Damage mechanism of Al2O3f/Al2O3 composites by acoustic emission technology

Continuous alumina fiber-reinforced alumina matrix composites (Al2O3f/Al2O3 composites) were produced via sol-gel process, the structure, micromorphology, and matrix properties of the composites were characterized, and then the damage mechanism was investigated using acoustic emission (AE) technology. The results showed that the composites were mainly composed of alpha-Al2O3. When the load first increased with time in the tensile test, the composites showed low AE signal energy, and cracks started and expanded in Al2O3 matrix. When the load reached its peak and abruptly declined, the number of AE signal events and accumulated energy increased dramatically. The proportion of AE signal events in the Al2O3f/Al2O3 composites was 0.37, and the proportion of accumulated energy was as high as 0.79, indicating that most of the fibers and the matrix were destroyed at this time. During the short-beam shear test, almost no AE signal was generated when the load rise reached the peak, and the crack instability expanded along the interlayer, resulting in delamination failure. After the initial load decreased, numerous high-energy AE signals were generated with increasing specimen deformation, and many fibers in Al2O3f/Al2O3 composites were crushed synchronously with the matrix.