Micromechanical stresses in monolithic ceramics and ceramic composite materials

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:7249834

Li, Z

By developing a modification of the Eshelby method and applying it in matrix form, the micromechanical stresses and strain energy density within polycrystalline ceramics and ceramic matrix composites have been determined. For cubic polycrystalline ceramics the micromechanical stress concentration and the strain energy density are related to the elastic anisotropy of individual large grains within a fine grain size microstructure. Those large grains are ideal sites for fracture initiation, directly influencing the strength of cubic polycrystalline ceramics. Micromechanical stresses and strain energy densities of noncubic polycrystalline ceramics are not only dependent on the elastic anisotropy, but also on the thermal-expansion anisotropy. Even without external loading, internal stresses are generated during temperature changes and may result in spontaneous microcracking. Besides the thermoelastic anisotropy, the geometry of the crystals or grains is also important and influences the micromechanical stresses within polycrystalline ceramics. Micromechanical stresses in SiC-reinforced ceramic-matrix composites are often in the GPa range and may be expected to influence the strength, fracture toughness and the R-curve behavior.

• Research Organization: Washington Univ., Seattle, WA (USA)
• OSTI ID: 7249834
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
360603 -- Materials-- Properties
CARBIDES
CARBON COMPOUNDS
CERAMICS
COMPOSITE MATERIALS
CRYSTALS
ENERGY DENSITY
GEOMETRY
MATERIALS
MATHEMATICS
MATRIX MATERIALS
POLYCRYSTALS
REINFORCED MATERIALS
SILICON CARBIDES
SILICON COMPOUNDS
STRAINS
STRESS ANALYSIS