Mechanical and Fracture Behaviors of Brittle Material with a Circular Inclusion: Insight from Infilling Composition

The inclusion plays a crucial role in mastering mechanical responses and cracking behaviors of brittle materials. In this work, a series of uniaxial compression tests were performed to investigate the effect of infilling composition (i.e., proportion and grain size) on the mechanical responses of brittle materials. Digital image correlation (DIC) and acoustic emission (AE) techniques were applied, respectively, to measure the surface strain and internal AE signals of brittle materials for further analysis of failure behaviors. The results demonstrate that both infilling proportion and grain size significantly influence the cracking processes and failure modes of brittle materials. The uniaxial compressive strength (UCS) and deformation modulus increase with the increase of the cement proportion or infilling grain size due to the stress redistribution around the inclusions. The debonding behavior between inclusion and matrix becomes significant when the specimens have a higher cement proportion or larger grain sizes. Interestingly, the number of accumulative and peak AE events is negatively correlated to the cement proportion and grain size. Three failure modes (tensile failure, shear failure, and mixed failure) are observed, and the mixed failure mode is the dominant one. Using a bonded-particle model (BPM), the numerical results can verify the experimental observation regarding debonding and cracking behaviors based on the full-field stresses and fragment characteristics analysis, and further reveal the failure mechanism of the specimen with infilling with different infilling compositions. Based on elasticity and complex variable theory, the derived dimensionless stresses around the inclusion interface can well explain the debonding behavior with rigid and soft inclusions, which is in reasonable agreement with numerical results. The current study could provide technical grantees for the safety and reliability of practical engineerings such as slope engineering, back-filling in mining, and tunnelling engineering.