Elevated temperature crack growth resistance of alumina-silicon-carbide composite under static and cyclic loads

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:5566438

Han, X

The crack growth behavior in ceramic composites was studied. The study showed that permanent fatigue damage and stable crack growth in cyclic compression can occur in Si{sub 3}N{sub 4}-SiC(w) composites at room temperature. The principal mechanisms of the failure are discussed. During compressive stress, extensive inelastic deformation is induced in the vicinity of the notch root. If this deformation leaves permanent strain, upon unloading from the compressive stress, a residual tensile stress zone is created at the notch-tip. When the tensile stress exceeds the strength of the material, Mode 1 fatigue crack growth occurs. It was also shown that stable high temperature crack propagation can occur in Al{sub 2}O{sub 3}-SiC(w) under both static and cyclic tensile loads at stress intensity values far below the fracture toughness. The origin of permanent inelastic deformation and creep fatigue crack growth appears to be interfacial and intergranular cavitation produce pronounced microcracking in the composite. This cavitation mechanism is promoted by the oxidation of SiC whiskers in the high temperature air environment, leading to the formation and viscous flow of an SiO{sub 2} glassy phase along the SiC-Al{sub 2}O{sub 3} interface. Cyclic fatigue behavior needs study.

• Research Organization: Brown Univ., Providence, RI (United States)
• OSTI ID: 5566438
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
COMPOSITE MATERIALS
CRACK PROPAGATION
DEFORMATION
FATIGUE
FRACTURE PROPERTIES
GLASS
MATERIALS
MECHANICAL PROPERTIES
NITRIDES
NITROGEN COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PNICTIDES
SILICON CARBIDES
SILICON COMPOUNDS
SILICON NITRIDES
STATIC LOADS
STRESS ANALYSIS
STRESS INTENSITY FACTORS
TEMPERATURE EFFECTS