Study On The Relationship Between The Fractal Fracture Characterization Of Wood And Main Mechanical Properties

As fractual crack of wood is very irregular, it is difficult to use traditional testing methods of fracture mechanics to give a quantitative analysis of surface cracks; but fractal theory is a powerful mathematical tool to deal with non-linear,non-equilibrium system. Therefore, this article uses the fractal theory to study the fracture of wood. By the different size of Pinus sylvestris, B.platyphylla to test the sample bending strength, Shun Wen tensile strength, impact toughness macro-mechanical properties and found that the strength of a small sample of wood is higher than the large sample, and the toughness is lower than the big test kind, but the difference is not significant. On samples of the fractal analysis, we find the largest dimension is the tensile fracture surface, followed by the curved surface, the smallest is the impact of fracture; but the fractal dimension is not large differences in between1.05-1.34. Tensile and bending fracture of dimension in small sample is higher than the large sample, but the fracture of dimension in the impact of small sample is lower than the large sample; But the fractal dimension between the same kind of the sample is small differences , about 0.005. From a correlation analysis between the fractal dimension of fracture mechanics and the macroscopic volume,we find that the correlation of Pinus sylvestris is higher than the B.platyphylla. Bending strength, Shun Wen tensile strength and impact toughness are related with the fractal dimension in Pinus sylvestris and B.platyphylla,but the linear correlation is significant differences: the linear relationship is the most significant between impact toughness and the fractal dimension of Pinus sylvestris and B.platyphylla, then the bending strength and its fracture surface fractal dimension but the relationship between the Shun Wen tensile strength and the fractal dimension is not obvious. From the fractal characteristics of fracture, we have established a fracture model of timber fractal. The model calculated from the theory of fractal dimension (1.25) and test the fractal dimension from experiment (1.24) have a better agreement .