Effect of Aging and Composition on Mechanical Properties of Mullite/Alumina Porous Mixtures for Use as Porous Matrices in Oxide Fiber Composites

Abstract

Weakly bonded particle mixtures of mullite and alumina are assessed as candidate matrices for use in porous matrix ceramic composites. The experimental study focuses on the modulus and toughness of the particle mixtures as well as the changes in these properties following aging at elevated temperature, comparable to the targeted upper use temperature for oxide composites. Models based on bonded particle aggregates are presented, assessed and calibrated. The experimental and modeling results are combined to predict the critical aging times at which damage tolerance is lost because of sintering at the particle junctions and the associated changes in mechanical properties. For an aging temperature of 1200°C, the critical time exceeds 10,000 hours for the mullite-rich mixtures.