FRACTURE-BEHAVIOR OF MULTILAYER SILICON NITRIDE BORON NITRIDE CERAMICS/

The fracture behavior of multilayer Si3N4/BN ceramics in bending has b een studied, The materials were prepared by a process of tape casting, coating, laminating, and hot pressing, The Si3N4 layers were separate d by thin, weak BN interlayers, Crack patterns in bending bars were ex amined with a scanning electron microscope. The weak layers deflected cracks in bending and thus prevented catastrophic failure, In one well -aligned multilayer ceramic A, a main crack propagated through the spe cimen although along a zigzag path, A second multilayer ceramic B was made to simulate a wood grain structure, Its failure was dominated by shear cracking along the weak BN layers, Besides crack deflection, int erlock bridging between toothlike layers in the wake of the main crack appeared also to contribute to toughening.