The Yield Behaviour of Rigid Polymers

The yield behavior of solid polymers has been examined, with especial reference to that of the glassy amorphous polymers. Considering polymethyl methacrylate to be a typical glassy amorphous polymer, the effects of strain rate and temperature on the yield stress have been determined by taking stress- strain curves in simple plane strain compression. The variation of the plane strain compressive yield stress with applied tension and compression has also been determined for polymethyl methacrylate and several other polymers. It was shown that the hydrostatic component of stress had a significant effect on the yield behavior of the polymers studied. This has been considered in terms of the Tresca and von Mises yield criteria modified for pressure dependence.