Crack deflection in ceramic laminates using porous interlayers

Ceramic laminates have been made from alternating layers of silicon carbide and silicon carbide containing a fugitive polymer, which can be pyrolysed to produce porous interlayers. It is shown that such interlayers can be used to deflect cracks and that the volume fraction of porosity, due to the added polymer, that is required to cause crack deflection is approximately 0.4. A simple model has been developed which describes the fracture behaviour of porous solids and also predicts the volume fraction of porosity required to give crack deflection in the laminate and which is in good agreement with experiment. (C) 1998 Elsevier Science Limited. All rights reserved.