The Effect of Fibre Orientation Streaks on Out-of-plane Instabilities in Paper

Variations in in-plane fibre orientations have been discussed as a possible reason for out-of-plane distortions in paper, such as cockling and fluting. Irregularities in fibre orientations can potentially result in local strain variations during tensioning or moisture change, and thus can cause local buckling in paper. In this work, the impacts of the fibre orientation on out-of-plane instabilities in paper were systematically examined with the help of non-linear finite element analyses. In the simulation local variations in fibre orientation were introduced artificially as streaks in the machine direction (MD). Such streaks can appear in a real paper due to cross flows of jet originated from headbox, for example. The results of this work suggest that the fibre orientation streaks surprisingly have a limited effect on out-of-plane instabilities in paper, as compared with the local moisture variations that the authors investigated previously.