Essential Work of Fracture for Damage Modeling of Polymer Membranes

Abstract

The specific essential work of fracture for thin biaxially-oriented polyethylene terephthalate, (Mylar), is measured using double-edge notched (DENT) specimens loaded in a uniaxial tension test. Experiments were performed on DENT specimens with varying ligament lengths. Three different thicknesses of Mylar were tested: 25.4 µm (1 mil), 50.8 µm (2 mil), and 76.2 µm (3 mil) Mylar. Load vs. displacement graphs were formed, and from them the area under the curve, or strain energy, was determined. Energy terms were normalized, and then plotted versus ligament length. Specific essential work of fracture values were determined to be 37.027 kJ/m 2 for the 25.4 µm specimens, 36.974 kJ/m 2 for the 50.8 µm specimens, and 36.853 kJ/m 2 for the 76.2 µm specimens. The specific essential work of fracture values were nearly identical for the three separate thicknesses, and therefore is indeed a material property of the Mylar itself. In a companion paper [1], the specific essential work of fracture is then used in a finite element model to predict the tearing response of polymer sheets.