Void Growth in Viscoelastic Polymeric Materials

An incremental scheme governing the transient and self-similar void growth of aligned spheroidal voids in a linear viscoelastic polymeric material under both the stress and strain-rate controls is developed for a class of linear viscoelastic polymeric materials at low concentration and moderate strain. The theory is based upon Eshelby-Mori-Tanaka’s concept in elasticity, but extended to the viscoelastic media by the Laplace transform and developed in a way suitable for the calculation of void growth. The conditions of void growth with constant porosity under both the stress and strain-rate controlled processes are established, and it is found that under the former process this condition is only dependent on the void shape and the Poisson ratio of the polymeric material, but under the later one it is also dependent upon the porosity of the material. The theory is then applied to calculate the transient void growth under axisymmetric triaxial loading, and the corresponding changes of the void shape and porosity are examined to uncover the influence of triaxiality.