Real-Time Ultrasonic Investigation of Fiber-Matrix Debonding in Ceramic-Matrix Composite

Abstract

Limitations of ceramic materials such as brittleness, low tensile strength and low fracture toughness are being overcome with the introduction of ceramic matrix composites. The mechanical behavior of these fiber-reinforced composites strongly depends on the fiber-matrix bonding condition. If the bonding is too weak, there is poor stress transfer. On the other hand, for a case of very strong bond, the material behaves in a brittle fashion. Recently, photomicroscopic observations were made and the macroscopic behavior of the material was related to the failure mechanisms and damage development under loading [1]. However, this method is destructive, limited to damage on the surface only and cannot easily detect fiber-matrix debonding. Since fiber-matrix debonding is an important indicator of material response it is important to investigate it nondestructively. An effort was made to correlate macroscopic response with microscopic observations and real-time ultrasonic measurements in a unidirectional silicon carbide/glass ceramic composite under longitudinal tensile loading [2]. In this work, the same material was investigated by ultrasound in an attempt to correlate fiber-matrix debonding with the change in velocity of the polarized shear wave in the plane transverse to fibers. FAILURE