Modeling brittle and tough stress–strain behavior in unidirectional ceramic matrix composites

Curtin, W.A.; Ahn, Byung Ki; Takeda, Nobuo

doi:10.1016/s1359-6454(98)00041-x

Cited by 204 publications

(97 citation statements)

References 25 publications

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“…To model the stress-strain response of ceramic matrix composites, knowledge of the stress-dependent number of matrix cracks is essential [18][19][20][21].…”

Section: Discussionmentioning

confidence: 99%

“…where, oC is the composite stress, 0 t h is the residual compressive stress in the matrix [19] which was found to be higher, in general, for higher volume fraction composites with inside debonding [123, and E, is the measured composite elastic modulus from the O/E curve. Figure 5 shows the estimated stress-dependent matrix crack distribution versus bminimatrix.…”

Section: Standard Sinole Tow Woven Comnmentioning

confidence: 99%

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Stress-dependent matrix cracking in 2D woven SiC-fiber reinforced melt-infiltrated SiC matrix composites

Morscher

2004

Composites Science and Technology

154

133

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The matrix cracking of a variety of SiC/SiC composites has been characterized for a wide range of constituent variation. These composites were fabricated by the 2-dimensional lay-up of 0/90 five-harness satin fabric consisting of Sylramic fiber tows that were then chemical vapor infiltrated (CVI) with BN, CVI with Sic, slurry infiltrated with Sic particles followed by molten infiltration of Si. The composites varied in number of plies, the number of tows per length, thickness, and the size of the tows. This resulted in composites with a fiber volume fraction in the loading direction that ranged from 0.12 to 0.20. Matrix cracking was monitored with modal acoustic emission in order to estimate the stress-dependent distribution of matrix cracks. It was found that the general matrix crack properties of this system could be fairly well characterized by assuming that no matrix cracks originated in the load-bearing fiber, interphase, chemical vapor infiltrated Sic tow-minicomposites, Le., all matrix cracks originate in the 90' tow-minicomposites or the large unreinforced Sic-Si matrix regions.Also, it was determined that the larger tow size composites had a much narrower stress range for matrix cracking compared to the standard tow size composites.

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“…To model the stress-strain response of ceramic matrix composites, knowledge of the stress-dependent number of matrix cracks is essential [18][19][20][21].…”

Section: Discussionmentioning

confidence: 99%

Section: Standard Sinole Tow Woven Comnmentioning

confidence: 99%

Stress-dependent matrix cracking in 2D woven SiC-fiber reinforced melt-infiltrated SiC matrix composites

Morscher

2004

Composites Science and Technology

154

133

View full text Add to dashboard Cite

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“…The strain behavior of the composite with matrix cracks has been modeled with micromechanics of bridged matrix flaws [22]. From the micromechanics analysis, matrix crack density ρ is related to the interfacial shear stress τ, the residual stress σ th , and stress-strain (σ-ε) curves by…”

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confidence: 99%

Monitoring damage accumulation in ceramic matrix composites using electrical resistivity

2008

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The electric resistance of woven SiC fiber reinforced SiC matrix composites were measured under tensile loading conditions. The results show that the electrical resistance is closely related to damage and that real-time information about the damage state can be obtained through monitoring of the resistance. Such self-sensing capability provides the possibility of on-board/in-situ damage detection and accurate life prediction for hightemperature ceramic matrix composites.Woven silicon carbide fiber-reinforced silicon carbide (SiC/SiC) ceramic matrix composites (CMC) possess unique properties such as high thermal conductivity, excellent creep resistance, improved toughness, and good environmental stability (oxidation resistance), making them particularly suitable for hot structure applications. In specific, CMCs could be applied to hot section components of gas turbines [1], aerojet engines [2], thermal protection systems [3], and hot control surfaces [4]. The benefits of implementing these materials include reduced cooling air requirements, lower weight, simpler component design, longer service life, and higher thrust [5]. It has been identified in NASA High Speed Research (HSR) program that the SiC/SiC CMC has the most promise for high temperature, high oxidation applications [6].One of the critical issues in the successful application of CMCs is on-board or insitu assessment of the damage state and an accurate prediction of the remaining service life of a particular component. This is of great concern, since most CMC components envisioned for aerospace applications will be exposed to harsh environments and play a key role in the vehicle's safety. On-line health monitoring can enable prediction of remaining life; thus resulting in improved safety and reliability of structural components. Monitoring can also allow for appropriate corrections to be made in real time, therefore leading to the prevention of catastrophic failures. Most conventional nondestructive evaluation (NDE) techniques such as ultrasonic C-scan, x-ray, thermography, and eddy current are limited since they require structural components of complex geometry to be taken out of service for a substantial length of time for post-damage inspection and assessment. Furthermore, the typical NDE techniques are useful for identifying large interlaminar flaws, but insensitive to CMC materials flaws developed perpendicular to the surface under tensile creep conditions. There are techniques such as piezoelectric sensor [7,8], and optical fiber [9,10] that could be used for on-line health monitoring of CMC structures. However, these systems involve attaching an external sensor or putting special fibers in CMC composites, which would be problematic at high temperature applications.https://ntrs.nasa.gov/search.jsp?R=20080047468 2018-05-11T18:03:58+00:00Z Most composite materials are multifunctional materials in which the damage is coupled with the material electrical resistance, providing the possibility of real-time information about the damage state thro...

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“…Where ρ plays (at fixed φ) a more important role is where elongations are low: there, its influence can be considerable, as shown by the high slope of the iso-deformation lines or by the increase in tensile elongation that is, for example, brought by going from ρ = 7 to ρ = 15 when φ equals 10 12 : the ductility then goes roughly from 1 to 10%. Table 2 gives relevant physical properties of a few brittle metals in which fracture statistics have been reported in the form of two-parameter Weibull statistics (often, three-parameter Weibull statistics are given instead [31,32,35,37,[46][47][48][49][50][51][52][53][54]); note that these are often for deformation at temperatures well below ambient. Let us consider a "typical" medium-strength brittle steel, with E = 210 GPa, σ 0 = 1,500 MPa and L 0 = 1 m, leaving the Weibull parameter ρ as a free-floating variable.…”

Section: Engineering Implicationsmentioning

confidence: 99%

Tensile elongation of unidirectional or laminated composites combining a brittle reinforcement with a ductile strain and strain-rate hardening matrix

Cohades¹,

Mortensen²

2014

Acta Materialia

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We use the long-wavelength model of Hutchinson and Neale (Hutchinson JW, Neale KW. Acta Metall 1977;25:839) and Ghosh (Ghosh AK. Acta Metall 1977;25:1413) to estimate the uniform tensile elongation of two-phase composites deforming quasistatically according to the equistrain rule of mixtures, in which one phase is ductile while the other fractures progressively according to twoparameter Weibull statistics. We use shear-lag models in the literature to quantify load transfer from the ductile phase to the fractured brittle phase, to estimate the influence of matrix strain and strain-rate hardening, of brittle phase fracture characteristics, and of phase volume and strength ratios, on the composite strain to failure as dictated by the onset of unstable necking. Calculations show that strain and strain-rate hardening of the ductile phase do relatively little to increase the ductility of the composite. Two parameters play a dominant role, namely the brittle phase Weibull modulus and a dimensionless parameter describing load transfer across the two phases. The main practical implication of this analysis is that, to produce reasonably ductile two-phase composites, the best strategy is to aim for small layer thicknesses. IntroductionMany composite materials combine a ductile matrix with a brittle reinforcement: ceramic or carbon fibre reinforced metals fall in this category, as do some laminated metal composites and many other layered materials (such as thin film structures or ceramic-coated metals) [1][2][3][4]. When such composites are strained in tension the brittle phase develops cracks that cut its fibres or layers in two along a plane normal to the applied load; in laminated composites these are known as "tunnel cracks". Final fracture of the material may then happen in one of two ways. One is sudden brittle failure, caused by a propagative localization of internal damage that cuts abruptly the entire specimen in two; many strongly bonded ceramic or carbon fibre reinforced composites fail in this way [5][6][7], as do some particle reinforced composites [8]. Alternatively, internal damage accumulates stochastically throughout the material, in gradual and uncorrelated fashion. The composite is then likely to fail by strain localization, reaching its ultimate tensile strength at a smooth maximum along its stress-strain curve, and sometimes deforming significantly thereafter, while deformation concentrates in a portion of the sample's gauge length. Weakly bonded fibre reinforced composites (e.g., [5]), ceramic particle reinforced metals (e.g., [8,9]), two-phase metal alloys [10] or laminated metal composites [11] can all fail in this way. Strain hardening and strain-rate hardening then both play an important role: even small increases in a ductile material's strain hardening rate, or in its strain-rate sensitivity, can noticeably increase the tensile elongation when it is governed by the onset of strain localization.

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Modeling brittle and tough stress–strain behavior in unidirectional ceramic matrix composites

Cited by 204 publications

References 25 publications

Stress-dependent matrix cracking in 2D woven SiC-fiber reinforced melt-infiltrated SiC matrix composites

Stress-dependent matrix cracking in 2D woven SiC-fiber reinforced melt-infiltrated SiC matrix composites

Monitoring damage accumulation in ceramic matrix composites using electrical resistivity

Tensile elongation of unidirectional or laminated composites combining a brittle reinforcement with a ductile strain and strain-rate hardening matrix

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