In-plane viscoelasticity of paper in the frequency domain

In this paper a novel experimental set-up for determining the in-plane visc oelastic properties of thin test pieces is presented. The set-up is based u pon biaxial deformation measurements during small uniaxial sinusoidal excit ations of paper strips. In order to do this; a new in-plane deformation tes ter was designed. The set-up enables in-plane viscoelastic characterisation in the frequency range 2.4 . 10(-4) to 10 Hz and is used to examine paper grades typical in offset printing. The results show that the experimental set-up allowed the determination of in-plane viscoelastic properties during a stationary response. This is not the case in traditional set-ups. The dependence of the viscoelastic propert ies on frequency, strain amplitude and static tensile strain was examined. The papers tested exhibited anisotropic frequency dependence on the evaluat ed two-dimensional viscoelastic properties. Finally, the usefulness of empi rical estimates describing the in-plane shear properties was demonstrated i n the frequency domain.