A unique set of double-edge notched tension specimens of a Polyethylene Terephthalate Glycol-modi¿ed ¿lm was tested in mode I, plane stress. The load was registered on a universal testing machine. The displacements, ligament lengths, and video frames were recorded by a Digital Image Correlation system. With these registered data, the essential work of fracture, J-integral, and crack tip opening displacement (CTOD) fracture concepts have been applied. The onset of crack initiation was through a complete yielded ligament. The analysis showed that the intrinsic speci¿c work of fracture, we, is the speci¿c energy just up to crack initiation, which is an initiation value. we has both a coincident value and the same con-ceptual meaning as Jo, the J-integral at the onset of crack initiation. The relationship between Jo and CTOD is also determined. The in¿uence on the notch quality when the specimens were sharpened by two different procedures, femtosecond laser ablation and razor blade sliding, was analysed in detail.

Peer Reviewed