On the basis of Lederman′s model

the strain rate dependent constitutive relation of open cell foam plastics is derived by supposing the matrix material to be Voigt′s visco elastic body.By means of the constitutive relation

the dependence of some mechanical properties of foam plastics on the strain

strain rate and parameter of cell structure is investigated in this paper.The results have shown that the decrease of Poisson′s ratio of foam plastics is more obvious with the increase of strain rate than the one with the change of other two factors.In addition

the Young's modulus of foam plastics is reduced by introducing viscous effect.