Applicability of Anisotropic Viscoelasticity of Paper at Small Deformations

In this paper the applicability of two-dimensional phenomenlogical linear viscoelastic modelling aimed at printing applications is presented. An iterative algorithm is used to find model parameters evaluated from dynamic mechanical testing at stationary conditions. Experiments are performed in the time domain with different load stimuli in either displacement or force control. The experiments are compared to model predictions.The results show that only small deviations were found on model parameters from the algorithm used on either the loss or the storage properties of paper. This was illustrated by converting line spectra from storage compliances to loss compliances within the frequency domain. The harmonic properties were obtained at conditions with nonlinear material behaviour. Despite this, the two-dimensional linear viscoelastic model described well the behaviour of paper at different states of stress and strain at levels adequate for web-fed printing. The usefulness of the relation between retardances and relaxances was examined by comparing model predictions with different driving stimuli resulting in either creep or relaxation. The time-dependent transverse strain of machine-made paper due to either longitudinal stress relaxation or creep was demonstrated. Finally, extensions of the present model including inelastic material behaviour were discussed.
QC 20111129