Toughening of layered ceramic composites with residual surface compression: effects of layer thickness

Shielding of edge cracks in multilayer single-edge-notch-bend (SENB) specim ens, with alternating layers designed to produce residual compression and b alancing tension, was calculated by the method of weight function. Investig ation of the effects of the relative thickness of the layers and of the num ber of layers revealed that the maximum crack shielding and the maximum app arent fracture toughness were achieved in three-layer composites with the t hickness of the compression layer constituting one-half of the specimen hei ght with an edge crack extending to the first interface. These theoretical predictions were confirmed with measurements of apparent fracture toughness in the range, 28-32 MPa rootm, on three-layer SENB specimens of alumina-zi rconia composites. (C) 2000 Published by Elsevier Science Ltd.