Study of Delamination and Buckling of Paper during the Creping Process using Finite Element Method -- A Cohesive Element Approach

Paper variants such as paper napkins, tissue paper are manufactured by a process called as creping during which a paper adhesively bonded to a rotating drum is continuously scraped off by a blade. Resulting low density paper provides critical attributes such as fluid absorbency, softness, and stretchiness to the final paper product. The macroscopic effect of creping is the formation of fine ridges called as " crepes". The quality of the final product is characterized by the length of the crepes. The process of creping has been hypothesized to be a periodic sequence of delamination, buckling and post-buckling compression of paper. A quasi-static comparison of a two dimensional finite element model implementing surface based cohesive zone theory and a critical stress criteria based fracture model is presented. The adhesive being a critical part of creping is represented by a zero thickness cohesive layer in the cohesive model . A comparison of a 1-D analytical model implementing an energy release rate approach and a Virtual Crack Closure Technique (VCCT) quasi-static finite element model is presented. An experimental investigation to quantitatively determine the adhesive fracture toughness during creping is conducted by an energy based approach. The influence of drum speed and adhesive concentration on the adhesive fracture energy is analyzed and comparison with a dynamic finite element model is obtained.