Microcracks with unexpected characteristics induced by CTE mismatch in two-phase model materials

In order to study model microstructures representative of industrial refractory materials, this work is devoted to the elaboration and microstructural characterisation of two-phase model materials able to develop interfacial damage by thermal expansion mismatch between the matrix and inclusions. The studied materials are composed of a vitreous matrix surrounding dense alumina balls (Al2O3 99.9%). As expected, because of the not null dilatometric dissension (Da < 0 with amatrix < ainclusions), all the samples exhibit partial decohesions at the matrixinclusions interfaces. But one also observes the presence of two types of unexpected cracks: straight cracks in the median plane between two inclusions and circular cracks around inclusions. Numerical, analytical and experimental tools were used to study the origin of such unexpected defects.