Simulation of crack propagation in alumina particle-dispersed SiC composites

Addition of alumina particles to silicon carbide results in strongly improved toughness values. In order to come to a better understanding of this phenomenon, crack propagation is simulated for a 20 vol% alumina particles-dispersed silicon carbide composite material using the Body Force Method. Special emphasis is paid to the influence of graded compositions. Numerically obtained crack paths are compared to crack paths generated experimentally by Vickers indentations. Moreover, mechanical properties of the investigated material were measured experimentally. Microstructural toughness variations as well as the direction of crack propagation are found to be strongly influenced by residual stresses due to the mismatch between thermal expansion coefficients of alumina and silicon carbide and by the actual crack location. According to tensile residual stresses in the radial direction cracks approaching a particle are deviated circumferentially in the matrix around the particle. Moreover, the failure behavior of cracks propagating into a zone of increasing or decreasing volume fraction of alumina particles is found to behave differently as residual stress fields superimpose in the case of particle clustering. (C) 1999 Elsevier Science Limited. All rights reserved.