Layer on layer vs. solid
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    Default Layer on layer vs. solid

    Hello. If I have two plates, one is made of multiple layers of sheet metal fixed together with jb weld and the other of the same metal but solid, what will be the difference in strength? The same question regards a sheet wrapped tube vs a solid.

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    Quote Originally Posted by Develop View Post
    Hello. If I have two plates, one is made of multiple layers of sheet metal fixed together with jb weld and the other of the same metal but solid, what will be the difference in strength? The same question regards a sheet wrapped tube vs a solid.
    The shear strength of the bond.

    Shear travels in a 45 degree angle thru the center of a beam, so figure on that if your material composite is in bending.

    In other news:
    Using wire or flat strip in layers instead of solid (allows very hi prestressing)
    https://www.nationalboard.org/SiteDo...n_Fridlund.pdf
    Last edited by digger doug; 02-14-2020 at 02:10 PM.

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    A chain is only as strong as it's weakest link. In your example it would be the JB Weld.
    But I guess we would need to know your application. What is the intended use?

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    Quote Originally Posted by Develop View Post
    Hello. If I have two plates, one is made of multiple layers of sheet metal fixed together with jb weld and the other of the same metal but solid, what will be the difference in strength? The same question regards a sheet wrapped tube vs a solid.
    What do you mean by "strength"? What is the proposed application? It matters a lot.

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    I would guess it would depend on which way are you trying to bend this thing.

    Are you putting JB Weld between the leafs of a leaf spring, and trying to make
    it stronger?

    Or are you trying to bend the leaf spring sideways?

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    Laminations, common in electric motors, are always weaker than a solid piece of the same or equivalent material.

    Whether you need the strength is a different story.

    Also, there are much better adhesives available, purpose made, for laminating metals.

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    Laminations in motors are not bonded together. I'm sure there are volumes written on laminar strength.

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    "Which is stronger?" From an engineering point of view, the first thing that comes to mind is that is a very vague question. There are many qualifying factors that are not mentioned.

    First, there are several ways that a part can be stressed: compression, tension, torsion, and, of course, various combinations of those three. And then, each of the above basic modes can be applied in each of three directions. As for the combinations, I am not even sure how many there may be. But you have at least ten and probably fifteen, twenty, or perhaps even more different combinations.

    Then, there is how those stresses are applied. Many possibilities exist: a single hole with a hook or stud in it, clamped all along an edge, some sort of surface attachment, center of the side, corners, etc.

    Almost all of the above and many more possibilities will yield a different number. For instance, if you are applying a compressive force that is normal (perpendicular) to those lamination layers, then the compressive strength of the metal will be almost completely unchanged but the epoxy, which would be in a thin layer, would probably compress more. Overall you may need a very sensitive measurement to detect any difference. On the other hand, if you reverse that stress and it becomes a tension in that same, normal direction, then the solid would probably be clearly stronger as the epoxy would become the weak link. I don't know, but it may be possible that some of those modes of stress may be better resisted by the laminated assembly.

    Another example may be laminated cannon barrels. They can be stronger and last longer than barrels cast in one piece. But if you test those same barrels with a compressive force on their sides ON THE OUTSIDE, instead of with the explosive force on the inside, then the solid barrel would probably win.

    Different arguments would apply for almost each of the other basic modes of stress and for the combinations. A stress analysis needs to be done with specific geometry and dimensions, not just a vague laminated vs. solid comparison.

    Yea, I know, it's proprietary and you don't want to talk about the details. Build one each way and test them to the point of failure. Then you will know. Actually, if it's important, you really should test several of each. How many would depend, at least partially, on how much the results vary.

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