The Poissons ratio of an isotropic viscoelastic solid is time dependent  as are the other material functions such as the tensile and bulk relaxation moduli. This matrix
time-dependent behavior of the Poissons ratio has a significant effect on certain micromechanical predictions of composite viscoelastic relaxation. Yet, experimental
characterization of the viscoelastic Poissons ratio is quite difficult, requiring the measurement of at least two independent viscoelastic functions. Furthermore,
simultaneous measurement of these functions gives more accurate results since derivative properties can be calculated without introducing errors due to
specimen and environmental variation.
Although a wealth of data have been collected on the viscoelastic response of polymers in shear and extension, data on the time dependence of the Poissons
relaxation of polymers are lacking. Several studies present time-dependent Poissons ratio data. However, the data are limited to low temperature , large strains , or the experimental technique is applicable to only certain materials . An early work by  presents only instantaneous values for the Poissons
ratio of polymers at large strains.
Pages : 13
Size: 1.04 mb
Author : D.J. OBrien, N.R. Sottos , S.R.White
Cure-dependent Viscoelastic Poissonís Ratio of Epoxy