Mode I fracture toughness estimation of wood by DCB test

The mode I fracture toughness of wood obtained by the double cantilever beam (DCB) test was analyzed by six conventional analysis methods: two methods based on elementary beam theory, Williams’s correction method, modified beam theory method, and two compliance calibration methods. In addition to these methods, the compliance combination method, which was originally proposed by the author for obtaining the mode II fracture toughness by the end notched flexure (ENF) test, was applied to the DCB test. In the compliance combination method, the strain at a certain point of the cracked portion of the specimen was measured, as was the loading-line displacement and critical load for crack propagation. Similarly to the mode II fracture toughness analysis for wood by the ENF test, the compliance combination method is more advantageous in practice than the other ones examined here in that the fracture toughness can be determined by the DCB fracture test alone without requiring separate tests, which should be conducted in the modified beam theory and compliance calibration methods.