This paper reviews recent findings on wood–water interaction and puts them into context of established knowledge in the field. Several new findings challenge prevalent theories and are critically discussed in an attempt to advance current knowledge and highlight gaps. The focus of this review is put on water in the broadest concept of wood products, that is, the living tree is not considered. Moreover, the review covers the basic wood–water relation, states and transitions. Secondary effects such as the ability of water to alter physical properties of wood are only discussed in cases where there is an influence on state and/or transition.

/pdf/a-critical-discussion-of-the-physics-of-wood-water-1onxyd5jm3.pdf

A critical discussion of the physics of wood–water interactions

A review of structural, thermo-physical, acoustical, and environmental properties of wooden materials for building applications

Today’s materials research aims at excellent mechanical performance in combination with advanced functionality. In this regard, great progress has been made in tailoring the materials by assembly processes in bottom-up approaches. In the field of wood-derived materials, nanocellulose research has gained increasing attention, and materials with advanced properties were developed. However, there are still unresolved issues concerning upscaling for large-scale applications. Alternatively, the sophisticated hierarchical scaffold of wood can be utilized in a top-down approach to upscale functionalization, and one can profit at the same time from its renewable nature, CO2 storing capacity, light weight, and good mechanical performance. Nevertheless, for bulk wood materials, a wider multipurpose industrial use is so far impeded by concerns regarding durability, natural heterogeneity as well as limitations in terms of functionalization, processing, and shaping. Here, we present a novel cellulose bulk material con...

Delignified and Densified Cellulose Bulk Materials with Excellent Tensile Properties for Sustainable Engineering

Heat capacity measurements of various biomass types and pyrolysis residues

Development and performance evaluation of a new thermal insulation material from rice straw using high frequency hot-pressing

Despite the exceptional position of yew among the gymnosperms concerning its elastomechanical properties, no reference values for its elastic constants apart from the longitudinal Young’s modulus have been available from literature so far. Hence, this study’s objective was to determine the Young’s moduli E
 L, E
 R and E
 T and the shear moduli G
 LR, G
 LT and G
 RT of yew wood. For that purpose, we measured the ultrasound velocities of longitudinal and transversal waves applied to small cubic specimens and derived the elastic constants from the results. The tests were carried out at varying wood moisture contents and were applied to spruce specimens as well in order to put the results into perspective. Results indicate that E
 L is in the same order of magnitude for both species, which means that a high-density wood species like yew does not inevitably have to have a high longitudinal Young’s modulus. For the transverse Young’s moduli of yew, however, we obtained 1.5–2 times, for the shear moduli even 3–6 times higher values compared to spruce. The variation of moisture content primarily revealed differences between both species concerning the shear modulus of the RT plane. We concluded that anatomical features such as the microfibril angle, the high ray percentage and presumably the large amount of extractives must fulfil important functions for the extraordinary elastomechanical behaviour of yew wood which still has to be investigated in subsequent micromechanical studies.

/pdf/determination-of-young-s-and-shear-moduli-of-common-yew-and-3mws9op5sp.pdf

Determination of Young’s and shear moduli of common yew and Norway spruce by means of ultrasonic waves

Knowledge of wood aging and the property changes of aged wood compared with recent wood are crucial for conservation of wooden cultural heritage objects and historic buildings constructed of wood and also for the reuse of old construction wood. Therefore, a thorough literature review is presented about the different aspects of wood aging to provide a database for further investigations. One focus lies on the different kinds of aging: natural aging under aerobic and anaerobic storage conditions in contrast to accelerated aging under heat treatment. Further, influencing factors like wood treatment and long-term loading on the aging process are discussed. Property changes of naturally aged wood that has been stored under aerobic conditions are also researched. The resulting chemical, physical, and mechanical changes are thus discussed as well as any changes in color.

Effects of aging on wood: a literature review

Holzphysik: Physik des Holzes und der Holzwerkstoffe

For several wood-based materials (plywood, OSB, melamine faced board (MFB), particle board and fibre
 board), the thermal conductivity was determined as a function of the temperature (ranging between 10
 and 30 °C) and also the moisture content (from an oven-dry sample up to a moisture content
 at 80% RH). Furthermore, the water vapour resistance factor of these materials as well as of the coating
 (at MFB) and the diffusion coefficient were determined under dry cup (performance at low humidity dominated
 by vapour diffusion) and wet cup (performance at high humidity with liquid water and vapour transport) conditions.
 Thermal conductivity increases with rising temperature, moisture content and density. Moreover, a clear
 decrease of thermal conductivity was found with decreasing particle size at the same density level, from
 solid wood over plywood and particle board to fibre board. The water vapour resistance factor of the wood-based
 materials increases with rising density and decreases with increasing moisture content. An influence of
 the particle and fibre board thickness was also revealed. In contrast to the remaining materials, an increase
 of the water vapour resistance factor with increasing moisture content was measured for the coating. The
 diffusion coefficient decreases with rising density and moisture content.

/pdf/thermal-conductivity-and-water-vapour-transmission-1x0se7iurm.pdf

Walter Sonderegger

Papers

Determination of Young’s and shear moduli of common yew and Norway spruce by means of ultrasonic waves

Effects of aging on wood: a literature review

Holzphysik: Physik des Holzes und der Holzwerkstoffe

Thermal conductivity and water vapour transmission properties of wood-based materials

Aging effects on physical and mechanical properties of spruce, fir and oak wood