Comments on the experimental methodology for determination of the hygro-mechanical properties of wood

Abstract

When wood is subjected simultaneously to load and moisture content changes below the fiber saturation point, the mechano-sorptive effect may be observed as an additional deformation that cannot be attributed to simple superposition of elastic deformation, free shrinkage or swelling, or creep in steady climate conditions. The phenomenon has been subject to research for more than half a century. Although numerous mathematical models and detailed theoretical descriptions have been proposed over time, the basic mechanism of mechanosorption has remained unclear, the experimental data are scattered and lack logical classification, and the experimental determination of its basic parameters on a material level, understood as a local property decoupled from artifacts of the testing protocol, remains a serious challenge. In this paper basic requirements for adequate experimental methods for comprehensive determination of the mechano-sorptive behavior of wood are proposed and briefly discussed. The principal requirements are that the experimental research on mechano-sorption is focused on the material level properties and elementary loading modes (tension and compression); that proper attention is paid to the effect of changing distribution of moisture content within the tested volume; and that the tests are designed so that a comprehensive separation of strain components is enhanced.

Elastic properties of adhesive polymers. III. Adhesive polymer films under dry and wet conditions characterized by means of nanoindentation

“…Bond performance, in contrast, was better for PF‐bonded particleboards under both dry and wet conditions. Muszynski et al10 found the mechanical properties of phenol resorcinol formaldehyde (PRF) adhesive films to be highly sensitive to changing moisture contents in comparison with other adhesives. The high durability of PRF bonds was explained by the fact that the hygromechanical properties of the adhesive and wood were at comparable levels in the case of PRF.…”

Orthotropic hygro-mechanical behavior of Chinese fir during cyclical relative humidity variation

“…So far, comprehensive data comprising the MC-dependent orthotropic MS behavior is missing. While the influence of MC on the MS behavior of wood in the longitudinal (L) direction is relatively well known [8,[14][15][16][17][18], the behavior in the perpendicular to the grain (radial, R and tangential, T), remains underexplored [19][20][21][22][23]. As tensile stress perpendicular to the grain represents the weakest timber point, its knowledge, especially as it relates to load capacity and failure prediction of wooden structures, is highly important in wood engineering.…”

Investigation of oscillating climates for wood drying using the flying wood test and loaded beams: need for a new mechano-sorptive model

“…The proposed models aim to fulfill many requirements listed by Grossman (1976). In spite of this, the determination of the model parameters from experimental results remains a serious Universidad del Bío -Bío challenge because of the coupled phenomena and the artifacts of the testing protocol (Muszynski et al 2005). This is probably the reason why the simplest mechano-sorptive models, such as those of Ranta Maunus (1975), Salin (1992) or Leicester (1971), are usually embedded in drying codes (Figure 1).…”