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Thread: Laminating KEVLAR

  1. #1
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    Default Laminating KEVLAR

    Hello



    Does anyone have experience of laminating KEVLAR cloth? (500gm/m^2)



    If so I would appreciate any guidance or tips...



    Ian

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    Default Re: Laminating KEVLAR

    Hello Ian,

    Using Kevlar is good for bottom hull, or anytime you need something light, and strong against shocks or scratches. The trouble with it is it refuses to follow curves easily, tends to act like a spring. I used it for surfboards , with epoxy resin. It would be easier to use it with polyester resin, due to quicker hardening. If you need to follow an angle like front hull, you may wrap the kevlar + resin with an alimentary film, as to maintain it glued to hull. The film doesn' t glue to resin , if it' s flat enough, you can remove it easily when resin is dried. The best use of kevlar is to reinforce flat parts of hull, or angles , where hull scratches ground.

    It should need a very long time and a lot of skill to make a full kevlar hull. And it should be too souple, that' s why we use carbon mixed with kevlar as stiffener, for boards and canoes.

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    Default Re: Laminating KEVLAR

    When I worked with kevlar, I purchased the slow curing (tropical) hardener (2-3 days cure time). I would layup the layer of kevlar first, then apply a layer of glass cloth on top of it while it was still wet. The glass cloth does 3 things:

    1. adds strength

    2. holds the kevlar in place on all but the most drastic curves

    3. Allows sanding when cured. Sanding a kevlar laminate alone will result in alot of fuzz because you end up sanding the matrix and not the cloth!

    I'm not yet convinced that it is worth the trouble.

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    Default Re: Laminating KEVLAR

    Hi



    The kevlar is to be used for the propeller containment - I want something lighter than the 'regulation' 6 layers of 450 gm (13oz) CSM, which would come in around 16kg (35lb). It will be a single curvature wrapped around a 1.5m (59") propeller, on a simple former. This particular material is used for blade containment on aero gas turbines.



    I plan on doing some experiments to determine the construction which is 'equivelent' to 6 layers 450gm csm, probably either:



    1 layer 6oz cloth, 1 layer kevlar, 1 layer cloth

    or

    1 layer cloth, 1 kevlar, 1 CSM, 1 kevlar, 1 cloth

    or

    upwards of this.



    Ian

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    Default Re: Laminating KEVLAR

    You can lay up kevlar easily. Just treat it as another layer of glass. Make sure you sandwich it with a layer of csm on the inside and the outside, and use pigment in the resin. Kevlar will degrade in UV light (sunlight) if it is not covered. Also kevlar is quite thirsty on the resin.



    jamie

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    Default Re: Laminating KEVLAR

    I forgot,

    I conform: do not try to sand if kevlar is used as outer layer, plushes ! And plushes become sponges.

    If you use it as a duct close to propeller path, aerodynamic trick is : don' t sand it at all, let it a little bit rough, it' s better ( too long to explain here, but believe me ).

    I think using a slow hardener is not so good. Hardening must been achieved in a precise time to insure strength quality, for any deviation in this time, you lower Kevlar quality.

    In my opinion, I should use several kevlar layers on the inside to prevent gravels holes in the duct, and fiberglass layers on the outside for strength and better look, and colour.

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    Default Re: Laminating KEVLAR

    DON'T use polyester resin to lay up kevlar, it does not bond well enough to kevlar to properly transmit load to the fibers.

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    Default Re: Laminating KEVLAR

    Yes and no,

    Kevlar is best used with epoxy resin, BUT:

    if your hull is in fiberglass + polyester resin, and you want to reinforce part of hull with kevlar material, you MUST use polyester resin, otherwise, the added layer has many chances ( or risks ) to stay on the first obstacle you' ll bump in. It will flake off at the first sun ray or schock.

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