Further understanding of the improved mechanical properties for SiCf/BN/ SiC composites prepared by CVI plus PIP hybrid technique: Application of micro-mechanical methods

In this work, a chemical vapor infiltration (CVI) combined with polymer impregnation and pyrolysis (PIP) technique was used to prepare high-performance SiCf/BN/SiC composites. Compared with the SiCf/BN/SiC composite fabricated by conventional PIP technique, the SiCf/BN/SiC composite fabricated by CVI + PIP hybrid technique showed the significantly improved flexural strength and toughness. The microstructures, macromechanical and micro-mechanical properties were systematically investigated and compared. By applying various micro-mechanical tests (fiber push-in, micropillar compression and micropillar splitting), the in-situ mechanical parameters of different micro-zones for SiCf/BN/SiC composites were obtained accurately. Based on the characterization results of microstructures and micro-mechanical properties, the corresponding toughening process was analyzed in combination of the classical He-Hutchinson criterion. The results indicate that the micromechanical test methods can provide accurate and effective data for the analysis of toughening and fracture process, presenting great potentials in the further understanding of the improvement in mechanical properties of ceramic matrix composites.