故宫古华轩木构件材料性能劣化机制:化学组分与微观结构的协同作用OA

The mechanical properties of wooden components from ancient buildings are closely related to the dynamic evolution of their chemical components and microstructure.To investigate the deterioration mechanism of material properties,this study took the eave purlin of Guhuaxuan in the Palace Museum as the research object.Multi-scale characterization methods,including Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),and scanning electron microscopy(SEM),were used to analyze the degradation characteristics of cellulose,hemicellulose,and lignin.The correlations between these components and mechanical properties such as density and modulus of elasticity(Ed)were explored,and the gradient deterioration patterns along the eave purlin at different positions relative to the wall(near column,mid-span,and near wall)were analyzed.The results showed that although the eave purlin was free from direct sunlight and generally well-ventilated,its mechanical deterioration still exhibited significant positional differences:the deterioration degree at the mid-span(D)was slightly higher than that at the near-wall end(G),and the near-column end(A)showed the slightest deterioration.Cellulose and hemicellulose degrade significantly at the near-wall end.α-cellulose had the most significant effect on the mechanical properties,with a correlation coefficient of r=0.91(R²=0.83)for Ed,and the decrease in its crystallinity directly led to the deterioration of density and Ed.The local microenvironment was found to be the core factor driving the differential deterioration of wooden components at different positions.This study revealed the interactive actions between chemical component degradation and microstructure evolution during the deterioration of wooden components under conditions free of direct sunlight and with good ventilation,providing a quantitative evaluation framework for the restoration of ancient architectural wood components based on cellulose crystallinity and chemical degradation.