Glassy polymers dilatant plasticity

A further important effect of the plastic response of glassy polymers is a prominent strength-differential (SD) effect, which is a consequence of the usual dilatant character of an ST whereby the transformation shear strain is generally kinematically associated with a coupled transformation dilatation e, as discussed earlier. This transformation dilatation interacts strongly with a mean normal stress, (7n, when one is present, i.e., with pressure in compression flow and negative... 

Ideally, crazing is a form of plastic deformation of a linear-chain glassy polymer whereby under a tensile stress a slender polymer layer undergoes a uniaxial planar dilatational transformation ej producing a uniaxial strain c in the direction of the tensile stress, in proportion to the volume fraction c of transformed polymer, i.e.,... 

A. S. Argon, Physical Basis of Distortional and Dilatational Plastic Flow in Glassy Polymers , J. Macromol. Sci., Phys. B8, 573-596 (1973). 

It is well known that the mechanical behavior of glassy amorphous polymers is strongly influenced by hydrostatic pressure. A pronounced change is that polymers, which fracture in a brittle manner, can be made to yield by the application of hydrostatic pressure Additional experimental evidence for the role of a dilatational stress component in crazing in semicrystalline thermoplastics is obtainai by the tests in which hydrostatic pressure suppresses craze nucleation as a result, above a certain critical hydrostatic pressure the material can be plastically deformed. 

---