Simplified micromechanical equations for thermal residual stress analysis of coated fiber composites

Technical Report · Sun Sep 01 04:00:00 EDT 1991

OSTI ID:6169756

Naik, R A

The fabrication of metal matrix composites poses unique problems to the materials engineer. The large thermal expansion coefficient (CTE) mismatch between the fiber and matrix leads to high tensile residual stresses at the fiber/matrix (F/M) interface which could lead to premature matrix cracking during cooldown. Fiber coatings could be used to reduce thermal residual stresses. A simple closed form analysis, based on a three phase composite cylinder model, was developed to calculate thermal residual stresses in a fiber/interphase/matrix system. Parametric studies showed that the tensile thermal residual stresses at the F/M interface were very sensitive to the CTE and thickness of the interphase layer. The modulus of the layer had only a moderate effect on tensile residual stresses. For a silicon carbide titanium aluminide composite, the tangential stresses were 20 to 30 pct. larger than the axial stresses, over a wide range of interphase layer properties, indicating a tendency to form radial matrix cracks during cooldown. Guidelines for the selection of appropriate material properties of the fiber coating were also derived in order to minimize thermal residual stresses in the matrix during fabrication.

• Research Organization: Analytical Services and Materials, Inc., Hampton, VA (United States)
• OSTI ID: 6169756
• Report Number(s): N-91-32527; NASA-CR--187599; NAS--1.26:187599; CNN: NAS1-18599
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
360606 -- Other Materials-- Physical Properties-- (1992-)
CARBIDES
CARBON COMPOUNDS
COATINGS
COMPOSITE MATERIALS
ELEMENTS
EXPANSION
FABRICATION
FIBERS
MATERIALS
MATRIX MATERIALS
MECHANICAL PROPERTIES
METALS
SILICON CARBIDES
SILICON COMPOUNDS
STRESS ANALYSIS
STRESSES
TENSILE PROPERTIES
THERMAL EXPANSION
THERMAL STRESSES
TITANIUM
TRANSITION ELEMENTS