Modelling the transverse viscoelasticity of green wood using a combination of two parabolic elements

The rigidity in radial compression at different levels of temperature and strain rate have been measured on green Boco, with a drastic softening around 60degreesC attributed to the glassy transition of lignin. The representation of experimental results in an approximated complex diagram revealed a secondary viscoelastic process occurring at lower temperature. A multiparabolic model was used for the analysis. For convenience, each parabolic element was replaced by a generalised Maxwell model with a modified-Gaussian relaxation spectrum. This model fitted correctly the observed behaviour of wood in the time range of 0.05 to 50 sec and temperature between 10 to 90degreesC.