STABLE CRACK-GROWTH IN DUCTILE POLYMERS

Growth of a crack in ductile polymers (polyarylate, PTFE, and PU/PMMA blends) was studied. The crack growth was described assuming that loca l yielding in the crack tip is similar to large-scale shear yielding i n rigid-plastic materials. Crack growth was stable, and a wedge shaped crack tip was formed. The crack tip opening displacement and the crac k extension in the initial stage of the crack growth were proportional to the square of the strain up to 11% elongation. Dugdale's equation was modified to describe the magnitude of the crack tip opening. In PA , a yield subzone near the crack tip was observed.