A Comparative Study on the Temperature Effect of Solid Birch Wood and Solid Beech Wood under Impact Loading.

In order to use wood for structural and load-bearing purposes in mechanical engineering, basic information on the impact behaviour of the material over a wide temperature range is needed. Diffuse porous hardwoods such as solid birch wood (Betula pendula) and solid beech wood (Fagus sylvatica) are particularly suited for the production of engineered wood products (EWPs) such as laminated veneer lumber (LVL) or plywood due to their processability in a veneer peeling process. In the frame of this study, solid birch wood and solid beech wood samples (300 × 20 × 20 mm3) were characterised by means of an impact pendulum test setup (working capacity of 150 J) at five temperature levels, ranging from -30 °C to +90 °C. The pendulum hammer (mass = 15 kg) was equipped with an acceleration sensor in order to obtain the acceleration pulse and deceleration force besides the impact bending energy. In both solid birch wood and solid beech wood, the deceleration forces were highest at temperatures at and below zero. While the average impact bending energy for solid birch wood remained almost constant over the whole considered temperature range, it was far less stable and prone to higher scattering for solid beech wood.

Temperature-Related Properties of Solid Birch Wood under Quasi-Static and Dynamic Bending.

The project WoodC.A.R. investigates the capabilities of wood and engineered wood-products (EWPs) for their application as a load-bearing material in automotive applications. For crash-relevant components, materials have to provide a high impact bending energy over a wide range of climatic conditions. This study investigates the effect of temperature on the bending behavior of solid birch wood beams (800 × 90 × 43 mm3) under quasi-static and dynamic loading. Specimens were exposed to a three-point bending test with lateral confinement, replicating the hypothetical installation environment in a car, at five temperature levels: -30 °C, 0 °C, +30 °C, +60 °C, and +90 °C. A cylindrical impactor (D = 254 mm, m = 91 kg) was propelled against the center of the beam with an initial velocity of 8.89 m/s (dynamic) and at a constant velocity of 10 mm/min (quasi-static), respectively. Specimens were conditioned in a freezer and a climate chamber, respectively. Temperature was monitored prior and during testing. Bulk density and global fiber deviation were determined afterwards. In both, the dynamic and the quasi-static load case maximum force slightly decreased with increasing temperature, but remained almost constant at temperatures exceeding +30 °C. On average, the maximum dynamic peak force level was twice as high as in quasi-static tests. In the quasi-static tests, the energy absorption remained constant at elevated temperatures (+30 °C to +90 °C) but decreased by about 50% at lower temperatures -30 °C and 0 °C. In the dynamic tests, the energy absorption remained almost constant throughout the entire temperature range.