Infusing flax

Discussion in 'Fiberglass and Composite Boat Building' started by rob denney, Jun 19, 2020.

  1. rob denney
    Joined: Feb 2005
    Posts: 756
    Likes: 111, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    I was given a couple of rolls of flax cloth. before using it in the boat, I infused a couple of stacks of flax and fibreglass. Same weight of cloth, but the flax was a little thicker. The infusion filled both stacks at the same time. After half an hour, the flax side was about 2 degrees C warmer (21C vs 19C), which climbed to 22/24C by the end of the infusion when I put a heat blanket over the job to cure it.
     

    Attached Files:

  2. gonzo
    Joined: Aug 2002
    Posts: 14,507
    Likes: 659, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Are you building a boat with a mix of flax and fiberglass reinforcement?
     
  3. rob denney
    Joined: Feb 2005
    Posts: 756
    Likes: 111, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    Maybe, but probably not in the same laminate stack. Tests are on going. Is there something I should know if we do?
    0
     
  4. ondarvr
    Joined: Dec 2005
    Posts: 2,330
    Likes: 259, Points: 83, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    What is it you're trying to achieve by using a fiber that's not typically used in production?
     
  5. rob denney
    Joined: Feb 2005
    Posts: 756
    Likes: 111, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    Nothing in particular. I got given the flax, am running some tests (infusion speed, resin uptake, toughness, stiffness) to compare it with f'glass. I noted the temperature anomaly, thought I would see if anyone knew any reasons why. Apart from the zero cost, there is the 'green' benefit which is important to potential backers of the boat which is a zero emissions 24m/80' Harryproa for servicing remote Pacific villages.

    My next post would have been asking what these benefits actually are as I am unsure of the environmental benefits of melted sand (fibreglass) vs grown fibres (flax). If anyone has any information, I'd like to hear it.
     
  6. ondarvr
    Joined: Dec 2005
    Posts: 2,330
    Likes: 259, Points: 83, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    These alternative fiber awareness tangents pop up when someone wants to promote a fiber for a specific reason, which is typically their own profit.

    You can use just about any fiber to make an item and it will work, at least fairly well.

    I've been involved with some customers that were promoting hemp fibers for composites. It worked, not nearly as well as glass, but could be used. There were grants and money to promote these projects, these builders were just following the money. Once the money dried up every one of the accounts stopped using it and reverted to glass.

    You can do like many in this situation do. Make it from glass and add just enough of the "fiber of the day" to qualify for funding and/or promotional concerns.
     
    Last edited: Jun 21, 2020
  7. gonzo
    Joined: Aug 2002
    Posts: 14,507
    Likes: 659, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    There is no "green" advantage. Fiberglass is inert silica, basically beach sand. Flax was used in the early days of reinforced plastics and given up because it is more expensive and weaker than fiberglass. Also, it is less "green" because it is using land that could be growing food.
     
  8. Eric ruttan
    Joined: Jul 2018
    Posts: 153
    Likes: 17, Points: 18
    Location: usa

    Eric ruttan Senior Member

    The renaissance of flax fibers - Materials Today https://www.materialstoday.com/composite-processing/features/the-renaissance-of-flax-fibers/
    way greener, in that less carbon to make and is a carbon sink. also not a food displacing crop. so it seems.

    for the reader Thixotropy - Wikipedia https://en.wikipedia.org/wiki/Thixotropy
    I wonder if the finer glass fibers force the resin to stay thixotropic longer, leading to further penetration, while the larger flax fibers reduce thixotropic effects as the passages are bigger.

    It may be the same for the heat. thin epoxy against high density and high specific heat glass keeps cool and thixotropic. thicker epoxy against low density low specific heat flax has an inverse thixotropic effect, reducing penetration?
     
    Last edited: Jun 23, 2020
  9. gonzo
    Joined: Aug 2002
    Posts: 14,507
    Likes: 659, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    I suspect any claim that flax or any other crop is not a "food displacing crop" is a marketing ploy. I suppose I could change my opinion if they grew flax on bare rocks.
     
  10. Eric ruttan
    Joined: Jul 2018
    Posts: 153
    Likes: 17, Points: 18
    Location: usa

    Eric ruttan Senior Member

    I'll defer to your farming expertise.

    I was under the impression flax is an actual food crop that also produces fiber. But I know nothing.

    Flax - Wikipedia https://en.wikipedia.org/wiki/Flax
     
  11. gonzo
    Joined: Aug 2002
    Posts: 14,507
    Likes: 659, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    There are different varieties. When it is cultivated for food (linseed oil and seeds) it grows as a bush. The variety for fibers grow to about 4 feet tall and is harvested before the fruit matures, which degrades the fibers. Kind of like pot.
     
  12. ondarvr
    Joined: Dec 2005
    Posts: 2,330
    Likes: 259, Points: 83, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    Infusion resins, both epoxy and polyester don't typically have a thixitrope (silica) added, there's no need for it, it will inhibit the actual infusion process.

    Hand laminating resins do have thixitropes, but they don't work nearly as well in epoxy.
     
  13. DCockey
    Joined: Oct 2009
    Posts: 4,703
    Likes: 315, Points: 83, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    Resin curing is exothermic which tends to raise the temperature of the laminate. Could the temperature difference be due to difference in the specific heat of flax fiber versus glass fiber?
     
  14. gonzo
    Joined: Aug 2002
    Posts: 14,507
    Likes: 659, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Glass will have a higher thermal transmittance than flax, which would make sense it doesn't heat up as much.
     

  15. rxcomposite
    Joined: Jan 2005
    Posts: 2,100
    Likes: 226, Points: 63, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    Rob- Here is the material property of the flax and other fibers. If you look at the comparison you will notice that flax strength is lower than glass. That means if you want a better composite laminate, the outside layer should be glass and the inner layer flax. Much like putting CSM sandwiched by WR.

    I could not find the shear properties of flax. If I can find it, I will be able to determine how thick the proportions will be.
     

    Attached Files:

Loading...
Similar Threads
  1. ahender
    Replies:
    4
    Views:
    312
  2. CristianJ
    Replies:
    4
    Views:
    846
  3. Dejay
    Replies:
    44
    Views:
    4,247
  4. Zac Penn
    Replies:
    20
    Views:
    4,025
  5. Tungsten
    Replies:
    30
    Views:
    3,496
  6. svquintana
    Replies:
    20
    Views:
    8,035
  7. Jetboy
    Replies:
    17
    Views:
    2,639
  8. nicste
    Replies:
    4
    Views:
    1,387
  9. Steve W
    Replies:
    201
    Views:
    20,919
  10. dshowalt
    Replies:
    5
    Views:
    1,716
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.