Bridging stresses and R-curves in ceramic/metal composites

Incorporation of metal into brittle ceramics results in an increase in fracture toughness, which can lead to an increase in strength, reliability and thermal shock resistance of the composite compared to monolithic ceramics. The basic material specific property, which controls the enhancement of the mechanical properties, is the bridging stress relation of the metal reinforcements. This relation was calculated from measured profiles of loaded cracks (COD) for fiber reinforced model composites and interpenetrating network composites in the system Al2O3/Al. Results are compared with directly measured bridging stress relations for the model materials. The bridging relations are further used to model the R-curve behavior of the composites which are compared with experimentally measured ones. Limitations of the applied procedure are discussed as well as the influence of specimen geometry and flaw size.