spectra vs kevlar?

Discussion in 'Materials' started by sigurd, Feb 18, 2009.

  1. apex1

    apex1 Guest

    Interesting. The test setup looks pretty loopy, tipically "scientific" madness. Different impact velocity, not related to specimen thickness (wich is different for what reason?), or another obvious value ? Imho the footnote says manipulated, nothing else. Maybe I´m just too stupid to understand?
    Worthless results.
     
  2. sigurd
    Joined: Jun 2004
    Posts: 827
    Likes: 8, Points: 18, Legacy Rep: 65
    Location: norway

    sigurd Pompuous Pangolin

    I'm not clear whether the impact velocity listed is the one where they considered the sample broken?
     
  3. sigurd
    Joined: Jun 2004
    Posts: 827
    Likes: 8, Points: 18, Legacy Rep: 65
    Location: norway

    sigurd Pompuous Pangolin

    Attached Files:

  4. apex1

    apex1 Guest

    Think so, but I´m not shure either. And why the hell different thickness, why "normalized" data? The specific energy to peak force could provide a good database, but "normalized" ? It is so easy (if you are not a scientist, teacher or lawyer), same size of samples, gives different velocity at impact before it brakes, proper result we could work with. nada...
    very interesting data (and very clear) for the surfboard test.

    Regards
    Richard
     
  5. apex1

    apex1 Guest

    program laminate

    Sigurd, if you understand some German, here is a download of the "LamiCens" Prog. Excel based and easy to understand. You can calculate every sort of fiber resin mix to very exact values! Must register and you have immediate access to the DL. Btw. their onlineshop (also in English) is really one of the best for the industry.

    http://www.r-g.de/laminatberechnung_registrierung.html
    and this is a REAL test:
    http://download.r-g.de/rg_dokumentation_whz.pdf
    unfortunately (for you) in German only, and no spectra.

    hope I could help a bit.

    Regards
    Richard
     
  6. dccd
    Joined: Mar 2007
    Posts: 21
    Likes: 2, Points: 0, Legacy Rep: 29
    Location: south US

    dccd Design director

    Hybrid

    The drive to use composites has always been to reduce weight in structures. That is probably why the testing is of different thicknesses, the samples are all of a common weight (see specific gravity). The example given of monolithic materials is less typical than the use of interwoven polymers (see image). Carbon has always been champion of stiffness, Kevlar and now Spectra better in tension. The science of the interaction among the fibers is probably less understood. However, think on the scale of the fabric where none of the threads are straight, they are like sine waves. if the yield (beginning to stretch) of carbon is less than its hybrid neighbor spectra, the carbon straightens out more. The Kevlar can yield and then add its better tension strength to the matrix. Hope that helps.
     

    Attached Files:

  7. sigurd
    Joined: Jun 2004
    Posts: 827
    Likes: 8, Points: 18, Legacy Rep: 65
    Location: norway

    sigurd Pompuous Pangolin

    Apex1, I'll check them out. don't understand german unfortunately.
    Edit: I'm unable to shift from sheet1 to the other sheets in the spreadsheet..?

    dccd, I don't see the correlation between specific gravity and the sample thickness in the "google book" test. I couldn't find the reference for how they made the samples.
    The weave thing you explained sounds reasonable.
    I don't know if the stuff witchcraft use is a dyneema/carbon mix or separate fabrics. For me it would be carbon uni (or rather tows) under spectra, if i can get it, I suspect these people only want to sell a 100yd roll and I only need 30yd. It is 4.1oz plain weave, 60" wide and 15.50 (us or canadian, not sure) per l.yd. if anybody is interested in chipping in.
    I assume none of you read the "witchcraft" description of kevlar/carbon fabric, since it is on the "customs" technical page.

    I had never heard about "h-glass" - it is also described.

    I am assuming creasing is similar to buckling?
     
  8. apex1

    apex1 Guest

    And YES creasing is buckling.
    Some results of a sample laminate. Attached

    Regards
    Richard
     

    Attached Files:

  9. hardshell
    Joined: Feb 2009
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: New England

    hardshell New Member

    The third ingredient that needs to be considered here is the binder. Vinyl, poly, or epoxy resin will all add slightly different characteristics to your composite. Think of baking -- you mix a few ingredients together and they taste like the mixture that they are. Add a binder and some heat and you can get cake, cookies, or bread with only slight variables in ingredients.
     
  10. apex1

    apex1 Guest

    Ähhh..sorry hardshell, did you read this thread?...........:rolleyes:
    But thank you anyway.

    Regard
    Richard
     
  11. sigurd
    Joined: Jun 2004
    Posts: 827
    Likes: 8, Points: 18, Legacy Rep: 65
    Location: norway

    sigurd Pompuous Pangolin

    Doesn't work, maybe because I use OpenOffice. Oh well.

    Apex1, you make it so I have to go back and reread all your posts... often adding a little bit of help and info afterwards... :)
     
  12. apex1

    apex1 Guest

    Sorry, I have a very poor Internet connection here in Turkey, uploads can take as much as 30 minutes for 100kb, (Europe?!). So I post the reply and edit immediately to make the upload in the background. I know edited post can be annoying, sorry.

    Regards
    Richard
     
  13. sigurd
    Joined: Jun 2004
    Posts: 827
    Likes: 8, Points: 18, Legacy Rep: 65
    Location: norway

    sigurd Pompuous Pangolin

    No, not annoying
     
  14. sigurd
    Joined: Jun 2004
    Posts: 827
    Likes: 8, Points: 18, Legacy Rep: 65
    Location: norway

    sigurd Pompuous Pangolin

    What I wonder also is whether spectra/dyneema and also aramids have to be coated or treated to bind with epoxy. advancedcompositetraders is the correct link for the spectra I mentioned. They said it is compatible with epoxy.
     

  15. apex1

    apex1 Guest

    Yes it is compatible, a test is shown on R&G website, but it is said also, that it is very difficult to cut and almost impossible to sand! The fibers and tissues that I found have no coating.

    http://www.dsm.com/en_US/html/hpf/products.htm

    http://www.swiss-composite.ch/pdf/t-dyneema.pdf

    Regards
    Richard
     
Loading...
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.