Shear Deformation under Hydrostatic Pressure of Polytetrafluoroethylene and Polycarbonate
In a previous study, the dependence of the shear stress-strain behavior of two polymers, polyoxymethylene (POM) and polypropylene (PP) on hydrostatic pressure was well documented [l]. Furthermore, at a critical shear strain of 0.500, both polymers exhibited a region of concentrated shear strain (girdle) in the central portion of the test specimens. Evidently, instabilities similar to those usually observed in tensile specimens (necking) may also develop in highly deformed torsion specimens. Other researchers have reported the pressure dependence of the shear modulus and the shear yield stress of polymers, but none has reported observing a girdle [2–5]. This study was directed toward the investigation of the pressure-dependent shear stress-strain behavior of two diverse polymers; namely, highly crystalline polytetrafluoroethylene (PTFE) and completely amorphous polycarbonate (PC). In addition, physical changes in the specimens were monitored to ascertain the generality of the shear strain girdle as a manifestation of shear yielding in these materials.
KeywordsShear Modulus Hydrostatic Pressure Shear Strain Shear Deformation Shear Yield Stress
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