Abstract
In this paper, the relation between the anatomical features and the elastic anisotropy in the transverse direction of softwood was investigated experimentally and numerically by using a simple model.
The cell arrangement in the cross section of wood was approximated by two kinds of porous models, which were made of an isotropic and homogeneous material. They corresponded to earlywood and latewood. Tensile tests were carried out in various directions between the two principal axes of these models. Then, the numerical values of n, which is an index of anisotropy decided by both the geometrical features of deformable unit of wood and its volume fraction, were determined. The modulus of ray tissue was calculated using the anatomical model of its fine structure.
On the basis of these experimental and calculated data, the elastic moduli in various directions of whole wood were simulated by considering wood as a complex laminate with two stages of lamination, i. e. a laminate of alternating layers of transversely anisotropic earlywood and latewood perpendicular to ray tissue. The mixture rule was used in order to compute the elastic modulus of this complex laminate. Young's modulus perpendicular to the grain of sugiwood and hinokiwood at any given angle to the radial direction was obtained by measurements with special u-gages designed to eliminate various errors.
From these results, it was found that the elastic anisotropy of wood was caused predominantly by the arrangement of pores and macroscopically laminated structures.
