THE ESSENTIAL WORK OF PLANE-STRESS DUCTILE FRACTURE OF POLY(ETHER-ETHER KETONE) THERMOPLASTIC

The total work of fracture in a ductile material is not a material constant and the linear elastic fracture mechanics is not appropriate. Only the work performed per unit area in the fracture process zone, called the specific essential work of fracture, is a material constant for a given specimen thickness. The results of an experimental investigation on the essential work of fracture of a crystalline and a non-crystalline poly(ether-ether ketone) (PEEK) films are reported. Single-edge notched specimens were used to determine the specific essential work by extrapolating the straight-line relationship between the specific work of fracture and ligament length to zero ligament length. In this way, the specific essential work of fracture for the crystalline PEEK film of thickness 0.1 mm was measured to be 65.02 kJ m-2 and for the non-crystalline film of thickness 0.25 mm was measured as 62.71 kJ m-2. Advancing crack opening displacements (COD) have also been analysed and the specific essential work of fracture calculated from the COD values compared extremely well with those results obtained from the intercept of specific work of fracture versus ligament length.