Discrete element simulation of SiC ceramic with pre-existing random flaws under uniaxial compression

Because of the outstanding advantages in studying crack propagation and coalescence of brittle solids, the discrete element method (DEM) has been widely used to study the crack propagation in the processing of engineering ceramics. To explore the effects of random defects on the failure mode and mechanical properties of an SiC ceramic material, a DEM model of the SiC ceramic material was established using the Mori–Tanaka method wherein the crack density was determined using the number and length of pre-existing flaws. The established DEM model with the pre-existing random flaws of the SiC ceramic was then subjected to a uniaxial compression test. To eliminate the randomness of the established model as much as possible, more DEM tests were performed with five different randomness flaw distributions. With the increase in the crack density, the compressive strength and crack initiation stress of the material significantly declined. Based on both the fracture specimen and stress–strain curve, the failure mode of the specimen could be divided into two stages: brittle fracture and plastic failure. In the interval with crack densities lower than 0.028, the specimen ruptured along angles in the range of 55–60°, and the failure mode was brittle fracture. Moreover, the effective Young's modulus of the specimen obtained using the DEM was in good agreement with that obtained using the Mori–Tanaka method curve. However, when the crack density was higher than 0.028, which is regarded as a high crack-density interval, the cracks propagated and coalesced in a direction parallel to that of the maximum principal stress. In addition, the failure mode was largely axial splitting. The effective Young's modulus obtained using the DEM was lower than that obtained using the Mori–Tanaka method, wherein only the weak interaction between the cracks was considered.