Functionally Graded Jolnts For Carbonicarbon Composites I. Micro-Raman Spectroscopy Characterization

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Joining C-C composites has been a subject for extensive research for the last decade. It is essential that the joint have the requisite strength and toughness at high temperatures as well as a low CTE to match the C-C base material. Two major subjects have evolved recently that would have a profound impact on the field of C-C composite joining; the ternary carbide Ti,SiC, as a new ternary carbide system that exhibit unique mechanical and thermal properties, and the evolution of Micro-Raman Spectroscopy (MN) as a micromechanical measurements technique capable of measuring stresses with a spatial resolution of 1 pm In this paper, the power of tbe MRS technique in characterizing C-C composite joints is demonstrated, Ternary carbide alloy (Ti,SiCJ was reacted with a flat panel of Z-D Carbon-Carbon composite. MRS was used to characterize the composition within the reaction zone (30 pm thick) and to measure residual stresses in the C-C composite and the ternary carbide around the reaction zone. It was found that the ternary carbide consumes the C-C composite within the reaction zone and generates a new Tic/Sic composite. The concentration of the ternary carbide within the reaction zone was found to decrease lineady towards the C-C composite. The stresses in the ternary carbide were found to be tensile and increased linearly within the reaction zone. Stresses created in the C-C composite were compressive and decreased IinearIy away from the reaction zone.

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