STATE-OF-THE-ART of WOOD FRACTURE TOUGHNESS ALONG THE GRAIN

Defects may lead to wood fracture under low stress state. In this paper we summarize the state-ofthe-art of wood fracture toughness along the grain, which is an important mechanical parameter of wood. We introduce main fracture toughness test methods, and analyze the advantages and disadvantages of different test methods and data processing methods. We focus on the related influence factors of the fracture toughness, such as wood species, density, moisture content, wood fiber bridging effect, specimen span/depth ratio, and so on. Moreover, we summarize the research results of the fracture toughness's size effect. Considering the wide usage of engineered wood products in practice, the research sate of wood adhesive bonds fracture is also introduced.