VOLUME 48, ISSUE 3/2007

The current issue of wood resources in short supply and the increasing use of wood for energy from biomass are discussed in a contradictory way within the forestry-wood chain. Innovations with respect to resource efficient technologies and product design are not forced hard enough. In several propositions the challenges of the current wood supply situation and the potential of resource efficient technologies are shown.

Although Brosimum guianense is very hardly available for economic utilization, this wood species is internationally well-known due to its distinctive and decorative heartwood. Colloquially known as Snakewood it is listed in the wood anatomical feature description for commercial timbers as well as in sales catalogues of different timber trading companies. The project Pyraa Yae started in Guyana in the year 2003. The aim of this project is to improve the living conditions of a native Makushi village while at the same time conserving its traditions. Among others the project focuses on the inventory of Snakewood trees to establish sustainable utilization of Brosimum guianense based on this information. Furthermore, new applications and markets for Snakewood shall be opened up. Hence a number of investigations on this hardwood species were carried out.

Thermo-mechanical pulping (TMP) leads to the formation of low molecular carbohydrates including monomeric sugars, which mainly originate from hemicelluloses. Preliminary results indicate that hydrothermal degradation of monomeric sugars at a temperature of 100 °C leads to Formation of furfural, formaldehyde and formic acid. Increasing the temperature from 100 °C to 160 °C intensifies the formation of formaldehyde, furfural and formic acid. Moreover, it seems that pentoses have higher susceptibility towards hydrolysis than hexoses.

The determination of wood preservative active substances in the matrix wood is a very complex area. It extends from the statement of a treatment with “old” wood preservatives several decades ago over the determination of wood preservative active substances in the construction unit up to the court-firm proof of an intended treatment with wood preservatives. For each setting of tasks a separate sampling strategy is necessary. In the contribution from the author’s view by material examples possibilities for sampling were pointed out, which should lead with justifiable expenditure to reliable results of analysis. The causes for certain problems are due to the nature of the product wood, its prehistory and the technological parameters during soaking, in connection with the assigned wood preservative prescription. With a competent laboratory at the side the lining up tasks are today and in the future well solvable for an expert for wood preservation.

The elastic constants of solid wood panels were determined using eigenfrequency and bending tests. The determination of the eigenfrequency offers the possibility of non-destructive testing subsequent to the production. MOE determined by static bending tests correspond with values from eigenfrequency by flexural mode. It was hard to determine a direction depending shear modulus out of torsion swinging with the applied method. Thus a “mixed modulus” was determined, which can only be divided into its components by analysing the distribution of strain. The static bending tests generate clearly repeatable results. The method for determining the bending MOE, as presented in DIN EN 789 [12], also works pretty well for smaller samples. Shear modulus have also been measured by using bending loads perpendicular to plane.

The series of papers shows new potentialities for the automation and assurance of efficiency in the machining of shaped wooden parts. These new potentialities are based on the hexapod of simple design. In the first part [1] the relevant spectrum of parts and the Hexapod were initially characterized. In the second part [2] the “Parallel kinematic machining center for shaped wooden parts” was introduced. The efficient connection of the part handling and the machining were demonstrated for the concrete example of a seat shell. In this paper the application-project “machining of large shaped wooden parts” shall be introduced. This project was executed together with the Professorship of Wood- and Fibrous Materials Technology (Prof. Wagenführ) of Technische Universität Dresden. The milling of a node-element “imitation crotch” was selected as a concrete example. The automation technological challenge of this example consisted in the referencing of part for the all around machining, because the part-dimensions were greater than the workspace-dimensions of the machine.

At the professorship of Wood and Fibre Materials Technology of TU Dresden in cooperation with the company Berlebach investigations for the development of a fibre-reinforced astronomy stand were accomplished. Fundamental investigations to the behaviour of load capacity, deformation and vibration behaviour of fibre-reinforced wood composites with small cross-sections have been done. In part 1 of this publication the behaviour of load capacity and the deformation of composites of wood and carbon fibre reinforced plastics are demonstrated.

The dimensional stability depends primarily on the hygroscopic characteristics of the coating materials as well as their internal stress reaction at different climatic loads. In the context of a project promoted by the BMWi comparatively simple relations could be derived, that a widely reliable dimensional stability can be ensured even so with an asymmetrical treatment/coating of the furniture elements. A computable prediction of the deformation of asymmetrically coated components exposed to alternating climatic conditions is possible within the examined measured variable range in principle due to the reached results at the modelling. With the help of statistic analyses significant measured variables could be worked out. The derived relations can be used by manufacturers of furniture fronts for the component construction.