Essential work of fracture

Publisher Summary This chapter describes the different aspects of the essential work of fracture (EWF). There is increasing use of the EWF method to determine the toughness of thin plastic films. There are a number of potential areas for use of this technique, such as in the measurement of the fracture toughness of thin coatings and paints and the study of packaging properties. The EWF approach is a means of partitioning the energy associated with a fracture into two parts. One element is specific to the fracture of the material and, as such, is a material parameter. The second element is related to gross plastic deformation and depends upon the geometry of the fractured specimen or component. The principle of the technique is to measure the load-displacement trace, and hence the energy to fracture for a series of fracture specimens, ensuring that plasticity in the ligament is fully developed. In such cases, it is possible to partition the work of fracture into an element taking place along the fracture line and another element taking place in a volume of material surrounding the crack. The former element is proportional to the fracture area, and hence the ligament length, while the latter element is proportional to the volume of the outer region.