Macroscopic yield in cavitated polymer blends

Localized plastic deformation in ternary polymer blends

“…The isotropic elasticity tensor for the porous material is now given in terms of effective elastic constants E à ðf Þ, m à ðf Þ, depending on the porosity f. Respective expressions obtained via the Mori-Tanaka scheme can be found e.g. in Pijnenburg and Van der Giessen (2001). With the initial value f 0 representing the rubber content in ABS, the porosity may increase in the course of deformation due to void growth in the plastically incompressible SAN matrix.…”

“…Since then, a number of extensions have been suggested in the literature accounting for more general material behavior. Paying special attention to the effect of non-negligible elastic strains around growing voids in a glassy polymer, Steenbrink et al (1998) and Pijnenburg and Van der Giessen (2001) developed such a model showing much better agreement with cell calculations than the unmodified Gurson model. However, in view of the complexity of this model and of the error made in approximating the cavitated rubber particles as voids, we adopt here an alternative and computationally more convenient approach.…”

“…Because of the intrinsic softening of SAN, plastic flow at the onset of macroscopic yield is not uniform throughout the matrix phase but localizes in the ligament connecting neighboring voids (Pijnenburg et al, 1999;Pijnenburg and Van der Giessen, 2001). Therefore the driving stress of the porous material should (at least initially, i.e.…”

“…To account for this heterogeneous plastic flow, the factor cðf 0 Þ depending on the initial porosity is introduced such that ð1 À f Þscðf 0 Þ can be regarded as the equivalent driving stress of the porous material. For example, choosing cðf 0 Þ ¼ ð1 þ ffiffiffiffi f 0 p Þ À1 for the 2D case of cylindrical voids, the equivalent driving stress for f ¼ f 0 becomes ð1 À ffiffiffiffi f 0 p Þs where 1 À ffiffiffiffi f 0 p is approximately the relative width of the ligament between voids in a square array (Pijnenburg and Van der Giessen, 2001). …”

A novel approach to the analysis of distributed shear banding in polymer blends

“…References [4,10,11]. In such models the rubber particles, once cavitated, are replaced with voids since the rubber modulus is in practice much smaller than that of the matrix.…”