Experimental study of the viscoelastic properties of green poplar wood during maturation

During the radial growth of trees, internal stresses are created because of wood-cell maturation. Biomechanical models can compute these stresses, but they are currently limited by a lack of knowledge about the viscoelastic behavior of green wood. The aim of the present paper is to study the viscoelastic behavior of green wood and to obtain measurements of viscoelastic parameters. In order to accomplish this, the effect of internal maturation stresses on the studied samples was first eliminated by studying viscoelastic phenomena. Creep tests were then performed on small slats of wood using a cantilever bending test. It is shown that green wood viscoelastic behavior can be modeled with Burgers' model. The corresponding parameters are estimated with respect to the wood-cells age. No significant difference between tension wood and normal wood is revealed, but it appears that green wood tends to lose its viscoelastic behavior with maturation