Fracture mechanisms and mechanics of fiber-reiforced ceramic composites.

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The major focus of the research project is on the strengthening and toughening microfracture processes and mechanisms of fiber-reinforced ceramic matrix composites through theoretical as well as experimental considerations. The results of investigations have been reported through ten technical papers published mainly in major international journals.It is emphasized in this project that the most essential microfracture processes and mechanisms which controls the fracture toughness and strength of fiber-reinforced composites are; (a) first matrix cracking, (b) crack-face fiber bridging behind the crack-tip, and (c) pulling broken fibers out of matrix. Pertinent experimental techniques and theoretical considerations have been developed in this project for quantitatively analyzing these microfracture processes. They have been applied to the fracture of; (a) a unidirectionally reinforced carbon-fiber/carbon=matrix composite, (b) two-dimentionally reinforced carbon-fiber/carbon-matrix composites, and (c) carbon-fiber/silicon nitride-matrix composites having reinforcing fibers with different thicknesses (diameters).Based on the experimental and theoretical results, materials design for structural ceramic composites with improved strength and toughness was conducted.