High-Temperature large-strain behavior of polycarbonate, polyetherimide and poly(butylene terephthalate)

A noncontacting experimental procedure has been used for characterizing the high-temperature large-strain uniaxial behavior of polycarbonate (PC), polyetherimide (PEI), and poly(butylene terephthalate) (PBT), through controlled tests on flat specimens cut from extruded sheet. While each of these polymers exhibits stable necking over a broad temperature range, the transition to the necked state is shown to be more gradual at higher temperatures, resulting in a less sharply defined neck transition region during the drawing process. These trends in necking behavior, and other phenomena such as double necking, which only occur at high temperatures, are illustrated through contour plots of the Cauchy-Green deformation tensor. Elevated temperature true-stress versus stretch data are given for each of these polymers.