Measurement of plane stress essential work of fracture (EWF) for polymer films: effects of gripping and notching methodology

The double-edge-notched-tension (DENT) geometry is widely used in the essen tial work of fracture (EWF) method to measure the plane-stress fracture tou ghness (w(e)) values for ductile polymer film. In the measurement, the liga ment iota has to satisfy the requirement that 3-5t less than or equal to/le ss than or equal to min(W/3.2r(p)). Due to this "valid ligament range" requ irement. different gripping methods may have to he employed for films of di fferent thickness. In this study, the so-called "direct gripping" and "dril led hole gripping" methods were investigated. It was concluded that the w(e ) values were independent of the sample width and the gripping methods. Two different notching techniques were used to pre-notch the specimens, and it was concluded that the same w(e) values were obtained irrespective of the notching method used. Finally, the experimentally measured w(e) for polyeth ylene terephthalate glycol (PETG) films of different thickness are in good agreement with the theoretical predicted values. (C) 2001 Elsevier Science Ltd. All rights reserved.