The mechanical fracture characterization of non-linear flexible ceramics using digital image correlation

During their application, refractory materials are submitted to several thermal shock attacks. That is why; improving their thermal shock resistance has a great importance and can enhance their lifetime. This characteristic is directly related to strains to rupture. The non-linear mechanical behavior which characterizes specific developed ceramics, and is a consequence of their micro-cracked microstructure, leads to the increase of their strain to rupture level. This limit allows a better resistance to thermal shock solicitations. Magnesia spinel materials are good candidates to characterize such non-linear mechanical behavior dependent on their microstructure. This non linearity is due to the presence of micro-cracks network. Indeed, mechanical behavior can vary from a fragile one to a large non-linear one according to the degree of micro-cracking present within the material. In this paper, to investigate the crack propagation and the non-linear mechanical behavior of this material, wedge splitting test was used and coupled to digital image correlation technique. Results underline the influence of the addition of spinel on the non-linear mechanical behavior by comparing the non-linear mechanical behavior of magnesia spinel with pure magnesia. Besides, results clarified also the crack propagation mechanisms which are specific to these heterogeneous materials.