Thermal expansion mismatch inter-inclusion cracking in ceramic systems

Abstract De-cohesions or radial cracks are commonly observed in ceramic composites submitted to temperature variation, mostly associated to the thermomechanical property mismatch among the material constituents. However, the presence of cracks in the middle region between two inclusions was not satisfactorily explained in the literature. This sort of crack is mainly detected for high-volume fraction of inclusions, although it can be also found in low-volume ones. This communication aims to study the origin of this inter-inclusion cracking via computer simulation using the finite element method (FEM) and the minimum energy theory. It is known that due to the randomness of inclusions' location in ceramic composites, their distance is variable and statistically tend to be smaller for high-volume fractions. FEM simulations pointed out that for low volume fractions the energy distribution between inclusions presents an “U” profile, where the matrix-inclusion interface is the most stressed region. For high volume ones it is the opposite, the most stressed region is the midpoint between the inclusions. Based on that, the closeness of the inclusions would be the main cause of inter-inclusion cracks, as a result of a change in the energetically most stressed region, from the matrix/inclusion interface to the equidistant location between two inclusions.