Failure Behaviour of Paper Sheets

ABSTRACT: An experimental analysis was undertaken to establish the failure strengths in tension and compression along the strong direction (machine direction) and the weak transverse plane of isotropy (cross direction) for a typical paperboard. The principal strengths of the material along the strong machine direction and on the transverse plane which may be assumed to be approximately isotropic allowed the possibility of forming the elliptic paraboloid failure locus corresponding to this type of material. It was shown that papers in general are tension strong materials having the infinite part of their parabo-loid failure surface turned toward the tension-tension-tension octant in the principal stress space. Finally, attempts to use different strengths along the isotropic plane in order to represent the material as fully orthotropic indicated that there are only small changes in the failure locus due to the changes of the intermediate failure strengths. This implies that the simplified assumption that papers sheets may be considered as transversely isotropic materials is a satisfactory approximation