Handwoven Kevlar

Discussion in 'Materials' started by Stormydog, Oct 9, 2017.

  1. Stormydog
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    Stormydog New Member

    Will a herringbone or point twill with a plain weave layer next be structurally strong enough or should I add another layer of fiberglass?
     
  2. upchurchmr
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    upchurchmr Senior Member

    Are you making bullet proof vests?
    An airplane? Subsonic or supersonic?
    A submarine - how deep?

    What are you talking about?
     
  3. PAR
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    Ditto the previous comments. You'll need to qualify the question a bit to get any reasonable reply. Hand woven high tech fabrics aren't such a good idea, if strength and typical physical attributes are to be insured. I can understand a small project might warrant hand work, but given the availability of these fabrics, the modest cost for a small project doesn't seem unreasonable. On a larger project, well you'll make a career out of hand working these materials. Lastly, why are you employing 'glass fabrics in a Kevlar laminate? The two have quite disimular physical properties, meaning the 'glass will yield long before the Kevlar, making is a wasted/weakening layer in the laminate stack. As a rule, these types of fabrics need some engineering to take advantage of their attributes, or you're just wasting resin.
     
  4. TANSL
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    TANSL Senior Member

    That is totally true so it will be important to decide on which layer each material is placed. The correct thing is that the more resistant material, Kevlar, is placed on the outer layers of the stack.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Typically the Kevlar is placed the furthest away from the areas of impact, which is usually as the innermost layer, unless you use a concealment layer in the stack, such as mat of a finishing cloth. These add nothing to the laminate stack, though can make finishing and fairing much easier. Without a much better idea of what the OP is doing, much more than generic replies will be difficult.
     
  6. TANSL
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    TANSL Senior Member

    You may be right, but I am not talking about impacts but rather resistance to the design pressures of a stack of laminates.
     
  7. upchurchmr
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    upchurchmr Senior Member

    I bet he is going to make a ZOMBIE costume for Halloween.
    Too busy to respond.

    Why won't we help!!!!!

    Kevlar is needed due to all the Zombie hunters out there.

    Tansl - good to know what you were referring to. Perhaps you could say it to start with.

    The impact comment is completely true - but what if he's making something that needs no impact
    This whole thing is a waste, until the OP answers.

    Last time I looked at kevlar structure it was for manifolds to route air in commercial airliners - No impact, no actual structure - just the lightest possible tube. :D
     
  8. TANSL
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    TANSL Senior Member

    Yes, it is probable that I did not detect correctly what was being talked about and that is why I have expressed an opinion that was, perhaps, not appropriate.
    I am sure that these tubes will have to fulfill some more requirement that justify the use of this material because, I suppose, there are materials lighter than kevlar.
     
    Last edited: Oct 10, 2017
  9. Stormydog
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    Stormydog New Member

    Thanks for the response. I really don't have a need for a bulletproof vest, it's the flying monkeys I have to worry about if I get caught using fabric scissors on Kevlar fabric. I doubt if anything will help in the when the Zombies attack again. This is a small practice project, a motorcycle tour pack, to help with a larger kayak and use of vacuum pump. Reason for hand-weaving? Everyone has standard issue twill or plain weave. Kevlar is a bonded string and does not stick to itself like most natural fibers. It is not very elastic, but I am wondering how tight I must weave it to have the structure and still maintain flexibility.
     
  10. upchurchmr
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    upchurchmr Senior Member

    Tansl,

    Please let me know the next lightest material.
    I spend lots of years trying to find one.
    At the time Spectra was not available, and it didn't meet the 250F requirement I had.
    And you are wrong about the tube requirements, I talked to the designer.

    Alan, sorry for the distraction.

    Generally the weave does not effect the structure. Epoxy (etc) locks the flexible fibers into a shape. The flexibility you get depends upon the finished thickness for a woven product.
    You really can't trust any natural fiber to stick to itself for something like you are building. If you did you would have a fabric pack, which collapses.

    If you want to hand weave, just start with thicker strands. Or see if you can find a woven tape, then weave that. That would give you a much different look than typical laminates.

    Are you picking Kevlar for the color?
     
  11. Blueknarr
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    Blueknarr Junior Member


    Not very. I remember when Kevlar halyards were the rage, and not a few were broke because to small a diameter pulleys were used. Kevlar doesn't like to bend.
     
  12. Stormydog
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    Stormydog New Member

    I am using braided Kevlar string because it is easier to handle as a yarn. Carbon tow will probably give off too much dust when dragged through heddles or a reed requiring breathing and eye protection. Kevlar is bonded and easier to handle, but will float in the epoxy so a vacuum must be used. Will an unbalanced or 1/2 twill like blue jeans be flexible enough to follow a curve, but sturdy enough to hold shape after drying and subjected to pressure from air or water? Will it still crack the epoxy if two or three layers of differing weave patterns are used?
     
  13. upchurchmr
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    upchurchmr Senior Member

    I think you are just going to have to try it.
    We don't know what the tour pack shape is, but in my imagination, it will probably a lot more severe test of draping than anything on a kayak.
    You might get the closest thing you can find in glass and see if it will drape without darting.
    A 5 harness satin has a lot more drapeability than plain weave.

    Really, again, the weave has nothing to do with the finished flexibility (when bonded or infused with resin). The weave counts before the resin goes on.

    I build wood kayaks with plain weave glass on the outside and inside - neither laminate requires darting.
    Something that also matters is just how thick the laminate ends up being. 60z is easy on a kayak. 10oz is harder.
    How thick of a laminate are you wanting? Will the kayak have a core or will it be solid laminate?

    Well, I finally found what a heddle is. But I don't understand the weaving I have seen on the internet. I'll keep looking.

    The kayak I make requires cloth about 3+ feet wide. 24" wide boat. The plain weave on a simple kayak like mine gets twisted around in order to lay down. The pattern you imagine on the outside of the kayak may be distorted.
    You sure are setting up a real trial for yourself - good luck.
    Please post pictures of the weaving, tour pack, and the kayak.
     
  14. Stormydog
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    Stormydog New Member

    Epoxy resin vs polyester resin? Heat cure vs Vacuum cure? Research says that Chemically Epoxy binds better with Kevlar and heat cure is better than vacuum. Heat up the resin in a double boiler or hot water?
     

  15. SamSam
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    SamSam Senior Member

    Using vacuum is not part of the curing process. Heat cure means applying heat after layup or set up to accentuate the thermosetting properties of those resins.
    Heating the resin beforehand will cause problems.
     
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