Study on the influence of wood ray morphological characteristics on the tensile strength of wood parallel to grain

The tensile strength of wood parallel to grain is one of the important indicators of wood physical and mechanical properties. Cross-sectional shape possesses a significant effect on the tensile strength parallel to grain, especially for broad-leaved trees with broad wood rays. However the influence of the structural feature of wood rays on the test results, which was commonly ignored. The article focuses on the beech tree with two types of wood rays: broad and narrow, poplar wood with extremely fine wood rays, and dilleniad with extremely rich wood rays. The relationship between the inclination angle and fracture mode of wood rays and the microstructure of wood rays is studied, in order to provide a more accurate scientific basis for determining the tensile strength of wood parallel to grain. The results showed that the inclination angle between the wood ray and the tensile direction has a significant impact on the fracture mode and tensile strength, and the tensile strength parallel to grain without inclination angle is greater than that with inclination angle. Different types of wood rays have a effect on the coefficient of variation of the tensile strength parallel to grain of the specimen. Under the same inclination angle, the Pearson correlation between the wood ray parenchyma ratio and the tensile strength parallel to grain is significantly negative at the 0.01 level (double tailed) or 0.05 level (double tailed). Besides, as the wood ray parenchyma ratio gradually increases, the overall tensile strength of wood parallel to grain shows a downward trend. The fracture surface morphology characteristics of specimens with different fracture modes are different.