Data of tensile rock, mode II and mode I fracture toughness

The empirical relationships between tensile strength, mode I and mode II fracture toughness obtained by previous studies have the problem of a small amount of data for fitting, and more data are needed for further study. There is a discrepancy between the theoretical prediction and the experimental results of the relationship between mode II and mode I fracture toughness. Because of this, a review is conducted to determine the relationships among tensile strength, mode I fracture toughness, and mode II fracture toughness from the data gathered from the available literature. The results indicate that the mode I and mode II fracture toughness have linear relationships with tensile strength with the linear coefficient of 0.141 and 0.219, respectively. The linear coefficient between mode II and mode I fracture toughness is 2.389, indicating that the classical mixed mode criteria are mistaken the empirical relationship between mode II and mode I fracture toughness.