The role of water in the behavior of wood

Abstract

Wood, due to its biological origin, has the capacity to interact with water. Sorption/desorption of moisture is accompanied with swelling/shrinkage and softening/hardening of its stiffness. The correct prediction of the behavior of wood components undergoing environmental loading requires that the moisture behavior and mechanical behavior of wood are considered in a coupled manner. We propose a comprehensive framework using a fully coupled poromechanical approach, where its multiscale implementation provides the capacity to take into account, directly, the exact geometry of the wood cellular structure, using computational homogenization. A hierarchical model is used to take into account the subcellular composite-like organization of the material. Such advanced modeling requires high resolution experimental data for the appropriate determination of inputs and for its validation. High-resolution x-ray tomography, digital image correlation, and neutron imaging are presented as valuable methods to provide the required information

Factors affecting the hygroexpansion of paper

“…Generally, all publications agree that a higher MFA leads to higher hygroexpansion in the longitudinal direction and lower hygroexpansion in the transverse direction of the fiber [47,52,97,98,99,100]. For small MFAs (\30°), the longitudinal shrinkage is a lot smaller (\1%) than the transverse shrinkage (7-9%), but in the region of extremely large MFAs (40°-50°) this relation switches and the longitudinal shrinkage (\8%) is larger than the transverse shrinkage (\4%) [71].…”

“…of diffuse character'' [45]. The importance or unimportance of this inter-layer for the hygroelastic properties is addressed by Wang et al [46] and Derome et al [47] as well as in section ''Microfibril angle''. The following subsections discuss the effect of the single polymers (cellulose, hemicelluloses and lignin), the microfibril angle, the fiber morphology and sorption on the hygroexpansion of single fibers and paper sheets.…”

“…The exact relative amount of crystalline and amorphous cellulose depends on the species [69]. Compared to lignin and hemicellulose, cellulose is a rather crystalline material and therefore its swelling capability-determined by the amorphous regions-is low and sometimes neglected when talking about fiber hygroexpansion [46,70,71] or homogenized with the swelling capability of hemicelluloses [47]. However, only 60-70% of the cellulose in cell wall layers exists in a crystalline form.…”

Mechanical Properties of Norway Spruce: Intra-Ring Variation and Generic Behavior of Earlywood and Latewood until Failure

“…On the growth ring scale, the structure of softwoods with their alternating high-density latewood (LW) and low-density earlywood (EW) bands (e.g., Lanvermann et al 2013b) adds a further level of complexity. The different tissues exhibit different transverse physical properties with respect to moisture-induced deformation (Derome et al 2011;Derome et al 2013Keunecke et al 2012Rafsanjani et al 2012) and mechanical properties as derived from simulations (Kahle and Woodhouse 1994;Modén and Berglund 2008b;Persson 2000;Rafsanjani et al 2012). Due to its hierarchical structure, it is evident that the macroscopic behavior originates from features on a microscopic scale.…”

Moisture Research in the Field of Architecture, Japan

“…Considering the progress of computing speed and memory capacity of computers, it is desirable to perform research on the direct computation of material properties and HAM transfer, which considers the micro structure of the porous material (Derome 2012), and avoid simplifications as far as possible.…”