Compressive strength of beech and birch at different moisture contents and temperatures
Hajir Al-musawi, Christian Huber, Maximilian Grabner, Bernhard Ungerer, Thomas Krenke, Philipp Matz, Alfred Teischinger, Ulrich Müller
Abstract
Abstract Owing to increased environmental demands to replace petroleum-derived materials with more environmentally friendly materials, research has been directed towards the potential of using wood in the automotive industry. This study extensively investigates the compressive strength ( f c ) of two hardwood species (beech and birch) with different anatomical directions, at various moisture and temperature levels, in an attempt to understand the wood’s behaviour during the forming process. The experimental tests were performed at 20, 100 and 140 °C on specimens with five moisture levels, ranging from completely dry to wet conditions. Overall, irrespective of the investigated direction, the measured compressive strength exhibited a clear exponential trend with increasing moisture content over the whole temperature range. This was capitalised on to present a simple predictive equation to roughly estimate the f c of beech and birch in different moisture and temperature conditions by relating to their dry f c at a reference temperature of 20 °C. The proposed approach was compared with other procedures and trends reported in the literature for the effect of moisture and temperature on the f c of wood. Furthermore, the reduction factors for the effect of temperature on the f c of softwoods, as set out in Eurocode 5 (EN 1995-1-2), were discussed in comparison with the present study findings. It was shown that, although the Eurocode approach is conservative, it may still be applicable for estimating the f c of hardwood species.