Influence of specimen geometry and relative crack size on the R-curve

The material property responsible for increasing crack growth resistance in monolithic ceramics is the relation between the bridging stresses in the wake of a crack and the actual crack face separation. By analytical and numerical computations, it is shown how crack resistance curves (R-curves) are strongly influenced by test specimen geometry and the relative crack length. As a result of these considerations, it is concluded that the R-curve for small crack extensions may be considered a true material property. However, this is not true for large crack lengths where the influence of geometric data becomes important. (C) 2000 Elsevier Science Ltd. All rights reserved.