Structural rearrangements during yielding of glassy polymers

Abstract

AbstractThe tensile yield and post yield behavior of polycarbonate (PC) are examined by means of a new experimental device, based on a noncontact measurement of the deformation. This method has the advantage of a detailed measurement of the deformation along the gauge length, which leads to the construction of the true stress‐strain curves of the material tested. Especially in the case of nonuniform deformation, where neck initiation and neck propagation occurs, the correct description of the intrinsic response of the material requires true stress‐strain plots. A viscoplastic model based on the fundamental assumptions of Eyring is used to describe the yield and post‐yield behavior of PC. The strain softening is attributed to a relaxation mechanism that was introduced in previous treatments, and this effect is supported by DSC tests. The theoretical results are compared with the results obtained by an elasto‐plastic model, developed elsewhere, and it is shown that the material follows a viscoplastic path in this deformation procedure.