How Can Poisson's Ratio Reach -1?

[I_am_no1]

v = $$\epsilon$$_trans/ $$\epsilon$$_axial

where

ν is the resulting Poisson's ratio,
$$\epsilon$$_trans is transverse strain
$$\epsilon$$_axial is axial strain
and Poissions Ratio have range and its not more then 0.5 and not less then -1?

so my question is how its value can turn "-1"?

As its already neative and its axial strain or transverse strain one must be negative so the value of Poissions Ratio will turn positive! what do you say!

 

[tiny-tim]

Hi I_am_no1!

These are auxetic materials … see http://en.wikipedia.org/wiki/Auxetic"