VOLUME 48, ISSUE 5/2007

In various archaeological excavations smaller wooden samples were found, which do not include the necessary number of 50 tree-rings. Typically only one parameter (total ring width) is used. Particularly with shorter series, incorrectly dated positions can have a higher correlation than correctly dated positions. By measuring more than the tree-ring width parameter we hypothesize that we can improve the cross dating by effectively increasing the sample size or the degrees of freedom in case of spruce (Picea abies [L.] Karst.). Dendrochronological dating of softwoods is possible by using univariate and multivariate methods. On the one hand, the acceptance of wrong correlations may happen on the basis of only one tree-ring feature. On the other hand, the multivariate cross-correlation leads to a higher value of efficiency during the dating of spruce samples by a more detailed characterisation of the xylem structure by X-raydensitometry and using of more tree-ring features with the described procedure

The PrimWood Method is a new production concept for manufacturing of high quality boards, components and panels from softwoods and hardwoods. The method generates knot-free boards, components and panels with vertical annual rings. The PrimWood Method increases the quality of the wood, compared to wood processed with traditional methods (harder surface, increased shape stability, freedom from cracks, easier and faster processing, less waste and a more even finishing). The wood is also given new aesthetical characteristics (e. g. even texture, knot-free surfaces and decorative finger-joints). The PrimWood Method also improves the raw material utilization, with resulting positive environmental effects, since a renewable resource is utilized more efficiently.

The use of wood as a structural or cladding material in multi-storey buildings is limited due to an uncertainty of architects, clients and insurance companies. In the focus is – apart from the alleged reduced durability – the fire safety of the buildings. This paper gives an overview about the different possibilities to influence the performance of wood and wood based materials under fire impact positively.

The thermal conductivity of three-layered solid wood panels from Norway spruce (Picea abies [L.] Karst.) and of various wood-based materials (fibre boards and plywood) was tested with regard to temperature and moisture content and by the three-layered solid wood panels additionally with regard to growth ring position and variation of the middle layer (middle layers with holes, middle layers from other woodbased materials). The thermal conductivity increases with increasing temperature and moisture content. In the radial direction, the thermal conductivity of spruce wood is 8 % to 10 % higher than in the tangential direction. Holes in the middle layer of three-layered panels reduce the thermal conductivity. The use of wood-based materials in the middle layer of three-layered panels slightly increase the thermal conductivity by use of high-density materials and highly decrease the thermal conductivity by use of light materials.

Computer controlled machining equipment and centres that provide accuracy in the thousandth millimetres range, represent the pinnacle of woodworking technology. When cutting happens and, as a consequence, forces act in several different directions. For micrometer precision control of the cutting tool, work pieces have to be fastened securely, deprived from their degrees of freedom, to achieve maximum quality. The most frequent clamping method for pieces with planar surfaces today is fastening by a vacuum field. The vacuum-induced hold-down force, together with l0 and l (static and kinetic friction coefficients, respectively) creates the friction force that prevents the work piece from shifting. The purpose of numerous measurements was the analysis of the work piece movement. The shifting of the material upon intensive cutting or at the start of the cutting process is a frequent problem. In this article with two parts the friction coefficients when clamping work pieces of different wood species resp. wood materials by vacuum under different conditions are to be investigated.

At the Institute of Wood and Paper 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 and 2 of this publication (holztechnologie issue 3 and 4/2007) the behaviour of load capacity and the deformation of composites of wood and different synthetically fibres or rather adhesives and reinforcing degree are demonstrated. The following part 3 is dedicated to the reinforcement of wood with different manufacture variants for composites.

Ultrasonic edge banding was tested for the manufacture of edge banding for furniture under moisture conditions. This technology used high-power ultrasonics for melting a separately fed glue stripe (PUR-stripe). Traditionally heated gluing devices with gluing roll were not necessary. Time cost for cleaning and service were cancelled. High-quality edge bandings by ultrasonics had been possible for a wide range of edge materials and work piece thicknesses. Testing of edge banding quality was performed by measuring the adhesive strength according to EN ISO 4624. Additionally a visual control of the banding surface was done.

In 1977 the German company Bison-Werke, Springe, applied for a patent to combine wood particles with thermoplastic resins to press boards. The boards typically consisted of 60 % wood particles and 40 % of a thermoplastic resin, e. g. polypropylene. Both components were scattered in powder form to a cake which was pressed to boards. After re-heating the boards could be compression moulded to three dimensional parts. This invention shows that composites of wood and thermoplastics, wood-plastic composites (WPC) are not an American invention from the beginning of 1990er years. But if WPC are made by extrusion technology the USA should to be seen as inventor.

The antimicrobial and colouring properties of extracts from algae and mosses were investigated at a research project finished at the Institut für Holztechnologie Dresden (IHD) recently. The possibilities for an application as environmentally friendly preservatives for wood and coatings were estimated. Extracts produced by the Institut für Getreideverarbeitung Nuthetal (IGV) were tested at the IHD, at first on agar and than in combination with different materials. It was found that the extracts from a brown algae species and from a moss species possess an antimicrobial potential especially. But, an application in paints and construction materials respectively could be possibly in future only, if further specific research is carried out and the active ingredients are identified and concentrated.