Strain-Dependent Damping of Paulownia Wood at Room Temperature and Constant Moisture Content

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Abstract

"Against the backdrop of global warming and the necessary reduction of CO2, the material wood is experiencing a renaissance as a result of increasing social acceptance. However, questions of harmless reforestation also come to the forefront. Ultimately, plantation cultivation of wood is unavoidable in order to meet the increasing demand for wood in the coming years. Agroforestry is the focus of economic and technical interest in this regard. Paulownia or Kiri tree belongs to the Paulowniaceae family and is the tree with the highest growth rate in the world. It has a large leaf area that can absorb correspondingly high amounts of CO2. Originally from China, it is now planted worldwide and is considered a climate tree. However, it must face the accusation of invasiveness. Therefore, less invasive varieties of Paulownia are of interest. However, these should also have appropriate mechanical properties. One of these material properties is damping, which significantly affects the acoustic behaviour. In this study, the strain-dependent damping was investigated by measuring the logarithmic decrement of free decaying bending oscillations. The measurements were carried out on a common Paulownia species (obtained from plantations in Georgia, Italy and Spain) and a new species of Paulownia obtained from a plantation in Germany. It is worth mentioning that the new wood variety was harvested for the first time in Germany. Since damping is strongly influenced by microstructure, which is in turn influenced by site-specific nutrient supply, this study examined how damping behaviour develops with strain and the extent of its variation. It was found that the damping curves exhibited a strain-independent and a strain-dependent area. The bending modulus was calculated from the oscillation frequency and showed that the values range from about 1024 N/mm2 to 5873 N/mm2 . This large variation appears to stem from the fiber orientation of the tested samples, which also affects the damping values. "

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