Quantification of Higher SiC Fiber Oxidation Rates in Presence of B
            <sub>2</sub>
            O
            <sub>3</sub>
            Under Air

Rebillat, F.; Garitte, E.; Guette, A.

doi:10.1002/9780470909836.ch13

Cited by 8 publications

(27 citation statements)

References 13 publications

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“…Using the 1200˚C kp for CVD-SiC reported by Ogbuji and Opila 17 , it would take 9.9 h to grow an equivalent SiO2 oxide thickness. This order of magnitude increase in SiC oxidation kinetics is in line with others 23,39,41 who also observed orders of magnitude increases in the oxidation kinetics of Si-based materials due to the presence of B2O3.…”

Section: Oxidation Resultssupporting

confidence: 91%

“…Linear reaction rate constants (kl), given by the slopes of the linear weight gain, are reported in Table 5. The weight change profiles exhibited parabolic oxidation kinetics for exposures ≥ 1100˚C, consistent with diffusion controlled oxidation kinetics 23 . Although the Sylramic fibers generally followed the Deal and Grove oxidation kinetic model 22 , the deviations in the weight change profiles were attributed to oxidation effects from the B4C and TiB2 constituents.…”

Section: Oxidation Resultssupporting

confidence: 72%

“…Representative Sylramic fiber TGA traces were plotted as specific weight change versus time from isothermal oxidation exposures at temperatures ranging from 800 -1300˚C, as shown in Figure 23. The weight gain was linear for exposures from 900 -1000˚C, signifying that the fiber oxidation kinetics were surface -reaction controlled 23 .…”

Section: Oxidation Resultsmentioning

confidence: 89%

“…This section closes by including oxidation studies in which accelerated oxidation of Si-based systems was observed when boron (B) was present. 23 , where x is the oxide thickness and t is time:…”

Section: Oxidation Studies On Cmc Componentsmentioning

confidence: 99%

“…The parabolic oxidation rate constant is represented by kp, which is related to the product of the oxidant diffusivity, Deff, through the oxide and the solubility of the oxidant in the oxide, C*, as given by Equation 12 The SiC oxidation rate constants calculated from oxide thickness measurements can be converted to rate constants calculated from weight change measurements since the overall weight gain is derived from the oxidation reaction (i.e., in the case of the oxidation of SiC the overall weight gain is the difference between the gain in two oxygens and loss of one carbon) 23,24 . When oxidation is accompanied by volatilization reactions, the use of weight change can be applied only when contributions to the overall weight change from the volatilizing species are negligible.…”

Section: Oxidation Studies On Cmc Componentsmentioning

confidence: 99%

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Boria Effects on the High Temperature Oxidation of Silicon Carbide

McFarland¹

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Section: Oxidation Resultssupporting

confidence: 91%

Section: Oxidation Resultssupporting

confidence: 72%

Section: Oxidation Resultsmentioning

confidence: 89%

Section: Oxidation Studies On Cmc Componentsmentioning

confidence: 99%

Section: Oxidation Studies On Cmc Componentsmentioning

confidence: 99%

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Boria Effects on the High Temperature Oxidation of Silicon Carbide

McFarland¹

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Damage and Lifetime Modeling for Structure Computations

Baranger

Genet

Cluzel

2014

Ceramic Matrix Composites

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INTRODUCTIONCeramic matrix composites (SiC fibers, PyC interphase, and mutistacked Si-B-C matrix in this paper) combine good mechanical properties with the capability of sustaining high temperatures in oxidizing environments. The use of a multilayer self-healing matrix improves the lifetime of ceramic matrix composites (CMCs) considerably [1]. This technology along with the use of SiC fibers paves the way for applications with very long lifetimes (several thousands of hours).Structural applications of CMCs need to answer to the main and critical question that is at the center of this chapter: how to predict, that is, to compute, the lifetime of engineering structures. The answer is a multiphysic macroscopic model able to reproduce couplings between the mechanical and environmental fields. For such materials, confidence in the simulation is related directly to one's understanding of each degradation mechanism and to the introduction of such mechanisms in the model; lifetimes being too large for a purely experimental validation over long lifetimes (tens of thousands of hours).The first part of the chapter deals with the modeling of the different microcracking mechanisms. The key phenomenon is the deflection of the matrix cracks in the fiber matrix interphase [2][3][4]: this mechanical fuse protects the fibers from the cracks and enables the development of multiple cracks in the matrix, giving the composite some level of ductility, even though all of its constituents are brittle. The matrix cracking scenario has already been established for woven CMCs [5]. Since the matrix between the yarns is stiffer, but more brittle, and has larger pores than the yarns themselves, it begins to crack first. For a well-densified composite, the corresponding cracks are oriented by the main loading direction and are orthogonal to the applied stress direction, which is a main modeling difficulty. Then, when this crack network nearly reaches saturation, new cracks mainly appear in the matrix inside the yarns. The corresponding cracks are oriented by the fibers: they are orthogonal to the fibers in the longitudinal yarns, and parallel to the fibers in transverse yarns if the main load direction corresponds to the longitudinal yarns. In summary, there are three types of cracks in the damaged material: (i) inter-yarn cracks, (ii) intra-yarn longitudinal cracks, and (iii) intra-yarn transverse cracks.Among composites, CMCs are the most difficult situation for damage modeling. Rather complex closure effects occur for the damage mechanism associated with microcracks when direction is orthogonal to the loading direction and, therefore, is not known a priori. Here, we are developing our answer with a general anisotropic damage theory including microcracks closure effects [6,7]. In order to differentiate between the crack opening and closing effects, which are very pronounced in CMCs, the strain energy is divided into three parts associated with damage due to pure traction, Ceramic Matrix Composites: Materials, Modeling and Technology, First Ed...

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Modeling framework and associated simulation tools for the prediction of damage tolerance of CMC

Baranger

2015

MATEC Web of Conferences

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Abstract.A modeling framework and the associated simulation tools are presented for the prediction of the mechanical behaviour and lifetime of CMC with self-healing matrix. A macroscopic anisotropic damage model enriched with micro information has been developed, identified and validated using experimental information at different levels including reaction kinetics, fiber failure probability or macroscopic mechanical behavior. The computational cost associated to the proposed model being quite expansive, a method has been setup to construct, automatically, reduced numerical constitutive laws. An illustration is given as well as the associated error estimation.With high manufacturing costs and moderated lifetimes at high temperatures, the use of CMC has been limited to military engine application. Nevertheless, recent developments on self-healing matrices have greatly increase their properties for long lifetimes. It is now possible to use them on civil engine applications in order to improve engine temperatures [1].A first family of models have been developped to predict the mechanical behaviour of CMC under static loadings at the macroscopic scale [2][3][4]. For low lifetimes up to 5 000 h, a purely experimental approach allowed, for a high cost, to handle the problem of certification in the military domain. For civil application (expected lifetimes greater than 50 000 h) within the framework of damage tolerance, a direct experimental strategy becomes unaffordable. It becomes necessary to use models in order to anticipate the long term behavior over the whole loading range. A second family of models has been developed at . The aim of these models is to predict the mechanical behavior but also the lifetime of the material. Loading cases accounted for in the model are static or cyclic mechanical loadings has well as thermal and chemical loadings (oxygen and steam pressures). To get robust results under multi-axial and multiphysic loadings, the model should rely on solid foundations. The aim of this paper is to present that kind of model and then how to implement and use them efficiently in a structural computation framework. First of all, note that a large amount of experimental information and models are available at different scales and on different mechanisms for this material [8][9][10]: from lifetimes on fibers to mechanical behavior on composite coupons by oxidation kinetics. a

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Quantification of Higher SiC Fiber Oxidation Rates in Presence of B ₂ O ₃ Under Air

Cited by 8 publications

References 13 publications

Boria Effects on the High Temperature Oxidation of Silicon Carbide

Boria Effects on the High Temperature Oxidation of Silicon Carbide

Damage and Lifetime Modeling for Structure Computations

Modeling framework and associated simulation tools for the prediction of damage tolerance of CMC

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Quantification of Higher SiC Fiber Oxidation Rates in Presence of B 2 O 3 Under Air

Cited by 8 publications

References 13 publications

Boria Effects on the High Temperature Oxidation of Silicon Carbide

Boria Effects on the High Temperature Oxidation of Silicon Carbide

Damage and Lifetime Modeling for Structure Computations

Modeling framework and associated simulation tools for the prediction of damage tolerance of CMC

Contact Info

Product

Resources

About

Quantification of Higher SiC Fiber Oxidation Rates in Presence of B ₂ O ₃ Under Air