Dynamic Observation of Fracture Process in a Silicon Carbide- Matrix Laminated Ceramic Composite

Abstract

The dynamic process of crack initiation and propagation in a SiC/BN-Al2O3 laminated composite was observed in situ by scanning electron microscopy. During a bending test with a single-edge notched-beam specimen, an interfacial crack first initiated in the interlayer near the notch tip, after which a through-thickness crack formed in the matrix layer at the notch tip. After the through-thickness crack had grown across the first matrix layer, it was deflected by the next interlayer and again became an interfacial crack. Interfacial cracks and through-thickness cracks were generated alternately until the composite failed. The load-displacement plot of the laminated composite exhibited several peaks, each caused by one propagation of a through-thickness crack. The toughening mechanisms of the laminated composite included crack deflection, interfacial cracking, and through-thickness branch cracking.