Young's Modulus of Cell Wall for Coniferous Wood

Abstract

Young's modulus of the cell wall in longitudinal direction, which varies widely not only among the different wood species but also within the same species, is closely related to the bending quality of wood. In order to explain this observation, we made measurements of Young's modulus, crystallinity and microfibril angle for numerous softwood species. The experimental values of the average dynamic Young's modulus of the cell wall ranged from 4.5×1011dyn/cm2 to 6.4×1010dyn/cm2. Species having extremely low value of this modulus showed low degree of crystallinity and large microfibril angle. On the other hand, the Young's modulus of the cell wall was theoretically estimated using a cell-wall model, in which the distribution of chemical constituents and microfibril angles in the cell-wall layers are taken into account. The effects of crystallinity, microfibril angle and elastic constants of matrix on the Young's modulus of the cell wall was examined according to this theory. From these results it was proved that the Young's modulus of the cell wall depend strongly on microfibril angle and that the main reason for the variation of the Young's modulus of the cell wall and the bending quality among the different species is resulted from the variation of microfibril angle.