Effect of geometrical factors on the mechanical properties of Si3N4/BN multilayer ceramics

The relationships between mechanical properties of Si3N4/BN multilayer materials and the geometrical factors, number of layers (N) and layer thickness ratio (λh), have been studied. At a given number of layers, with the increase of layer thickness ratio, the toughness and bending strength both increase, and when it continues to increase, the two curves both level off. Keeping the layer thickness ratio of about 10 and increasing the number of layers, the bending strength decreases slightly, and a maximum toughness was obtained at N≈30. Furthermore, a mechanical model was established and used to analyze the above experimental results. According to the experimental and calculated results, suitable geometrical parameters were advised in the design of Si3N4/BN multilayer materials as λh≈10 and N≈30.