Ganja Reinforced Panel impact test

Discussion in 'Materials' started by sigurd, Feb 11, 2009.

  1. sigurd
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    sigurd Pompuous Pangolin

  2. robherc
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    robherc Designer/Hobbyist

    I'm not a PROFESSIONAL engineer, but I think I got the general premise of the article:

    1. Hemp fiber is lighter than e-glass (doh, did they REALLY need a test to prove that?)
    2. Hemp-reinforced panels are stronger than polyester-only panels (doh again)
    3. At similar "fiber volume fractions" e-glass reinforced polyester (in this test, at 21% fiber volume fraction) had VERY slightly stronger than hemp-fiber reinforced polyester panels.
    4. Under the same conditions mentioned earlier, hemp-fiber reinforced panels received damage earlier than e-glass reinforced panels.

    ...I'd like to see the results re-calculated based on fiber WEIGHT, instead of just volume content...I think in that comparison, the hemp fiber would win out by a margin.
    ...also, I believe, the hemp fiber would likely win out very well on a graph of energy absorbed per COST!


    ...thanks for linking that article to us! :) *starts searching for ganja for "panel reinforcement"....* :p
     
  3. marshmat
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    marshmat Senior Member

    The British Navy ran on hemp for many decades, back when sailing ships ruled the seas. It's really quite an amazing fibre.

    A fibre/resin ratio of 21% is nothing to brag about, to be fair. But it is representative of what you would get in a cheap CSM layup. It looks like they found the hemp-reinforced polyester to be somewhat weaker than e-glass in most respects, and comparable in impact resistance. I'd be interested in seeing some more detailed tests with different combinations of hemp fibres, different layup techniques, etc.
     
  4. sigurd
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    sigurd Pompuous Pangolin

    A question about that. Is volume or weight ratio the normal thing to refer to when comparing resin/fiber ratio?
    Volume ratio would be rather difficult to ascertain?
    I have never seen anything to support that you can get higher resin/fiber ratio with some fibers than others.

    Back to topic: puff puff...
     
  5. robherc
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    robherc Designer/Hobbyist

    normally, from everything I've seen, you would go by WEIGHT for the ratio; my guess is they went by volume here because that was what they thought would be the most "fair" comparison between the hemp & glass fibers.
    As far as getting higher resin/fiber ratio with different fibers, if you go by VOLUME, I don't think you'll find too much difference, though glass rovings may be able to lay flatter (since they're smoother), and thus hold slightly less resin than "natural" fibers. Primarily, the type of fabric & the process used has the most effect on fiber to resin ratio (generalities):
    Hand lay-up with no vacuum process = high resin/low fiber
    Hand lay-up + vacuum bagging = lower resin/higher fiber
    Vacuum Infusion Process = lowest resin/highest fiber

    Random-oriented fiber mats = high resin/low fiber
    Woven fabrics = Lower resin/higher fiber
    Uniderectional fabrics/roving wrapping = lowest resin/highest fiber.


    ....It's 4:20 somewhere sig....pass that
     
  6. sigurd
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    sigurd Pompuous Pangolin

    As far as hemp goes, I find a high resin/fiber is often the strongest. I think the preferrence should be influenced by whether one is in the design phase or in the construction phase or just phasing out. Yeah, time to bunk.
     
  7. robherc
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    robherc Designer/Hobbyist

    Have you tested hemp composite panels, or are you speculating? If you've tested them yourself, PLEASE let us in on the info! :D (it'll save me a good deal of experimenting)
     
  8. sigurd
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    sigurd Pompuous Pangolin

  9. robherc
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    robherc Designer/Hobbyist

    Looks like they were doing some SERIOUS torture testing there, reading the article.

    The first vertical column represents the largest diameter or the area of delamination for a composite panel after it was compressed (imagine your ship being held in a giant clamp) & then struck with a hard object.
    The second column is the same measurement, but the panel isn't stressed prior to impact.
    The far-right column is for when the entire panel is under tension when impacted.

    The only really significant thing I see here is that the CF reinforcement seemed to have by far the lowest compression strength after the striker impact, thus it got crushed easier....guess I'll have to be sure never to get my carbon-fiber boat stuck in a giant "C"-clamp & shot at!
     
  10. Herman
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    Herman Senior Member

    My company has been involved in selecting natural fibers for composite construction, and both hemp and flax look very promising. However, this industry is still not fully developed, although some car manufacturers have parts produced in polyester and hemp or flax. Flax was somewhat easier to work with, but the fibers had to be worked in such a way that they were very itchy.

    One anecdote: The Trabant (eastern german car) was made from hemp and polyester, and when the moulds went to Egypt, they had to revert to glass again, as the goats were eating the cars...
     
  11. sigurd
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    sigurd Pompuous Pangolin

    Funny!!!

    damn druggies everywhere!
     
  12. eponodyne
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    eponodyne Senior Member

    I was about to start spouting off about how hemp would be a fantastic materials for rovings; then I remembered that we also call that sort of thing "rope."

    I also wonder how well a bamboo fabric would work. Maybe a hemp/bamboo blend? I bet it would be pretty expensive, at first. I also believe it would work a treat and be very sustainable, high-density agriculture.
     
  13. Herman
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    Herman Senior Member

    And about hemp: the great thing is that it is stronger when wet, so long live osmosis!

    Hmmm, I do seem like an expert now. OK, it is true. Dutchies are hemp experts... :)
     
  14. sigurd
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    sigurd Pompuous Pangolin

    I was trying to source heat treated bamboo locally, called "pro bambus" before I gave up and ordered ipe, makore and kingwood from the USA.
    It is very hard so I thought it would be a good skin material.
    I thought about it afterwards that maybe I am contributing to the death of the rain forests. :(

    Edit: There is also something called "steamwood", which is heat treated european wood, said to become much harder by the treatment, making exotic wood unnecessary. I wonder if steaming the exotic veneers will make them harder too? Ipe is already janka 3000!
     

  15. robherc
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    robherc Designer/Hobbyist

    Well, the best prices I've seen so far are:
    Hemp Fabric: $24(USD)/yd
    Bamboo Fabric: $15(USD/yd (Equivalent weight to 4oz e-glass)

    So yes, it IS expensive, and no, nobody seems to be making and natural version on "woven roving"...it'd take 5 or more layers of the bamboo fabric to equate to 1 layer of E-glass 18oz WR...and at over 30 times the price! I don't know about anyone else, but while I AM concerned about the planet, and being "eco-friendly," this cheap-skate is steering WAY clear of spending 30+ times as much as I have to for ANYTHING!!!
     
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