Influence of wood species and natural aging on the mechanics properties and microstructure of wood

As an outstanding representative of traditional Chinese architecture, ancient wooden buildings are a valuable cultural heritage, suffering from natural aging due to long-term sunlight, temperature and humidity, which has caused serious deterioration of the wooden members in many ancient buildings. However, the difficulty of obtaining ancient wood has led to limited research on the microscopic, physical and mechanical properties of ancient wood. In this study, old wood members of five species were obtained from restored buildings, and the moisture content (MC), density, compressive strength parallel to grain (CSPG), conventional static bending strength (BS), modulus of elasticity in static bending (MOE-BS), shear strength parallel to grain (SSPG), compressive strength perpendicular to the grain (CSEG), chemical composition, and microstructure of the new and old woods of each of the five species were studied and compared. In addition, correlations between their densities and various mechanical properties parameters were given. The test results indicated that the physical and mechanical properties of woods subjected to natural aging changed significantly compared to new woods, with extent depending on the wood species, initial properties, storage and conditions, etc. Despite the different wood species, the overall mechanical properties of the new and old woods showed a good positive correlation with the oven-dry density. Natural aging mainly affected the chemical composition of the wood, but basically did not affect the microstructure of the wood.