Nomenclature a crack length cte constant CTOD crack tip opening displacement d displacement DENT double edge notched tension specimen DIC digital image correlation system The post-yield fracture of a ductile polymer film: Notch quality, essential work of fracture, crack tip opening displacement, and J-integral A.B. Martínez N. León ⁎ noel.leon@estudiant.upc.edu D. Arencón M. Sánchez-Soto Centre Català del Plàstic, Departament de Ciència dels Materials i Enginyeria Metal-lúrgica, Universitat Politècnica de Catalunya-Barcelona TECH, C/Colom 114, 08222 Terrassa, Spain ⁎ Corresponding author. Abstract Double edge notched tension (DENT) specimens of a polyethylene terephthalate (PET) film were tested in an universal testing machine, measuring the displacements and the ligament lengths with a digital image correlation (DIC) system. With these data the essential work of fracture (EWF), crack tip opening displacement (CTOD), and the J-integral fracture methods were compared. The specimens were tested in mode I under plane stress conditions, verifying that the crack always propagated through a fully yielded ligament. It has been proved that w e , the specific essential work of fracture was the specific energy just up to crack initiation and has the same value that J-integral at crack initiation, J o . The relationship of these parameters with the CTOD was also shown. The influence of the notch quality on the fracture behaviour when the specimens were sharpened by two different methods, femtosecond laser ablation or by razor blade sliding, has also been analysed in detail. Keywords: Essential work of fracture; Crack tip opening displacement; J-integral; Polymer film; Femtolaser