Modelling the elastic properties of softwood

Abstract

of Holz als Roh-und Werkstoff 56 (1998) 43-50 9 Springer-Verlag 1998 softwood Numerical Finite Element models are presented which relate the macroscopic elastic properties of softwood to local cell characteristics such as cell size, wall thickness, moisture content and microfibril angle. Preliminary results show good agreement with reported values. The model is used to assess the effects of $2 microfibril angle and spiral grain on orthotropic wood stiffness, and to predict the stiffening effect of latewood bands. Simulieren der elastischen Eigenschaften yon Nadelholz-Teil Ih Die zelluliire FeinstrukturDer Beitrag pr/isentiert numerische FE-Modelle, welche die makroskopischen elastischen Eigenschaften yon Nadelholz auf lokale Zellmerkmale wie Gr6fle, Wanddicke, Feuchte und Winkel der Mikrofibrillen zurfickffihren. Erste Ergebnisse zeigen gute Obereinstimmung mit Literturwerten. Mit Hilfe des Modells wird der Einflulg des Winkels der Mikrofibrillen in der $2 und der Faserorientierung auf die Biegesteifigkeit des Holzes abgesch~itzt sowie ein Versteifungseffekt der Sp~itholzzonen vorhergesagt.

Changes in viscoelastic vibrational properties between compression and normal wood: roles of microfibril angle and of lignin

“…On the contrary, the relationship between E'/1 and MFA (Figure 5b) is classical and its shape is very similar to that of previous results (e.g. Norimoto et al 1986;Koponen 1989;Astley et al 1998;Yamamoto and Kojima 2002;Bergander and Salmén 2002;Xu and Liu 2004). Empirical constants for the curve shape described by Eq.…”

“…Axial vibrational properties of wood (specific modulus of elasticity -E/1 and damping coefficient -tan2) are theoretically independent of specific gravity and shall be proportional to cell wall properties.3 Microfibril angle (MFA) is the main parameter influencing E/1 in the wide range of observed MFA values. Various models have been developed to describe this dependency (Norimoto et al 1986;Koponen et al 1989;Astley et al 1998;Yamamoto and Kojima 2002;Bergander and Salmén 2002;Xu and Liu 2004). Although models differ in their formulation, the relationship between E/1 3 and the MFA 3 3 has a more or less sigmoid shape, which can be approximated by: …”

Variation in Mechanical Properties within Individual Annual Rings in the Resonance Spruce Wood (Picea abies (L.) Karst.)

“…McMillin, 1973;Donaldson, 1992;Evans et al, 2000) have reported that MFA decreases with increasing height of the tree, increase in wood density and low rate of growth of trees. Therefore, in modeling the mechanical properties of wood, as well as its moisture deformation, not only the wood density and its microstructural parameters (shape and size of the cells) are taken into regard, but also the arrangement of microfibrils in the cell wall (Mark, 1967;Cowdrey and Preston, 1966;Cave, 1968Cave, , 1969Astley et al, 1998;Xu and Liu, 2004;Mishnaevsky and Qing, 2008). All these factors are refl ected in the acoustic properties of wood.…”

Accuracy of regular wood cell structure model

“…In order to form a sample of softwood for modeling purposes, several options have been proposed in studies by Astley et al (1998) and Persson (2000). In this study, the starting point for the process is the binarization of the actual Norway spruce images.…”