and bond it virtually straight away after cleaning with acetone. Realistically unless you are chemically preparing it, you will always have reduced lap shear strength due to the oxide layer, it just depends on whether the load experienced is actually enough to make that an issue. In most cases the bond is still strong enough.
In the case that it isn’t, chemical etching using some form of strong acid like sulfuric will sort it out. A simpler, less effective, solution is citric acid. Citric acid will also etch aluminium to a degree, but obviously not as well as a stronger acid.
Sorry, that wasn’t what I meant by that comment. They certainly aren’t the same thing by any means.
What I meant is that a toughened adhesive is a modified epoxy designed to have certain properties, one of which being a viscosity suitable for maintaining ideal bond gaps. If you have a base epoxy resin that has all the properties you need but isn’t viscous enough, then you can certainly just modify it with fillers to make it more suitable. Even if you need to give it more strength, there are fillers available that will do that too.
But no, an epoxy laminating resin with some filler powders in it is not the same thing as a manufactured toughened adhesive.
If you take a look at the data sheet, you will see that the results are given for Aluminium, and include the popular preparation methods.
The Araldite and the Loctite are comparable system, with very good bond characteristics to both composite and alloy.
If these do not work, then you could try a methacrylate adhesive such as Plexus.
They have a primer specifically for anodised alloy and it is very tenacious.
If your preparation is meticulous when bonding to composite, you will disbond the first ply it is attached to, before you separate the alloy off the surface.
I usually do post cure but I have pretty much given up on bonding flat cf parts to a flat aluminum surface until this thread. The results I was seeing were not just a low strength bond. It was more like no bond at all. I could easily peel the CF off the aluminum as if it was silicone if there was no mechanical lock.
I have had much better results adding aluminum inserts to cf tubes by wrapping the inserts in cf yarn or some other mechanical lock.
I have a little more hope now that a flat to flat bond is possible.
