Abstract
For the vulcanized natural rubber stretched to a rupture, the change of Poisson's ratio is investigated by measuring the surface strain in longitudinal and lateral directions.
The results are summarized as follows :
(1) It is correct to take the Poisson's ratio as 0.5 when the deformation is infinitesimal at an instant of stretching. But if the deformation reaches some finite value the Poisson's ratio is decreased from 0.5 with an increasing deformation value. The former Poisson's ratio is named here the instantaneous Poisson's ratio and the latter the apparent Poisson's ratio.
(2) Both Poisson's ratios mentioned above don't vary with the same extension even when the carbonblack contents are varied and the extension is repeated.
(3) Apparent Poisson's ratio is measured on the assumption of arbitrary extension.
In an experimental expression the apparent Poisson's ratio is estimated as a function of the elongation ratio.
