Matrix fracture energy as a function of porosity for all oxide ceramic matrix composites

This study presents an easy way to investigate the suitability of a porous material as a matrix for a weak matrix composite (WMC) according to the model of He and Hutchinson without the use of expensive fibers. The influence of porosity on the fracture energy of a monolithic alumina-zirconia matrix system developed for an all-oxide ceramic matrix composite (Ox/Ox) was used to compare theoretical predictions with the real Ox/Ox behavior´, which we presented in our previous study. The Ox/Ox material used for the comparison was a combination of α-alumina Nextel™ 610 fibers embedded in the said alumina-zirconia matrix system. The matrix fracture energy was determined on monolithic samples using a three-point-bending test, based on the work-of-fracture approach. By using the ratio between the determined fracture energy and the fracture energy of dense alumina fibers, it was possible to classify our material in the theoretical model. The results showed, that the method allowed a precise prediction of the damage-tolerant behavior of a CMC, thereby enabling the development of future matrix materials by using solely monolithics.