FRACTURE-BEHAVIOR OF DIRECTIONALLY SOLIDIFIED Y3AL5O12 AL2O3 EUTECTICFIBER/

The strength and fracture of a directionally solidified Y3Al5O12/Al2O3 eutectic fiber were investigated. The fiber was grown continuously by an edge-defined film-fed growth technique. The microstructure was cha racterized using X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The tensile strength and Weibull's mod ulus of the eutectic fibers were determined in the as-fabricated state and after extended thermal exposure at 1460 degrees C in air. Fractog raphic analysis was used to identify and classify the strength-limitin g mechanisms. The fracture toughness and crack growth behavior were ch aracterized by an indentation technique. A fracture mechanics analysis was also used to establish the relationships between surface flaw siz e, tensile strength, and fracture toughness of the fiber.