PoissonsRatio:

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   Returns Poisson's ratio.
   If no arguments are entered it will return a list of materials.

   Since version 9.
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   Form:
                PoissonsRatio
   nu = PoissonsRatio( material )
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   Inputs
   ------
   material (1,:) Material string.

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   Outputs
   -------
   nu       (1,:) Poisson's ratio 

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