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

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.

Thermal conductivity (ThCond), thermal diffusivity and heat capacity of Norway spruce (Picea abies wL.x Karst.) and European beech (Fagus sylvatica L.) have been determined for all principal directions -radial (R), tangential (T) and longitudinal (L) -depending on the moisture content (MC) and ThCond was additionally measured in 158 steps between these directions. The ThCond was determined in a guarded hot plate apparatus. For determining thermal diffusivity and heat capacity, the same apparatus was supplemented with thermocouples and the temperature evolution was evaluated numerically by a partial differential equation. The results show expectedly that ThCond increases with increasing MC, whereby the highest increment was observed in T and the lowest in L direction. ThCond is higher for beech than for spruce in all anatomical directions and the conductivity for both species is more than twice as high in L direction than perpendicular to grain. The highest ThCond is found for beech at a grain angle of approximately 158. The lowest ThCond shows spruce at an angle of approximately 608 between T and R direction. Thermal diffusivity is similar for both species and decreases with increasing MC. Its differences with regard to the anatomical directions correlate with those of the ThCond values. Heat capacity is lower for beech than for spruce and shows a clear increase with increasing MC.

Diffusion processes in samples of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies wL.x Karst.) were determined and quantified by means of neutron imaging (NI). The experiments were carried out at the neutron imaging facility NEUTRA at the Paul Scherrer Institute in Villigen (Switzerland) using a thermal neutron spectrum. NI is a non-destructive and non-invasive testing method with a very high sensitivity for hydrogen and thus water. Within the scope of this study, diffusion processes in the longitudinal direction were ascertained for solid wood samples exposed to a differentiating climate (dry side/wet side). With NI it was possible to determine the local distribution and consequently the total amount of water absorbed by the samples. The calculated values scarcely differ from those ascertained by weighing (F3%). The method yields profiles of the water content over the whole sample, thus allowing the local and temporal resolution of diffusion processes within the sample in the main transport direction (longitudinal). On the basis of these profiles, it was possible to calculate the diffusion coefficients along the fibre direction according to Fick's second law.

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. Wärmeleitfähigkeit und