The curl and fluting of paper : The effect of elasto-plasticity

An in-plane elasto-plastic material model and a hygroexpansivity model were ap­plied for paper. The input parameters for both models are fiber orientation and dry solids content. A finite element model was constructed offering possibilities for studying different structural variations of an orthotropic sheet as well as buckling behavior and internal stress situations under through-thickness strain differences. Examples related to the curl and web­fluting phenomena of paper are presented. Both studied cases presented in this paper indicates the usefulness of the hygro-elasto-plastic model in predicting the challenging deformation phe­nomena of orthotropic paper sheets. The application possibilities of the hygro-elasto-plastic model are diverse, including the investigation into several phenomena and defects appearing in drying, converting and printing process conditions.