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Homework Help: Shear modulus of dry spaghetti

  1. Sep 8, 2012 #1
    While doing an assignment on building with spaghetti I have come across the shear modulus. I need to find the shear modulus in order to use the torsion equation. Does anyone have a value for it by any chance?
  2. jcsd
  3. Sep 8, 2012 #2
    Just poking around the internet, the values for Young's modulus vary, especially depending on moisture content.

    http://books.google.com/books?id=WK..."modulus of elasticity" for spaghetti&f=false

    Shows that at 10% moisture, E=1E6 PSI.


    Lists it at 1E9 Pa, which is in the same range as the other article.

    Most solids are known exhibit Poisson ratios of 0.25-0.35 and taking the middle ground here and assuming v=0.30 for dry spaghetti, you can reach a rather raw approximation by using:


    Solving for G with the assumed values would give you G=400 MPa= 58 ksi

    As you can see I've left out any decimal expansion to indicate the lack of accuracy with these values but seeing as torsion doesn't seem to come into play much with spaghetti, I think your best bet is to experiment around with some values in that range to see what works. I think however that since dry spaghetti is most obviously brittle you'll more wiggle room since brittle materials tend to fail in high tensions cases.
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