1st Carbon laminate testing

Discussion in 'Boatbuilding' started by BWD, Jun 4, 2007.

  1. BWD
    Joined: Aug 2006
    Posts: 229
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    Location: Virginia, US

    BWD Senior Member

    I am building a 18ft sailing canoe/proa detailed elsewhere in these forums, and have gotten to the stage of reinforcing the gunwales.
    The hull is 1/4" WRC, wrapped in 9oz s2 glass/epoxy.
    The inwales are WRC, 3/4" thick by variable height.
    To avoid too many thwarts or a wiggly boat I decided to use uni carbon and glass to reinforce the light inwales.
    The layup at inwales is:
    6 oz Eglass
    6.7 oz 12k uni carbon
    6 oz Eglass

    I built a 1 foot section of this laminate to test its strength and my application technique.
    To test it I supported it at each end and parked my truck on top of it.
    Load ~850#
    Deflection ~1/8"
    Very satisfactory.
    However, examining the laminate I can now see that there is slight checking or apparent delamination at every "proprietary heatset" fill thread.
    The carbon in question is hexcel GA060.
    Never worked with it before.
    My questions:
    Do you always get this with this material?
    Is it because the fill thread does not really wet out?
    Is it likely because I only put one layer of Eglass over the Carbon?

    I hope to avoid loads of this size on the gunwales, as sailing weight will be under 500#, but I would like to know what is going on with this laminate anyway....

    Any advice appreciated!
  2. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Hexcel's data sheet on this material http://www.hexcel.com/NR/rdonlyres/DF70FC51-3A32-4158-9565-0083AFA6B340/0/GA060.pdf yields little insight on the problem. It has a fairly high fill thread density for a uni, though.
    Hexcel does specify that GA060 is for "recreational low pressure composites", whatever that means. My guess is that the heatset fill threads, being thermally fused, don't allow much if any resin to penetrate. Other than being extra careful to get a thorough wet-out, I doubt there's much you can do about it. It shouldn't compromise the strength very much, I would think.
  3. BWD
    Joined: Aug 2006
    Posts: 229
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    Location: Virginia, US

    BWD Senior Member

    Thanks Marshmat.
    The fill looks like monofilament, I guess it just doesn't really key to the resin.
    I think "recreational" means it is PAN based, but the lowest grade.
    Still pretty good if it allows me to park my truck on top of a pared down furring strip.:)
    More info:
    Tested at ~850# load (tire of my vehicle), wood cleats of varying size between tire and sample yielding:
    1) 13.5 in^2 =>63psi, ~2-3mm deflection
    2) 9.75in^2 =>87psi, ~3mm deflection
    3) 5.25in^2 =>162 psi, maybe a wee bit more deflection...
    Small numbers, but my "test rig" is not equipped to do more....
    Here's how it looks now, for the record:

    Attached Files:

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