R-CURVE MODEL OF CERTAIN CERAMIC COMPOSITES

Abstract— The influence of crack-bridging on the R -curve for certain types of ceramic composites is modeled. Small scale bridging conditions are assumed. A recurrence procedure is used to solve the governing coupled integral equations, resulting in R -curves (stress intensity factor versus crack growth) that depend on well defined microstructural parameters. In addition, the bridging stresses and the crack opening diplacements were computed for all stages of the R -curve development. The numerical scheme is quite general and can be used for a variety of bridging laws. The convergence of the solution method is uniform, and the accuracy is a priori controlled. The results are normalized so that they can be applied for a large variety of composites with different micromechanical parameters. R -curves were computed for different bridiging laws, and were found to be sensitive to the specific bridging law used each time. Some strength-toughness relations are also discussed. The results are particularly suitable for slow crack growth analysis.