Fracture tests were performed on sandstone specimens under three-point bending with a variety of notch positions to achieve KII/. KI= 0-12%. At peak load, the maximum crack opening displacement measured by digital image correlation was 45. μm under mixed mode loading and 30. μm under mode I, and these values were used to determine the length of the cohesive zone: 10-12. mm for mixed mode and 5-7. mm for mode I. For mixed mode fracture, the displacement in the cohesive zone was identified to be opening only, while sliding and opening were detected along the remaining length.
Bibliographical noteFunding Information:
The authors sincerely thank the financial support from NSF grant CMMI-0825454, the MSES/Miles Kersten Chair, the National Natural Science Foundation of China (Grant No. 51304225), and the Science Foundation of China University of Petroleum, Beijing (No. 2462013YJRC036).
- Cohesive zone
- Digital image correlation (DIC)
- Fracture initiation and propagation
- Mixed mode fracture
- Quasi-brittle material