VOLUME 55, ISSUE 1/2014

In this research, wet depitting bagasse fibres (Saccharum spp.) were used for producing medium density fibreboard (MDF). The influence of steaming time (5 min, 10 min and 15 min) and steaming temperature (170 °C and 180 °C) on MDF properties were investigated. The results showed that with increasing of the steaming temperature and steaming time, bending properties of boards were decreased. The maximum modulus of rupture (MOR) and modulus of elasticity (MOE) properties were observed at five minutes steaming time, the minimum properties at 15 minutes. With increasing the steaming temperature, internal bond (IB) decreased. The effect of steaming time on internal bond is not statistically significant. The results derived from investigating the steaming temperature on thickness swelling (TS) after two hours and 24 hours of immersion in water showed that increasing steaming temperature has improved thickness swelling. The optimal steaming temperature for producing MDF from bagasse fibres was 170 °C within five minutes steaming time.

For using bamboo as a construction material, the behaviour under static and cyclic load is of interest. Whereas studies on cyclic loading cases of bamboo do not exist, in the present study fatigue tests were performed on the bamboo species Phyllostachys pubescens and Guadua angustifolia. Material and methods were described in part 1 of this publication. It was found that in the zones of the internodes the fatigue strength under cyclic loading for Phyllostachys pubescens is 49 % and for Guadua angustifolia is 52 % of the quasi-static tensile strength.

The changes of the mechanical properties of tonewood, consisting of thin sheets of spruce and maple over a period of up to three years have been investigated. It turned out that the elastic modulus increases by 1-2% per year whereas the wood thickness decreases. Moreover a remarkable increase of the internal damping occurs which amounts to about 10% per year. Even samples cut from 600 years old wood from the frame work of a roof show significant changes of mechanical properties.

The Barkhausen noise method for evaluation of residual stresses distribution map in the circular saw blade was used. Natural frequencies and vibration modes were also measured aiming at comparative assessment of the saw blade quality. The tangential resolution of 10° seems to be not sufficient for precise assignment of fluctuations of the Barkhausen noises with deformations of the diameter vibration mode arms. Measurements performed indicated moderate good quality of the saw blade.

The improvement of product quality and production efficiency is increasingly sought in modern manufacturing processes. However, increasing cutting speed can lead to dangerous process situations in respect to operator safety and machine damage. These situations generally arise due to inappropriately clamped or imbalanced tools at high rotational speed. With the aim of improving safety in machining processes, this paper presents current investigations to develop a sensor-integrated machining spindle for planing machines. In order to achieve this goal, the Institute of Machine Tools and Production Technology (IWF), in cooperation with the Fraunhofer Institute for Surface Engineering and Thin Films (FhG IST), are investigating the application of a novel thin film sensor system. The sensor system is primarily based on the piezo-resistive hydrocarbon coating Dia- Force®, the electrical resistance of which definably changes under mechanical load. With a thickness of 7 μm it can be directly applied into a mechanical joining system in order to measure the clamping force and imbalanced tools. An additional strain gauge for measuring the cutting force completes the machine and process monitoring system.

Wood decay fungi cause extensive damage on load-bearing constructions of buildings. Traditional identification methods of wood decay fungi using macroscopic and microscopic analysis of morphological features might be time-consuming and misleading. Most molecular DNA methods, such as PCR (Polymerase Chain Reaction) are using fungus-specific primers or probes and direct sequencing. The ITS (Internal Transcribed Spacer)-rDNA (ribosomal Deoxyribonucleic Acid) is an accepted genetic marker and the most widely sequenced DNA region for identification of indoor wood decay fungi. The sequencing and the sequence data analysis of the entire ITS-rDNA region of 27 indoor wood decay basidiomycetes (121 fungi samples) for development of DNA microarray diagnostics are described below.

Flat wooden roofs are becoming more and more popular. There are many built examples; however, among them are some cases of damage. Especially non-ventilated constructions are relatively sensitive, thus moisture-caused damages may appear. However, in case of compliance with certain boundary conditions, these constructions show no moisture-related problems. This has been demonstrated recently by two large research projects, firstly at MFPA Leipzig, secondly at Holzforschung Austria, Vienna. The updated version of DIN 68800-2 (2012) specifies constructions without additional verification, such as non-ventilated, non-covered and non-shadowed roofs with moisture-variable vapour check – thus wooden building parts can be classified for use in class 0 (no chemical wood preservation necessary) by direct compliance with DIN 68800-2 (2012). More sophisticated constructions, such as with green roof or terrace, must and can be verified by hygrothermal simulations (WUFI, Delphin). The fixed boundary conditions lead to a very high level of safety.

Small and medium-sized enterprises are challenged by fulfilling market demands for environmentally benign products, proven by transparent and reliable evaluation such as assessments based on a life cycle approach. In the assessment two types of wood are compared: bilinga and pressure impregnated pine. Functional unit is 1 m² covered terrace. Data sources are industry and the database ecoinvent (including transports). The impact assessment is done with CML 2001. The impact categories assessed are global-warming potential (GWP), acidification potential (AP), ozone depletion potential (ODP), photochemical ozone creation potential (POCP), and eutrophication potential (EP). Inventory shown is cumulated energy demand (CED). Results show that in all impact categories the terrace made of pine is the one most environmentally benign, environmentally disadvantageous is tropical wood bilinga, in-between are the deckings made of WPC.