Radial variations in modulus and hardness in SCS-6 silicon carbide fibers

Journal Article · Fri Jan 01 04:00:00 EST 1999 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1999.tb01730.x· OSTI ID:316022

Mann, A B; Weihs, T P ^[1]; Balooch, M; Kinney, J H ^[2]

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1. Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Materials Science and Engineering
2. Lawrence Livermore National Lab., CA (United States). Dept. of Chemistry and Materials Science

The mechanical properties of SCS-6 SiC fibers were measured as a function of fiber radius using nanoindentation techniques. Hardness and Young`s modulus were characterized for the material in all of the major regions of these fibers: the carbon core, the graphitic core coating, the inner SiC sheath, and the outer SiC sheath. The carbon core of the fibers was determined to be uniform in properties but extremely compliant. Young`s modulus of 28 GPa and a hardness of 4.2 GPa were measured. The graphitic core coating was found to exhibit considerable anelasticity and to have both a low modulus (21 GPa) and a low hardness (1.7 GPa). The inner sheath of the fiber, which contained a varying chemistry, showed a sharp increase in stiffness and hardness from the inner core. Modulus and hardness increased by an order of magnitude over just 1 or 2 {micro}m when transversing radially away from the core into the SiC. This change in properties was pronounced and clearly defined. The outer sheath, which contained a uniform chemistry and microstructure, was consistently stiff and hard when transversing radially. The average modulus and hardness for the full fiber was 333 GPa. The values reported for Young`s modulus and hardness clearly showed that the mechanical properties of SCS SiC fibers exhibit dramatic changes across their diameters.

• Sponsoring Organization: USDOE, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 316022
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 1 Vol. 82; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBON
COATINGS
COMPOSITE MATERIALS
FIBERS
GRAPHITE
HARDNESS
SILICON CARBIDES
VARIATIONS
YOUNG MODULUS