Determination of Fracture Toughness for Wood

Determination of fracture toughness values in modes I and II for wood are considered. The testing methods are based on the American Society for Testing and Materials standard “plane strain fracture toughness of metallic materials,” which considers mode I only. For the KI test, a modification of the standard is proposed. It is proposed that crack initiation be done with a very thin blade saw, and a larger nonlinearity of the load‐displacement curve is suggested. For the KII test, a similar testing and analysis method is applied to a beam specimen with an end crack. Fracture toughness values are presented, and their dependence on the material and experimental parameters is studied. For mode I., the orientation of the specimen is of great importance. For mode II, the most important variable is the density of the wood material. The fracture toughness value for modes I and II was not affected by the moisture content of the specimens in the range of 10‐20%.