Difference in laminate strength?

Discussion in 'Fiberglass and Composite Boat Building' started by Nojjan, Jun 26, 2008.

  1. Nojjan
    Joined: Sep 2006
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    Nojjan All thumbs...

    I wonder, is there a difference in the strength of the following two laminate sequences?

    Sequence 1
    1200g 0/90
    1200g +/-45
    1200g 0/90

    Sequence 2
    600g 0/90
    600g 0/90
    600g +/-45
    600g +/-45
    600g 0/90
    600g 0/90

    Best regards / Nojjan
     
  2. the1much
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    the1much hippie dreams

    i play with glass,,but dont have nothin t do with the mathematics,,,,but to me,,the second sequence would be resin rich,,,,which makes it hav less strength and more weight then the first.
     
  3. Nojjan
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    Nojjan All thumbs...

    ...resin rich huh, what if I vacuum bag also? any difference?

    /N
     
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  4. Knautcal
    Joined: Apr 2008
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    Location: Mississauga

    Knautcal Junior Member

    Hi
    You will have a better lamination schedule with the first sequence. It will give you higher stiffness with little gain in weight. It will also be effected as to the type of resin you use as not all resins are created equal.

    Cheers
     
  5. the1much
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    the1much hippie dreams

    dont know,,sorry,,,i dont do bags,,hehe,,but i still think it will work out the same,,it takes more resin to wet out 2 pieces of cloth,then 1 piece of equal weight.,,,but ask a bagger to be sure,,,i dont wanna give ya crappy info. ,,hehe ;)
     
  6. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    Nojjan,

    We sometimes substitute twin layers for a single, but I have never substituted the whole layup....is this a hypothetical question or a real scenario?

    The answer i expect will be a result of the extra resin as stated above, the less resin the stronger the laminate would be. We use vacuum baggin and resin infusion on our layups, but strictly follow NA schedules. Two half layers would not be as strong as a single double thickness layup ( I believe).
     
  7. Nojjan
    Joined: Sep 2006
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    Nojjan All thumbs...

    The question is theoretical but I think it has some merit (at least for my own education). I guess the conclusion so far is that I will end up with a higher resin-to-glass ratio (more resin) for the thin layers compared to the thick layers. Now, why is that, if the glass is of the structure shown in the attached picture?

    Sorry for my endless questions, I am just trying to learn. / Nojjan
     

    Attached Files:

  8. the1much
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    the1much hippie dreams

    wet a piece of paper towel,,,use just enough water to wet it,,,then add another layer,,,see how much water you have used,,now take a paper towel and fold in half (use as a 1 thick layer),,now wet that out,,,,,,see,,,MUCH less water was used.
     
  9. waikikin
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    waikikin Senior Member

    Nojjan, I couldn't tell you for sure, but where & how fabric overlaps are placed (dependant on a large size panel or whatever?) could well have some bearing on the neatness & overall "strength" , thickness/stiffness & also the quality of the fabric & shape of the fiber bundles in the fabric as to how it lays & packs down & also consder "mirror" inversion especially of the 0/90 in half of the stack. How about you make some & test pieces & bash em up so we all know. Regards from Jeff.
     
  10. Nojjan
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    Nojjan All thumbs...

    I think I will try that little experiment, even for guy like me (all thumbs..) I should be able to acomplish something reasonable for a test. Thanks for the input guys, I'll get back to this when I have some results (just got to find the correct fabric). / N
     
  11. TeddyDiver
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    TeddyDiver Gollywobbler

    Any info how much does it (resin richness) influence strength?
     
  12. the1much
    Joined: Jul 2007
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    the1much hippie dreams

    it as at to do with it,,,,,kick off just some resin,,,throw it on some concrete,,now try with some cured glass and resin (done correctly),,,,now do some glass in a pan,,and get ALOT of resin in there with it,,,now throw that,,,,it may not "break" into pieces,,but the resin will break off,,or crack,,,and once you have that crack,,,ya might as well call it goodbye ,, till its fixed right,,hehe ;)
     
  13. TeddyDiver
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    TeddyDiver Gollywobbler

    :D :D
    I was thinking something more "accurate" way to estimate. Like having 10% more (than ideal) resin gives X% less strength against vertical impacts, Y% less modulus..etc
     
  14. the1much
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    the1much hippie dreams

    hahahaahaha ,,,:D ,,,do it and let us know,,,hehe ;) ,,like i said before,,,sorry,,i can only count to ,,,1...2....3....jump,,,,hehe ;)
     

  15. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    And hell I won't.. I'll just add a bit more than Dave Gerr's Scantling Rules state and be happy with that...
    Saving the math for horse races :D
     
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