Elastic/plastic analyses of advanced composites investigating the use of the compliant layer concept in reducing residual stresses resulting from processing
High residual stresses within intermetallic and metal matrix composite systems can develop upon cooling from the processing temperature to room temperature due to the coefficient of thermal expansion (CTE) mismatch between the fiber and matrix. As a result, within certain composite systems, radial, circumferential, and/or longitudinal cracks have been observed to form at the fiber-matrix interface. The compliant layer concept (insertion of a compensating interface material between the fiber and matrix) was proposed to reduce or eliminate the residual stress buildup during cooling and thus minimize cracking. The viability of the proposed compliant layer concept is investigated both elastically and elastoplastically. A detailed parametric study was conducted using a unit cell model consisting of three concentric cylinders to determine the required character (i.e., thickness and material properties) of the compliant layer as well as its applicability. The unknown compliant layer mechanical properties were expressed as ratios of the corresponding temperature dependent Ti-24Al-11Nb (a/o) matrix properties. The fiber properties taken were those corresponding to SCS-6 (SiC). Results indicate that the compliant layer can be used to reduce, if not eliminate, radial and circumferential residual stresses within the fiber and matrix and therefore also reduce or eliminate the radial cracking. However, with this decrease in in-plane stresses, one obtains an increase in longitudinal stress, thus potentially initiating longitudinal cracking. Guidelines are given for the selection of a specific compliant material, given a perfectly bonded system.
- Research Organization:
- National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
- OSTI ID:
- 6333625
- Report Number(s):
- N-91-11074; NASA-TM-103204; E-5661; NAS-1.15:103204
- Country of Publication:
- United States
- Language:
- English
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Reduction of thermal residual stresses in advanced metallic composites based upon a compensating/compliant layer concept
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Related Subjects
COMPOSITE MATERIALS
STRESS ANALYSIS
ALUMINIUM ALLOYS
COOLING
CRACK PROPAGATION
FIBERS
FINITE ELEMENT METHOD
INTERMETALLIC COMPOUNDS
MATRIX MATERIALS
NIOBIUM ALLOYS
SILICON CARBIDES
TEMPERATURE DEPENDENCE
TEMPERATURE EFFECTS
THERMAL EXPANSION
TITANIUM BASE ALLOYS
ALLOYS
CARBIDES
CARBON COMPOUNDS
EXPANSION
MATERIALS
NUMERICAL SOLUTION
SILICON COMPOUNDS
TITANIUM ALLOYS
360603* - Materials- Properties