Further understanding of the improved mechanical properties for SiC_f/BN/SiC composites prepared by CVI+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 SiC_f/BN/SiC composites. Compared with the SiC_f/BN/SiC composite fabricated by conventional PIP technique, the SiC_f/BN/SiC composite fabricated by CVI + PIP hybrid technique showed the significantly improved flexural strength and toughness. The microstructures, macro-mechanical 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 SiC_f/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 micro-mechanical 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.