Crack-tip characterization in paper

The application of fracture mechanics to paper and paper structures is of fundamental interest. In the problem of web breaks in printing plants, there is also an immediate application. The aim of this work was to review classical fracture mechanics and its use in problems involving paper. Constitutive relations were discussed and an orthotropic elastic-plastic constitutive relation for paper was proposed and used to determine the J integral as a crack-tip parameter in the case studied, i.e. an infinite strip with a semi-infinite crack. This geometry, with prescribed edge displacements, is related closely to many finite paper structures. A closed-form solution for the infinite strip model was compared with numerical computations to establish its validity. Numerical methods (FEA) were also used to calculate the J integral in the case of finite geometries, and the geometry factors for the geometries studied in this work were stated.