Mechanical property and failure mechanism of coated Al₂O_3f/SiO₂ composites by acoustic emission technology (AE)

Al(2)O(3)f/SiO2 composites were fabricated by sol-gel process, with a density of 2.22 g/cm(3), pyro carbon coating prepared via chemical vapor deposition. The interfacial bonding strength between the fiber and matrix was weakened, and the brittle fracture characteristics of the fiber under a high-temperature environment were improved, ensuring the integrity and reliability of the structure. The mechanical property and failure mechanism of the composites were investigated using acoustic emission technology (AE). In the tensile test, microcracks first appeared in the sample matrix, followed by matrix damage, fiber matrix debonding, and partial fiber fracture near the peak load. It was worth noting that many fibers remained undamaged when the load suddenly declined. As the loading continued, these fibers were fully pulled out and consequently loaded until they gradually broke. In the shear test, the load increased to its peak and decreased rapidly, and the proportion of the AE signal generated was extremely small (<=.01). Owing to the brittleness of the matrix under shear force, the crack easily expanded along the interlayer instability such that the sample first showed significant interlayer damage.