Epoxy infusion in 2 step

Discussion in 'Fiberglass and Composite Boat Building' started by S17665, Jun 11, 2020.

  1. S17665
    Joined: Nov 2006
    Posts: 53
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: Europe

    S17665 Designer

    Hi Guys , i have to build a 10 m boat (fibercarbon sandwich ) using infusion method. I would like to know if is possible to perform in 2 step . First stack and then core + internal stack.
    I know well that the chemical joints in epoxy is basic then mechanical but what do you think about?
    Guaranteed delamination ?
     
  2. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    You need to explain the purpose and clearly define each stack.

    Stack A
    Stack B

    otherwise, it will be misinderstood

    you do not want to laminate glass without core as that bond is most critical

    If you

    Stack A -glass, core
    Stack B glass, core

    or
    Stack A -core, glass
    Stack B -core with glass, glass

    both would work.

    But not

    Stack A-glass
    Stack B-core and glass
    (This will result in air entrapment I'd say)

    be a little clearer about the reasons and the actual stack plans as there are others here wiser than me, but they will also want to know why and how in detail

    If this is just to watch the infusion to verify it is working; you can do it, but you lose table side finish. And you would need to buy the right core as a perforated core would be trouble filling and not bleeding out. Then you'd want to flip it and do the other side within the bonding window or you'd need to cleanup the panels some. And there would be other issues with panel reliefs for tapes to think through. Flipping would require supporting reliefs.

    just be a little clearer here
     
  3. Chris Rogers
    Joined: Apr 2020
    Posts: 20
    Likes: 6, Points: 3
    Location: Boston, MA

    Chris Rogers Junior Member

    In theory you can infuse any combination of skins and core and if the details are right it will be ok. I agree that core and top skin in one infusion would be the trickiest and I can't see a good reason to do this.

    Many people have infused just a skin on the mold and then wet-bagged core with filled resin (lighter and more control) and then detailed the core and come back to infuse the other (inner, outer depending on the tooling) skin. Biggest obstacle may be keeping the initial skin from pre-releasing from the mold while you do the core step. In terms of bond strength, with skin to core, primary bonds are not really an issue and with good prep it should be as good (or better) than doing it all at once.

    If you are using sliced / perforated core and detail the whole thing it may work fine to just infuse in one shot. This is done all the time. If you have complicated core fitting then maybe it would be neater (and probably lighter) to do in multiple steps - but also more work!
     
  4. S17665
    Joined: Nov 2006
    Posts: 53
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: Europe

    S17665 Designer

    Thanks for reply , i made several times the multistep infusion with vynilester but never with epoxy that is very choosy for the joint for example with vynil gelcoat so i am worried that the joint is only mechanical and not chemical . I have a complicated core as you say to improve shear stress then the shipyard is worried about the resin flow , stagnation and resin pot life doing it all at once. We know well that multistep change the mechanical proprieties of the lamination stack and anyway the boat is a high performance full carbon.
     

  5. Chris Rogers
    Joined: Apr 2020
    Posts: 20
    Likes: 6, Points: 3
    Location: Boston, MA

    Chris Rogers Junior Member

    Generally with the boats I have seen and worked on (both carbon and glass) that are laminated with epoxy (wet, infused or pre-preg) the inside skin (with a female mold) is very often secondary-bonded to the cured core and outer skin. The only time this isn't the case is with one-shot infusion. The structure is also almost always secondary-bonded too. This doesn't seem to be a problem because epoxy makes a tougher and stronger secondary bond than vinyl-ester with good surface prep.

    If the shipyard is worried then maybe there is something I am not understanding or aware of... there are plenty of resins capable of the open time you need to infuse a 10m hull especially if you use a staged infusion and mix the resin in batches.
     
    fallguy likes this.
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