Experimental evaluation of the fracture toughness on a limestone

Linear Fracture mechanics defines the fracture toughness as an intrinsic material parameter describing the ability of the material to resist to crack propagation. To investigate the effect of the testing method and of the geometry of the samples on fracture toughness determination, a series of tests under different loading conditions was conducted on an oolitic limestone. The tests were performed together with digital image correlation (DIC) analysis and finite elements numerical simulations. The test methods chosen are two types of Brazilian disc tests with a central notch (CCBD and CCNBD), the SCB and ASCB tests. The experimental results show that the obtained values for the mode I fracture toughness K-IC vary between 0.62 and 0.68 MPa.m1/2 which corroborates with the DIC analysis. The mode II/mixed fracture toughness K-IC varies between 0.58 and 0.70 MPa.m1/2 and K-IIC varies between 0.70 and 0.82 MPa.m1/2, for the mixed mode (ASCB, CCBD and CCNBD).