Volume 18, Issue 1 (January 1990)
Applicability of Modified J as a Fracture Parameter for Polycarbonate
The applicability of modified J-integral, JM, as a fracture parameter for plain and impact-modified polycarbonate was examined. Specific issues were:
1. Influence of the non-unique tensile stress-strain behavior, which is characteristic of these materials, on the applicability of JM.
2. Methods of estimating JM in fracture specimens given the load—load-point deflection diagram.
3. Fracture mechanisms that cause ductile and brittle crack growth in this class of materials.
Crack growth resistance (JM-R) curves were obtained from compact-type (CT) specimens of multiple sizes and specimens of another geometry (single edge notch [SEN]). The JM-R curves were consistent for crack extensions up to 2.5 mm for CT specimens of various sizes and were independent of geometry for crack initiation and a limited amount of crack growth (1.5 mm). The JM-R curve for toughened polycarbonate showed a considerably higher resistance to ductile tearing than that of the plain polycarbonate. The fracture mechanisms in both types of materials were characterized using a scanning electron microscope.