VOLUME 0, ISSUE 3/2014

In this study, mechanical properties of wild service trees (Sorbus torminalis L.) at three different locations of Caspian forests (North of Iran) are investigated. The test materials were derived from randomly chosen trees. Mechanical properties such as static bending strength, compression strength parallel to grain, impact strength and shear strength are measured on two levels of moisture content (green and air-dried). The results are obtained for the species at different geographical locations, ages, and mechanical properties. Preparation of specimens and all tests were conducted under the ASTM Standard.

Formaldehyde-free aminoplast resins on the basis of melamine, glyoxylic acid and glyoxal were synthesized and used as an adhesive for various wood-based panels. The results of the exploratory studies reveal promising solutions for the manufacture of particleboards, medium density fibreboards (MDF) and plywood. The formaldehyde emission of the panels is in the range of 0.01 ppm, measured according to DIN EN 717-1 (2005). When using melamine glyoxylic acid/glyoxal resin as a super-plasticizer in cement-bonded particleboards the hydration of the cement in the first hour was considerably accelerated and the mechanical properties of the boards were improved.

Multilayer composite materials are subject to extreme loads during dynamic bending which often lead to failure by delamination. At the Institut für Holztechnologie Dresden gemeinnützige GmbH (IHD) novel composite materials with three-dimensional textile reinforcing elements have been developed and their behaviour against mechanical stresses has been tested. They are particularly useful for the application in sports equipment (snowboards, longboards, ski, kiteboards etc.), but also for applications in the automotive industry. In 3-point bending tests was shown that an increased bending strength in comparison with conventional composite materials is achieved by the integration of the reinforcing elements. The evaluation of the tests was carried out mainly by the method of pairwise comparison. This analysis showed that the number and arrangement of the reinforcing elements have the biggest influence on the bending strength. In contrast the bending modulus of elasticity is closely related to the quality of the lamination of the upper and lower belts.

For the production of a highly porous and flame retardant sound absorber made of wood particles and sodium water glass as binder three methods for foaming and curing the water glass have been developed. The chemical foaming and curing method was not successful. With the chemical foaming and physical hardening only a moderate success could be achieved. The resulting propellant gas does not have the required gas pressure to initiate an open-pored foam structure. However, the samples have a very good homogeneity of the internal structure and have only few structural defects. More often structural defects occurred in the physical foaming and curing processes. Therefore this method led to the possibility of creating an open-cell structure. A combination of physical and chemical foaming resulted in an approximation to the ideal sound absorber for use in acoustic panels.

Due to high axial load-bearing capacity and economical application without pre-drilling, self-tapping screws are widely used in modern timber constructions nowadays. Their withdrawal behaviour, as one mechanism to be verified according to EN 1995-1-1 (2004), is discernibly influenced by the timber member and its moisture content. In case of increase of moisture content above 12 %, test results indicate a significant decrease in withdrawal capacity, which is actually not considered in design procedure. In our paper, we thus concentrate on these experimental studies, carried out in the frame of two research projects. Furthermore, we discuss two models developed for design procedure as well as for data assessment covering a large bandwidth of moisture content and compare them with results from previous investigations.

The project was aiming to generate valid, realistic field data of emissions of active ingredients from wood, treated with copper-amine based wood preservatives. A comparative laboratory test according to CEN/TS 15119-1 (2008) was performed and results of the 19 days of laboratory test were extrapolated for a period of two years. Results of the semi-field test showed copper emissions of 3.8 % and 2.9 % respectively and boron emissions of 23.2 %. The additional hydrophobic timber treatment caused a circa 75 % reduction of the copper leaching. The extrapolation of the laboratory test showed slightly lower copper emissions for the samples treated with impralit-KDS and Korasit KS and slightly higher ones for the samples with the additional hydrophobic timber treatment. The extrapolation of the laboratory test overestimates the boron emissions clearly.

Beside comparing already existing processing, the goal of this research is to develop innovative compressed highly resistant materials from renewable bamboo and formaldehyde-free resin, using Acrodur® more specifically, in order to place growth in rapidly developing countries onto a more sustainable path. China, India, Brazil and lately parts of Africa have rapidly expanding economies with increasing demand for new materials. The production of conventional construction and composite materials such as steel, concrete, or glass fibres in the automotive industry is energy intensive and unsustainable: concrete alone accounts for 5 % of global CO2 emissions. Bamboo is a fast growing, renewable building material widely cultivated in these countries but not utilized to its full potential in modern construction and interior application. Compressed bamboo products (CBP), similar to plywood, oriented strand board, or glue-laminated wood products, therefore have enormous potential to partially replace the use of more energy intensive materials in rapidly developing countries.