ESSENTIAL WORK OF FRACTURE AND J-INTEGRAL MEASUREMENTS FOR DUCTILE POLYMERS

In the ductile tearing of polymers that neck before failure it is shown that the specific essential fracture work (w(e)), consisting of the energies dissipated in forming and tearing the neck, is a material property for a given sheet thickness and is independent of specimen geometry. Work of fracture experiments using both double deep-edge notched (DENT) and deep-center notched tension (DCNT) geometries with different ligament lengths yielded almost identical w(e) values for a grade of high-density polyethylene. These measurements for w(e) are in fairly good agreement with the theoretical values based on the J integral evaluated along a contour surrounding the neck region near the crack tip. Under J-controlled crack growth conditions, it is shown that J(c) obtained by extrapolation of the J(R) curve to zero crack growth and the slope dJ/da are identical, respectively, to w(e) and 4-beta-w(p) obtained from the straight line relationship between the specific total work of fracture (w(f)) and ligament length (l).