How to Eliminate Buckling in the Essential Work of Fracture Measurement with Very Thin Plastic Films

摘要

When the Essential Work of Fracture (EWF) method is used to evaluate the fracture toughness of ductile thin polymer films, buckling phenomenon is very often observed, which may violate the conditions for data validity. In some cases, buckling is so severe that to perform a valid EWF test is virtually impossible. In this work, we propose an experimental set-up using U-shaped fixture to eliminate the buckling problem in thin film EWF tests with double-edge notched specimen (DENT). The influences of the U-clamp on the yielding, plastic zone development, crack initiation and propagation behaviors of the thin film samples were examined by experiments as well as finite element analysis. The results demonstrate that the use of the newly designed U-clamp has little effect on the fracture behavior of the tested thin polymer films. Therefore, it is an ideal set-up for the EWF measurements with very thin films when buckling is a problem.