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VOLUME 51, ISSUE 3/2010

Qualitative classification of softwood round timber according to European standard EN 1927 Part 2

Language: German
Pages: 5 - 10
Authors: Udo Hans Sauter, Stephan Verhoff

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In the first part of the paper, the main features of the European standard EN 1927, parts 1-3 (2008), concerning quality classification of softwood roundwood has been described. Furthermore, part 1 of the standard, concerning spruce and firs and their

main features was described. The following second part of the paper first describes the special features of pines (EN 1927, part 2). Then, the standard in general will be discussed. One target of the standard, identified by the forest sector and the woodworking industry, is an objective classification of roundwood. The standard on the other hand also considers the quality of timber products produced from roundwood. The chances of classification according EN 1927 and possible implementation problems

are also pointed out in this part of the paper.

Technologies and manufacturing equipment for the forming of solid wood; Part 2: Methods of bending

Language: German
Pages: 11 - 14
Authors: Ulrich Schwarz

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As described, bent wood formerly has been used as structural components in the automotive. This Application has largely been lost. Only the firm Morgan (UK) uses in its sports car a major body of curved mouldings that are made of wood. Surely it can

not be the desire to use wood in magnitude in vehicle. The aim of the research should be to modify the timber in a way that the anisotropy can be used positively.

Long term tests of densified and thermally modified Norway spruce

Language: German
Pages: 15 - 21
Authors: Jörg Wehsener, Peer Haller

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Heat treatments of wood in different ways are well known to improve wood properties, e. g. durability, biological resistance and dimensional stability. The combination of thermo-mechanically densification and oil-heat treatment (OHT) was investigated in the AiF-project NR: 63 ZBG „Thermisch vergütete und verdichtete Fichte für tragende Anwendungen”. The successfully application in laboratory scale reduced the problems of decreasing strength. The up-scaling process was designed to manufacture industrial products. The material was used in a garden and working pavilion as 3-layer solid timber panels and stairs with densified OHT wood. The modified material was tested in bending (DIN 52186, 1978) and dimension stability tests after five years of natural weathering (DIN EN 927-3, 2003). The bending strength of densified and oil-heat treated material was only slightly reduced compared to untreated wood. Samples with

thermal modification and / or densification showed a higher dimensional stability and strength, whereas they are more brittle with the high tendency to split.

Impact of wax impregnation on timber strength

Language: German
Pages: 22 - 27
Authors: Gunthard Scholz, Andreas Krause, Holger Militz

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The influence of different wax types on the strength properties of wood was investigated. Therefore, Scots pine sapwood (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) were impregnated with five different hot melting waxes in a vacuumpressure- treatment. The presence of wax in the wood cavities causes an increased density influencing the mechanical properties. The modulus of rupture (MOR) and elasticity (MOE) for Scots pine was increased significantly by 25 % and 11 %, respectively. The impact bending strength of Scots pine was raised by 31 % compared to the references. The Brinell-hardness for both treated wood species was increased significantly: after wax treatment, beech showed a hardness of up to 126 N/mm2 perpendicular to fibre and 164 N/mm2 parallel to fibre. The ratio between lateral and axial hardness was reduced from more than 1 : 2 to 1 : 1,2 (Scots pine) and 1 : 1,3 (beech), respectively. Among those results, solid wood impregnated with a polyethylene wax revealed significantly higher mechanical properties in comparison

with the other four wax types.

Influence of the MDF characteristics on powder coating and new possibilities of application

Language: German
Pages: 28 - 33
Authors: Klaus Rehm, Bernhard Letsch

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The powder coating technology for MDF and other wood materials is still a compromise between the material properties and the requirements of the application and hardening of the powder. The characteristics of wood materials, in particular the humidity,

the conductivity and the mechanical characteristics have to be adapted to the requirements of the coating. The treatments of the material in the lifetime between the production, the coating and the final use play an important role. The characteristics of the available substrates and their effects on the powder coating quality were examined at the Berner Fachhochschule Biel (BFH). Conclusions were draw for the process chain. A partial break-through could be achieved in the powder coating of several wood materials. The development of new transparent powder coatings with optimized melting and hardening characteristics fosters the powder coating.

Parameters affecting the process safety in the 3-Dcoating of furniture fronts

Language: German
Pages: 34 - 38
Authors: Ingrid Fuchs, Simone Wenk

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Again and again, the furniture industry faces reclamations with regard to foil coated fronts the causes of which are not clear. The examination of those claims showed that bonding between MDF and foil fails particularly in such furniture fronts which are subject to increased stress (heat, humidity).The damage patterns range from foil shrinking to different extend up to the replacement of the foil cover from the entire front. The random occurrence of these types of damage as well as the lack of systematic recording of the failure cases make it difficult to pinpoint there real causes. In addition, there is almost no experience with regard to the long-term behaviour of these fronts. As a result of intensive investigations with the specific variation of selected variables, including a three-month climate assessment, practical insights for improving the bond strength of 3-D laminated MDF components were derived. In addition a measurement device was developed, which objectifies the determination

of the initial and final adhesiveness of the bonding between the support material and décor foil.

Timber-concrete composite road bridges Explanations of the load-bearing behaviour and presentation of a pilot project

Language: German
Pages: 39 - 43
Authors: Karl Rautenstrauch, Antje Simon, Jens Müller

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The load bearing- and deformation behaviour of timber-concrete composite (TCC) road bridges was analyzed explicitly by the Department of timber and masonry engineering of the Bauhaus University Weimar within the scope of a research project funded by the AiF. In this context a suitable connector for bridge building, which transfers the occurring shear forces between concrete and timber, was developed. Calculation methods and principles of construction were elaborated to facilitate the application of timber-concrete composite in bridge building as they have been extant for concrete- and composite steel and concrete bridges for a long time. Based on these results the construction engineer can estimate the parameters of design like bending slenderness of the superstructure, an adequate material selection and constructive boundary conditions quickly and economically. The pilot project demonstrates the innovative idea and the ecological advantages of such hybrid constructions. Therefore it serves as a basis to establish timber-concrete composite road bridges as a modern system solution in the competition at the market.

Breathing mattresses; A quantification method for the air permeability of mattresses

Language: German
Pages: 44 - 48
Authors: Andreas Gelhard

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A research project has succeeded in developing a measurement method and the required test development for the reproducible determination of air permeability of customary mattresses. The characteristics determined on the basis of that allow a clear differentiation of the tested mattresses, both in terms of the air permeability level as well as in terms of the air permeability against the mattress compression. Furthermore, a mathematical model for sufficiently accurate description of the volume flow through a mattress could be established, which describes the dependencies on the initiating differential pressure and the mattress compression and allows generating characterizing parameters. The investigations of possible dependencies of microclimatic characteristics on the air flow properties were added by the aspects of mechanical durability. Mechanical aging effects on the air permeability have been detected. Correlation analysis has demonstrated connections between individual characteristics. A clear correlation between the measured air permeability and single mattress components could not be shown, which points up the complexity of the considered product.

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