Awl -- Previously (on RW), I asked about coatings, waterproofing plywood.Now, in an interior environment (moisture not an issue), I'm curious about laminating an approx. 4' x 6' area of plywood with some other thin-ish, or even not so thin-ish material -- from formica laminates, to .030 SS or Alum sheet, to 1/4" rubberized tile, linoleum.I recall carpenters using gobs of white elmers glue for large-contact wood areas, in building mezzanines in lofts, etc.Then there is elmer's carpenter's/wood glue, mastics for tile (what's a mastic, inyway??), epoxies, a zillion other adhesives.The general Q is: when to use what for what?For example, in the .030 SS/Alum I will place over 1/2" ply, I would like to be able to just roll on some suitable adhesive over the full 4x6 area, and press them together, proly via weight plates.What would good choices be? How thick?Interestingly, an increase in thickness from ..5 to .532 will generate about a 13% increase in stiffness, since stiffness is proportional to the square of thickness, but ONLY if there is no slippage between the two layers. Thus, the requirement for full-surface bonding, via adhesive.Ackshooly, that 13% inc in stiffness presumes similar materials. I measured that 1/4" alum plate is as stiff or stiffer than decent 1/2" ply, so the increase in stiffness is likely to be a bit more than 13%.Inyway, I'd like an idea of how to gauge the type of adhesive to application. Bang fer the buck is always good, as well.Along these lines, I see all kinds of two-part epoxies, specialized for wood, metal, ceramics/glass, etc.Afaict, they all work the same on everything, with perhaps the exception of things like nylon, delrin, other "greasy" plastics. Any opinions on this?

Proportional to the *cube* of thickness.Correct.Laminating materials with different Young's modulus is not generally additive.If you're laminating on the neutral axis, the situation is not demanding. White glue works fine for two layers of softwood, of equal thickness. Shear loads are low.When the lamination occurs off the neutral axis you have bigger shear loads on the glue line, and they can be quite high.Aluminum is a bugger to bond to if you need high strength. Commercially, they use PAA -- phosphoric acid anodizing -- and you actually bond to the anodizing, not the aluminum. I've described the "scratch-in" method of getting a good bond to epoxy several times here. That would work, but it's not practical for a big surface. It's good for small things.When I have a question like that I get on the phone with 3M, Loctite, or one of the other big guys, and keep bugging them until I get to an engineer who knows what he's talking about. Ask about self-etching adhesives and adhesive...

Theory of Adhesives?

Jul 12, 2011 41 Replies

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Robatoy 15 years ago

Laminating aluminum, clear, brushed, shiny comes in many diffent sheens, and is already prepped for laminating. Just about anybody sells that stuff, Wilsonart, Formica, Arborite, Nevamar.

Yea.... what DOES he want? LOL

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Tim Wescott 15 years ago

But is it load bearing? Can you laminate it onto plywood, then actually use the strength of the aluminum?

Or is it just a way to make it shiny?

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