Effective elastic moduli of fiber-matrix interphases in high-temperature composites
- Ohio State Univ., Columbus, OH (United States). Dept. of Industrial, Welding, and Systems Engineering
This article describes a theoretical model and an experimental method for determination of interphasial elastic moduli in high-temperature composites. The interphasial moduli are calculated from the ultrasonically measured composite moduli via inversion of multiphase micromechanical models. Explicit equations are obtained for determination of interphasial stiffnesses for an interphase model with spring boundary conditions and multiphase fiber. The results are compared with the exact multiphase representation. The method was applied to ceramic and intermetallic matrix composites reinforced with SiC SCS-6 fibers. In both composites, the fiber-matrix interphases include approximately 3-{micro}m-thick carbon-rich coatings on the outer surface of the SiC shell. Although the same fiber is used in both composite systems, experimental results indicate that the effective interphasial moduli in these two composite systems are very different. The interphasial moduli in intermetallic matrix composites are much greater than those in ceramic matrix composites. After taking the interphase microstructure into account, the authors found that the interphasial moduli measured for the intermetallic matrix composites are very close to the estimated bulk moduli of the pyrolytic carbon with SiC particle inclusions. The analysis shows that the lower effective interphasial moduli in the reaction-bonded Si{sub 3}N{sub 4} (RBSN) ceramic matrix composites are due to imperfect contact between the interphasial carbon and the porous matrix and to thermal tension forces which slightly unclamp the interphase. Thus, measured interphase effective moduli give information on the quality of mechanical contact between fiber and matrix.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 203528
- Journal Information:
- Metallurgical Transactions, A, Vol. 27, Issue 1; Other Information: PBD: Jan 1996
- Country of Publication:
- United States
- Language:
- English
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