Why couldn't foamy resin/epoxy w/fiberglass increase strenght to weight?

Discussion in 'Materials' started by Squidly-Diddly, Jan 12, 2012.

  1. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Lets say you had 3mm layup, but instead whipped the epoxy full of air(or other suitable gas) to fluff it out to 6mm.

    I'm thinking of something like whipped cream with tiny bubbles.

    Wouldn't that be more or less like other foam cores?

    Maybe have the two outside layers be non-fluffy normal, then fluffy in the middle.

    Couldn't that be like a foam core for strength, insulation and buoyancy, but with much of the benefit of fiber-re-enforced resin, as opposed to relatively weak foam like Airex?

    Plus, I'm thinking modulating the amount of gas entrained in the foam would allow all sorts of easy optimizations for different parts of the boat, instead of being stuck with one type of foam and thickness.


    PS-What is that engineering word I'm looking for that makes a structure with 'thickness' stronger than a thinner one, just because it creates more stress when you try to fold or bend it? "truss"?
     
  2. CatBuilder

    CatBuilder Previous Member

    Yes, that would certainly work. Doing it practically and reliably, on the other hand... I'm not so sure it would be easy.

    The foam we all buy (Airex, Corecell, Divinycell, etc...) are all simply that. They are just plastics (like epoxy) foamed up with some agent to create lots and lots of bubbles. You could certainly make the same thing with epoxy, but it may or may not have the characteristics you want at the end (including price and/or ability to resist cracking). I don't know... you'd have to test the resulting material.

    Essentially, when you mix in microballoons, you are doing the same thing, using the phenolic balloons to make little pockets in the epoxy like the air pockets you are envisioning.

    I think the term you are looking for is truss or most often said in the literature : Infinite I beam.
     
  3. ondarvr
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    ondarvr Senior Member

    There are products like this in the polyester world. They work for some situations, but not typically in load bearing structural applications. They are typically used as print blockers and panel stiffeners.
     
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  4. PAR
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    PAR Yacht Designer/Builder

    Epoxy loses a substantial amount of strength when whipped up. In fact, when doing physical properties tests, I found just adding fillers can lower epoxy strength in some columns of comparison, if mixed aggressively in the cup! Since learning this, I've used a whole new mixing procedure, that eliminates much of the bubble making. It's a slower, more deliberate technique, but does make a noticeable difference.

    Now, back to Squidly's idea, I think it has some potential, but at several substantial costs. I'll bet the cost of an epoxy foam will be quite high, compared to some of the lower cost structural foams. I'll also bet it'll be a fair bit heavier too. This coupled with the physical properties questions and the ability to make panels or voids, filled with this goo, uniform in density (bubbles like to float to the surface) will all combine to drive you nuts.

    I can picture a machine to make epoxy/foam panels, but this may be beyond the scope of what you're trying to do. Do some simple tests and compare them to the base lines offered over at West and see where you come out. Uniform density will be the one I'd be most interesting in seeing.
     
  5. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I'm thinking with micro-bubbles, like a paste, it takes longer for the bubbles

    to join up and rise or otherwise cause problems and the resin would set up before that.

    Maybe I'll ruin a few sets of egg-beater attachments trying this out.
     
  6. ondarvr
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    ondarvr Senior Member

    The polyester versions use a blowing agent that foams during application and are applied with spray equipment
     
  7. tunnels

    tunnels Previous Member

    You are way behind the 8 ball mate. you can buy foaming resins !! Its usually sprayed to get a even thickness . we used it through a chopper gun and ran the chopper slow so the foam was glass reinforced . Just use core matt same thing !! except they use q cells in a matt ! :confused:
     
  8. irineos
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    irineos land architect

  9. Herman
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    Herman Senior Member

    And in epoxy the same stuff is available as well. In marine application paddle blades come to my mind.

    Sicomin has 170 to 600 kg/m3 versions, in regular, cold curing, flame retardant, etc versions.
     
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  10. Roly
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    Roly Senior Member

    ATL have it here. Pricey tho'. I was thinking of using it to fill the voids
    around the steel stem structure above the bulb in my keel. Treat the steel with coal tar epoxy then bury in foaming epoxy and glass over.
    Suits me as you don't have to contain it to make it dense. Density is controlled by reactants.
     
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