VOLUME 63, ISSUE 1/2022

The article describes the goals, necessity and project structure of the project “Wood in mechanical engineering (HoMaba)”. It is the starting point for the following contributions, which describe selected results of the project.

round robin test was conducted to compare the influence of different measuring systems on the modulus of elasticity, tensile strength and Poisson's ratio. A tensile test was carried out on high-density fibreboard made of pine wood using eight setups, which varied in extensometer type, clamping jaws, and upper limit of the load sensor. Not all extensometers were suitable for measuring Poisson's ratio and an increase in tensile strength with increasing sensitivity of the force sensor was observed. The influence of the setup was greatest on the modulus of elasticity. This result is relevant for all applications in which precise material parameters are required, such as the simulation of components under load.

This publication presents an implementation and evaluation method for tensile tests at veneers. Results are exemplarily presented and discussed by birch veneer. Mechanical parameters such as presented in this publication are necessary for the dimensioning and evaluation of veneer-based products. By means of such veneer parameters, a prediction of the mechanical properties, e. g. the stiffness of veneer-based products, is possible which allow calculations and simulations.

This publication addresses the question of whether adhesive-coated veneers are more suitable than native veneers in order to obtain characteristic values for the calculation and simulation of plywoods. The question was investigated by means of experimental tests, analytical calculation and simulation and the results were discussed based on beech veneer, partly coated with phenol-resorcinol-formaldehyde adhesives. The results show that coated veneers offer better agreement with calculation approaches and simulations of plywoods than native veneers and are also superior to a simplified approach of a laminate as veneers with separate adhesive layers.

To plan components for the use in mechanical engineering, simulations of the material are necessary. The properties of these materials are gained by testing. Testing methods of solid wood are standardized only for a longitudinal loading. The material testing which is the base for realistic

simulation of components needs to be standardized to secure the comparability of different materials. The geometry of the specimens is an important part of the testing methods. The forms have to be evaluated not only regarding the fitness and manufacturing but also enable the usage of innovative three-dimensional optical measuring systems. Therefore, different forms of tensile rods are compared to define suitable geometries for tensile test in direction of as well as perpendicular to the fibre.

For the calculation and dimensioning of wooden constructions the knowledge of mechanical parameters is necessary. These mechanical parameters include among others the shear modulus and the shear strength. The publication presents these determined parameters for veneers and solid wood. Veneers are the basic material of layered wood, thus differences between these parameters for veneers and solid wood are discussed and evaluated. As a result of the investigations, the parameters of veneer and solid wood are compared and an assessment is made as to whether it is permissible to apply these solid wood parameters to veneer as well.

In this article, calculation and simulation concepts for wood-based materials for use in mechanical engineering were presented and validated using laboratory tests. For the calculation concept, a good match between the calculated and experimentally determined curves could be established. In contrast, it was shown that the calculation of the proportionality limit requires further analysis. The simulation concept presented also showed good agreement with the experimentally determined component curves.