VOLUME 63, ISSUE 4/2022

The challenge of the climate crisis requires novel bio-based and CO2 binding, as well as functionalized high-performance materials that go beyond the state of the art. Wood as a renewable raw material offers the basis for such materials, but due to its naturalness also material-technical challenges prevail that need to be overcome. In the course of a strategic project, three main topics were specifically addressed with new methods that play a key role in the development of bio-based materials. As a result, fundamental steps in the UV and water protection of wood surfaces were achieved, which will significantly influence the further development of natural wood surface treatments. By specifically reducing the density of bark through delignification processes or by combining it with newly formulated bio-based matrix materials, it was possible to create highly porous material structures with outstanding insulating properties. In the area of sustainable and bio-based bonding of wood-based materials, the targeted modification and cross-linking of plant proteins enabled the formulation of binders that are not only bio-based but also have increased wet strength. The project has enabled fundamental steps to be taken towards sustainable and biobased wood-based materials, which will form the basis for future material developments to substitute fossil-based materials.

In order to ensure durable bonding of glued laminated timber, the process steps defined in accordance with EN 14080 (2013) for production must be strictly adhered to in conjunction with the prescribed monitoring requirements. The defined boundary conditions are largely based on experience and are essentially oriented to the existing shear strengths of the wood. Within the scope of this work, the adhesive joint stresses occurring as a result of the manufacturing process (pressing and manipulation) are investigated numerically. In particular, the influences of the position of the pith in the board cross-section are in focus.

The investigations relate to the delignification and acetylation of beech wood veneer and the combination thereof. Furthermore, the effects of a treatment combination are tested and the resulting material properties are determined. With removal of lignin (reduction to 0.3 %) by degradation of the middle lamella and the formation of intercellular cavities an increasing hygroscopy in the area of chemisorption and decreased water contact angle (31°) could be measured. When acetylating untreated wood with acetic anhy-dride, the equilibrium moisture content was reduced by approximately 62 % at a weight percent gain of 16 %. Acetylation after lignin removal (WPG 15,5 %) causes hydrophobic properties with increased porosity. The water contact angle was increased to 71° and the water sorption dimin-ished. Thus, swelling was decreased.

Wooden decking is an important product group, situated in the area of conflict between high user demands and heavy use. They were the subject of the European research project “Quality and Assessment Programme for Exterior Wood Coverings – EURODECK”. The two-year project within the framework of the EU CORNET programme was carried out jointly by the Institut für Holztechnologie Dresden (IHD) and Holzforschung Austria (HFA) from 2020 to 2022. Funding for the IHD sub-project was provided by the German Federal Ministry for Economic Affairs and Climate Protection (BMWK) via the Arbeitsgemeinschaft industrieller Forschungsvereinigungen “Otto von Guericke” e. V. (AiF) (German Federation of Industrial Research Associations). In the project, quality criteria and require-ments as well as testing and evaluation methods for outdoor coverings were analysed, taking into account relevant standards and regulations, various experimental investigations were carried out and a user guide was developed. These guidelines can be used to plan timber coverings in such a way that a high level of serviceability and service life can be ensured. This article presents the guidelines and selected results.

The collection and removal of wood dust and chips are technically challenging and of great economic importance to companies in woodworking and wood-processing industries. Numerical flow and particle simulations help to analyse chip collection systems and optimize their design. For modelling, knowledge of particle sizes and shapes is required. In particular, particle shape affects the behaviour of granular media in many ways. However, it is not possible to represent a large variety of shapes and sizes of wood chips using these models. Therefore, an approach is required to analyse chip mixtures and transform them into surrogate mixtures suitable for simulation. This study demonstrates the use of dynamic image analysis and a classification algorithm for the creation of suitable surrogate mix-tures. The analysis and classification of particle features are explained after presenting the influence of the chip shape on chip flight and chip collisions. Finally, the results are presented and summarized.