The constitutive response of glassy polymers is characterized by their complex thermo-mechanical behavior such as strain rate and temperature sensitive yielding, softening at small strains and re-hardening at large strains. These complex behaviors trigger strain localization in the deformation of polymers. Since localization can be induced by both structural and material instabilities, careful analysis needs to be performed to investigate the localization behavior of polymer specimen testing. Localization such as neck formation and propagation that typically occurs in the tensile and compressive testing of polymers and plastics makes it difficult for experimentalists to extract their intrinsic constitutive response. This problem is exacerbated when localization occurs with shear bands. In this study, a macromolecular constitutive model for polymers showing small-strain softening and large-strain directional hardening is employed to investigate the effect of localization in tension onto the constitutive identification process. Considering the complex interplay between the structural and constitutive instabilities, a method based on direct, real-time measurement of area reduction at the neck section has been proposed to extract the intrinsic constitutive response of polymer materials.

This content is only available via PDF.
You do not currently have access to this content.