On the thermomechanical behaviour of polymeric sheets at localized necking

Polymeric materials are among the most widely used materials in modern industry. Their advantages, including lightweight properties, high corrosion resistance, and excellent thermal and electrical insulation, have garnered significant interest from researchers aiming to precisely determine their formability characteristics. Consequently, numerous studies in the literature focus on characterising their forming limits through necking and fracture, employing techniques derived from Digital Image Correlation (DIC), originally developed for sheet metal forming. This study proposes a less explored approach, which is based on the analysis of the temperature gradients on the surface during deformation by Digital Infrared Thermography (DIT). A series of stretching tests were conducted at room temperature on 1.5 mm thick polycarbonate sheets. Strain-based approaches currently established in the literature were applied to determine the onset of necking in the specimens. The thermal behaviour observed during the onset and subsequent stable propagation of necking in the polymeric sheet is evaluated. The analysis of 3D temperature profiles on the specimen surface provides insight into the heat generated by plastic deformation and the influence of heat transfer mechanisms during the necking development.