Über den Einfluß von Scherbändern auf den Bruch in Polystyrol

Abstract

During the compressive deformation of atactic Polystyrene coarse shear bands and/or diffuse shear zones are formed according to the testing conditions. Optical and scanning electron micrographs of these deformation zones and of the resulting fracture surfaces are presented in this paper. With these observations the processes which occur during fracture in the different shear zones can be interpreted.

In spite of a macroscopically brittle fracture in the discrete coarse shear bands fine stretched fibrils are found on the fracture surface. They indicate large plastic deformations inside the shear bands before final fracture occurred. From these observations a similarity of the fracture mechanisms in coarse shear bands and crazes of Polystyrene can be deduced.

When the plastic deformation only occurs in a broad diffuse shear zone, for example at elevated temperatures, ductile fracture behaviour is observed. In this case the deformation develops by void- and craze-formation and by viscous flow in a large volume of the polymer.