On the plane-strain essential work of fracture of polymer sheets

Abstract

The essential work of fracture (EWF) is the most straightforward method to assess the toughness of ductile polymer films and sheets in which per se plane-stress conditions prevail. The interest is focused, however, on the determination of the plane-strain fracture toughness being a material parameter. It was demonstrated that the plane-strain essential work of fracture (determined in dynamic tensile impact tests) agreed well with that of the yielding-related specific essential work of fracture concluded from static mechanical tests for an amorphous copolyester sheet. This agreement still held when the plane-strain essential work of fracture derived by considering the experimental data in the plane-stress/plane-strain transition range (laying below the lower threshold ligament for which a linear regression was adopted) for a thicker sheet of the same polymer has been considered.