Effects of residual stresses on the fracture properties of non-oxide laminated composites

A layered ceramic composite in the AlN-SiC-MoSi2 system was prepared with the outer layers under residual compressive stress. The mechanical properties of the constituent layers and of the laminated composite were measured. Due to the residual compressive stress, the fracture strength of the laminated composite was higher than the strength of the outer layer material. The fracture toughness of the laminar composite was evaluated by SEVNB. The resulting values were compared with a fracture mechanics model and a good agreement was found between the experimental measurements and the calculated apparent fracture toughness profile.