Selected issues of mechanics of ceramic matrix composites
Introduction
Ceramic matrix composites (CMC) are attractive in applications, where high temperature and/or damage tolerance are important. Typical applications include internal chambers and nozzles of jet motors, turbine nozzles, aircraft brakes, etc. [1], [2], [3], [4], [5].
A unique feature of CMC is related to their ability to withstand initial damage without immediate failure. The reasons are a deflection of matrix cracks at the fiber–matrix interfaces and a redistribution of stresses in the area of high stress concentration due to a nonlinear stress–strain behavior. This makes a study of damaged CMC particularly important, the purpose of such research is to predict the properties of a damaged CMC component and to estimate its remaining life. Extensive literature has been published to address these problems and a recent review of the authors [6] contains an outline of the state of art in some of related areas.
The present paper illustrates an approach to the solution of four important problems:
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Stiffness of a unidirectional lamina with bridging matrix cracks.
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Nonlinear stress–strain behavior of a unidirectional lamina subject to a monotonically increasing load in the presence of developing matrix cracks.
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Free and forced small-amplitude vibrations of plain-weave woven CMC beams with pre-existing matrix cracks.
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Surface temperature of plain-weave woven CMC beams with matrix cracks due to frictional heating during forced vibrations (feasibility of using thermography).
Section snippets
Stiffness of a unidirectional lamina with bridging matrix cracks
The modulus of elasticity of a unidirectional lamina with the fibers oriented in the x-direction in the presence of bridging cracks and subjected to axial stresses can be obtained according to Pryce and Smith [7]. Byrd and Birman [8] modified this modulus for a lamina with matrix cracks that emerged during post-processing cooling and affected residual stresses. The expressions for these moduli can be combined yieldingwhere the subscripts identify
Conclusions
This paper illustrates four representative problems of mechanics of CMC with matrix cracks. The first problem is related to identifying material constants and the matrix of stiffnesses of a unidirectional lamina with bridging cracks. The assumption that the stiffness in the planes perpendicular to the fibers remains unaffected by the cracks enables us to specify all material constants in both plane stress and three-dimensional formulations. The second solution refers to a nonlinear behavior of
Acknowledgements
This research was supported by the Air Force Office of Scientific Research through the contract F49620-93-C-0063. The program manager is Dr. Brian Sanders.
References (16)
- et al.
Matrix cracking in unidirectional ceramic matrix composites under quasi-static and cyclic loading
Acta Metallurgica et Materialia
(1993) - et al.
Detection of cracks in ceramic matrix composites based on surface temperature
Compos Struct
(2000) - et al.
Thermostructural CMCs: an overview of the French experience
- et al.
CMC intake ramp for hypersonic propulsion systems
- Ortiz M, Bergeron D, Brown R, Chung V, Bhatt RT. Ceramic matrix composite nozzle development. HITEMP Review 1997....
- et al.
Military turbojet component design and validation with thermostructural composite material
- et al.
Ceramic matrix composites applications in automotive gas turbines
J Eng Gas Turbines Power
(1997) - Birman V, Byrd LW. Review of fracture and fatigue in ceramic matrix composites. Report AFRL-VA-OP-TR-1999–3023,...
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