Characterizing Mode I Fracture Behaviors of Wood Using Compact Tension in Selected System Crack Propagation
Wengang Hu, Yan Liu, Shuang Li
Abstract
The fracture behaviors of four wood species commonly used in wood products were characterized when subjected to compact tension (CT) load in radial-longitudinal (RL) system crack propagation. Meanwhile, the failure modes of evaluated CT samples were compared and analyzed using the fractal dimension method. The results showed that wood species had a significant effect on fracture characteristic values, including maximum fracture load, critical stress intensity factor and fracture energy. These characteristic values changed in the same way, i.e., beech wood CT samples obtained the maximum characteristic values, followed by ash, okoume, and poplar in descending order. The fracture behaviors of all wood species evaluated can be described by combining linear and exponential fitting equations at the crack initial stage and evolution stage, respectively. Linear positive proportional relationships were observed between fracture characteristic values and fractal dimensions calculated using cracks in front and left views of CT samples. However, the relationships between fracture characteristic values and fractal dimensions calculated using fracture surfaces were negative. The fractal dimensions of cracks in front view of CT samples could be a better indicator used to predict critical stress intensity factor and fracture energy, which had greater correlation coefficients beyond 0.95.