Variability of mechanical properties of hardwood branches according to their position and inclination in the tree
Tobias Nenning, Andreas Tockner, Johannes Konnerth, Wolfgang Gindl‐Altmutter, Michael Grabner, Christian Hansmann, Simon Lux, Maximilian Pramreiter
Abstract
Although hardwood building materials are mainly produced from the tree stem, the branches of deciduous trees make up a significant proportion (20–50%) of their above-ground biomass. Regrettably, the mechanical properties of branches are largely unknown and they are mainly used as fuel, overlooking their potential as valuable construction materials. Therefore, we conducted quasi-static tests on branch and stem wood from beech, oak, and poplar trees, evaluating wood density, tensile, compression and bending strength, and elastic properties. The mechanical properties were correlated with precise positional data from 3D point clouds of the sample trees. Our findings revealed significant differences between branch and stem wood, most notably in density and tensile strength. The linear regression models revealed that bending strength depends primarily on density and branch slope, and secondarily on branch top side and diameter. Applying laser scanning technology can help to better understand the variability and predict the performance of branch wood, enabling more resource- and carbon-efficient processing into building materials.