Observation and Modeling of Brittle Fracture Initiation in a Micro-Heterogeneous Material

Observations and characterization of brittle fracture initiation in a micro-heterogeneous material (sandstone) are conducted using the standard indirect tensile strength test. Acoustic emissions, optical microscopy and scanning electron microscopy (SEM) are employed for monitoring and characterizing the discrete micro-mechanical events preceding macroscopical fracture. The observations suggest that brittle fracture initiation is the end result of a microscopic damage accumulation process. A simple statistical model of micro damage accumulation leading to brittle fracture in a micro-heterogeneous material is also proposed. The model is calibrated by matching the coefficient of variation of measured ultimate stress with that resulting from the proposed model.