The Regents of the University of California Santa Barbara United States
The use of fugitive coatings to produce controlled, uniform interface gaps in oxide composites has been assessed. The results demonstrate that thenotched and unnotched tensile properties of gap-containing materials are superior to those of materials with bonded interfaces, especially after long-term1000 h aging at targeted service temperatures 1200C. The thermochemical stability of these materials represents a significant advancement toward the goal of enhanced durability. Additionally, processing principles and implementation protocols for producing 3D oxide composites with high-integrity matrices have been established. Shrinkage cracks in these matrices has been mitigated through the addition of comparatively large particles to the matrix pockets between tows. The concept has been demonstrated using SiC, although extensions to other particle types e.g. mullite should, in principle, be feasible. Finally, upon expanding collaborations with AFRL personnel, the efficacy of monazite coatings in the toughness and durability of 3D composites with aluminamullite fibers has been initiated.