Acoustic emission characterization of fracture toughness for fiber reinforced ceramic matrix composites

The fracture toughness of a carbon fiber reinforced silicon carbide composite was investigated relating to classical critical stress intensity factor K_IC, work of fracture, and acoustic emission energy. The K_IC was obtained by the single edge notch beam method and the work of fracture was calculated using the featured area under the load-displacement curves. The K_IC, work of fracture, and acoustic emission energy were compared for the composites before and after heat treatment and then analyzed associated with toughening microstructures of fiber pullout. It indicates that the work of fracture and acoustic emission energy can be more suitable to reflect the toughness rather than the traditional K_IC, which has certain limitation for the fracture toughness characterization of the crack tolerant fiber ceramic composites.