Tensile properties and failure mechanism of the SiCf/SiC minicomposite with multi-layered (BN/SiC)n interfacial coatings at room temperature

Abstract

To overcome the brittle fracture of ceramic matrix composites, the interfacial coatings between continuous fibers and the ceramic matrix, especially boron nitride (BN) and silicon carbide (SiC) coatings were often introduced into the composites to improve the interface properties. This work focused on the use of chemical vapor infiltration (CVI) and precursor infiltration and pyrolysis (PIP) to fabricated SiC fiber-reinforced SiC (SiCf/SiC) minicomposites with interfacial coatings. Single BN, double-layered BN/SiC, and multi-layered (BN/SiC)2 interfacial coatings were deposited on SiC fibers from BCl3-NH3-H2 and MTS (Methyltrichlorosilane)-H2 systems in a low pressure hot-wall CVI reactor. Room-temperature tensile testing was used to evaluate the influence of different interfacial coatings on the tensile properties and failure mechanism of SiCf/SiC minicomposites. The minicomposites with (BN/SiC)2 coatings performed the highest fracture strength of 630.9 MPa. The mechanical behaviour of the composites was characterized by the universal testing machine with an acoustic emission (AE) detector, a scanning electron microscope (SEM), and an energy dispersive X-ray spectrometer (EDS). The existence of (BN/SiC)2 coatings provoked the interface debonding in the minicomposite both at the BN/fiber interface and the interface between BN and SiC layers, prolonging the crack propagation paths and noticeably improving the fracture properties of the minicomposite.