Characterization of hardness and stiffness of ceramic matrix composites through instrumented indentation test

The determination of the hardness allows useful qualitative conclusions regarding the mechanical properties of materials. It is one of the most economical characterization methods, since this can be carried out with little effort on small specimens. However, due to the heterogeneous structure containing hard and brittle ceramic phases, the determination of hardness of ceramic matrix composites (CMCs) is a challenge and has thus rarely been investigated. In this work, the hardness and the stiffness in out of plane orientation are investigated on Liquid Silicon Infiltrated (LSI) C/C-SiC composites. For hardness tests, a hemispherical indenter is used in order to evaluate residual indentation. The load-unload curve generated during the indentation process is analyzed to determine the hardness and stiffness. The employed experimental procedure is expected to be applicable to other CMCs with similar microstructure.