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VOLUME 57, ISSUE 2/2016

Influences of the growing area on the visual, physical and mechanical parameters on the example of wood from alpine regions; Part 1: Methods and material, and results of visual grading, annual ring width and knot measurements

Language: German
Pages: 5 - 11
Authors: Roland Maderebner, Michael Flach, Alfred Teischinger, Anton Kraler

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It is often reported, that the growing area of the tree has an influence on the timber quality. But this traditional knowledge is not always confirmed of sawmill owners. With the here presented work the influence of the growing area on the visual, physical and mechanical properties of mountain spruce wood should be detected. Therefore a total of 476 timber beams from two mountain valleys at North- and South Tyrol (Austria and Italy) were sorted by visual and machine strength-grading methods. Afterwards the physical and mechanical properties are determined by bending tests according to ÖNORM EN 408 (2012). The obtained results are compared with results of other investigations about spruce wood from deeper located growing areas. Furthermore it is also taken into account, the influences of the past cultivations at the growing area onto the wood properties. The article is divided into two parts. In part 1, in addition to the chosen methods and materials, also the results of the visual grading, the annual ring width and the knot parameter are presented. In the following part 2, the findings of the experimental studies are clearly represented and discussed in a summary analysis.

Development of pre-treatment methods for wood and wood-based materials by use of a dielectric barrier discharge at atmospheric pressure

Language: German
Pages: 12 - 17
Authors: Richard Wascher, Georg Avramidis, Alexander Neubauer, Viktor Seifert, Holger Militz, Wolfgang Viöl

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This paper presents two processing units that operate on the principle of a dielectric barrier discharge for the pre-treatment of wood and wood materials through plasma. The plasma veneer unit allows pre-treatments of thin continuous substrates such as wood veneers up to a thickness of 4 mm. The plasma conveyor system allows bulk goods, such as wood chips, fibres and granules, to be treated. Both systems proved effective in improving the liquid uptake, while in the case of beech veneers, the conveyor belt system demonstrated greater efficiency at the same injected power. Thermally modified beech veneers showed comparable results in terms of efficacy. The material feed at comparable effectiveness is 60 % higher in the veneer system.

Development of powder coating technologies for indoor and outdoor wooden surfaces

Language: German
Pages: 18 - 22
Authors: Detlef Kleber, Rico Emmler, Simone Wenk, Bernd Brendler

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The introduced enhanced technology allows a successful implementation of powder coating on different wooden surfaces. As a result of systematic investigations, correlations between the electrical properties of the wooden substrates, the performance during the process of powder coating and the end quality of the coated surface have been found. New powder coatings for the outdoor use were applied on solid wood of different wood species and different substrate materials and tested on resistance against weathering on facades, claddings and fences. The results show a good weathering resistance of powder coated surfaces.

Colour analysis of thermally modified and wax impregnated wood after artificial weathering

Language: German
Pages: 23 - 30
Authors: Franziska Baensch, Lothar Clauder, Daniel Cordes, Eckhard Melcher, Alexander Pfriem

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This study focuses on the effects of UV radiation and water spray on different types of modified wood. Therefore, thermally modified samples, wax impregnated samples as well as thermally modified and subsequently wax impregnated samples of beech and scots pine were prepared. During the thermal treatment, the wood was exposed to 180 °C in a nitrogen atmosphere for 1 h. The wax impregnation was performed at approximately 120 °C. Artificial accelerated weathering tests were carried out on each sample type as well as on the unmodified control sample. Twelve artificial accelerated weathering test cycles were run according to EN 927-6 (2006). Gloss and colour measurements were performed before and after the weathering test. After the intensive artificial accelerated weathering, all wood samples revealed increasing lightness L* and decreasing chromaticity C*. For the wax impregnated samples, the most significant loss of gloss G was already observed after the first weathering cycle due to the wax partly washed off.

Review: Wood-based panels for structural applications in mechanical engineering

Language: German
Pages: 31 - 38
Authors: Sven Eichhorn, Andreas Weber, Christoph Müller, Detlef Krug, Katrin Feig

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The use of wood in structural applications in mechanical engineering is known from history. Currently, wood based panels are only used with this feature in niches of mechanical engineering. The paper shows possible causes. Potential application scenarios are presented and the technical decision-makers are described, which determine the use of materials. One solution proposal for enhanced use of wood-based materials in mechanical engineering are mechanically efficient and cost-quality semi-finished products. To evaluate the quality of the semi-finished products, two assessment criteria are presented. The limits of the criteria are defined relative to conventional metallic construction materials. Building on bending tests, two commercial and two especially in a small series produced wood-based panels are evaluated. Finally, application recommendations for mechanical engineers and wood materials manufacturer are given. This should facilitate the application of materials and also help to utilize existing potential.

Review: Wood hardening in the restoration Historical approaches and prospect of possible development

Language: German
Pages: 39 - 46
Authors: Manfried Eisbein

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The wood preservation had already conquered big tasks in the early 19th century. The knowledge of the value of the heritage, helped in developing early preservation techniques. Besides the effort in wood preservation, there were early trials to stabilize worm infested wood. A systematic research was only seen towards the end of the 19th century, early 20th century. A research area for worm infested wood was established in 1902 in Dresden. Research and findings from that time were unfortunately lost over time. In practice one can find a variety of material used. Soaking in glue, hot linseed oil baths, wax-resin mixtures, acetate, nitrocellulose, acrylic resins, epoxy resins, monomers and polymers were some of the approaches used. Despite affirmed success, all approaches remained problematic for the pieces of art, proven by longtime effects. No substance proofed to comply with very high standards in the wood preservation. There has not been any notable success for close to 30 years and restorers are forced to use mainly acrylic resin. It is the goal to develop a substance for wood consolidation, which complies with the wood matrix more accurately. The anisotropy of the wood remains to be problematic. Change in climate and aging lead to new damage. Consolidation after extraction of prior damaging treatment is still only at its beginning.

Review: Performance of bio-based building products; Recent activities within COST Action FP 1303

Language: English
Pages: 47 - 54
Authors: Christian Brischke, Dennis Jones

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COST Action FP 1303 (Performance of bio-based building materials) has been established with the main aim to improve the knowledge on the performance of bio-based materials used as building products and the assessment of factors influencing these, with the aim of increasing their service life. This Action will help in understanding the interlinked relationships between durability, product aesthetics, fibre-moisture relationships, decay hazards and achieving a better understanding of the biology and mechanisms influencing the growth of fungi and other degrading organisms and the consequent damage in terms of discoloration and decay of wood

and bio-based building materials with building design and maintenance. Within this COST Action performance is considered in its manifold meaning, i. e. optical, aesthetical, moisture and functional performance and durability. In this context numerous research activities were initiated. A Europe-wide collaborative field test was started in September 2014 including 28 partners from 15 different European countries observing performance of wood-based material under the effect of the local climate. Two international training schools were held and in total 20 Early Stage Researchers were granted with a short term scientific mission.

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