Crack Growth in Solid Oxide Fuel Cell Materials: From Discrete to Continuum Damage Modeling

Nguyen, Ba Nghiep; Koeppel, Brian J.; Ahzi, Saı̈d; Khaleel, Mohammad A.; Singh, Prabhakar

doi:10.1111/j.1551-2916.2005.00874.x

Cited by 50 publications

(44 citation statements)

References 26 publications

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“…Similar to the MEA, a metallic interconnect (MIC) is a multilayer of finite durability [26], wherein, in state-of-the-art solutions, a ceramic coating slows the growth of the oxide scale of lower electrical conductivity and the vaporisation of chromium, that poisons the cathode. Fracture mechanics approaches have been applied to study the cracking of the glass-ceramic or sealing interfaces, commonly observed during thermal cycling [27,28].…”

Section: Introductionmentioning

confidence: 99%

Mechanical reliability and durability of SOFC stacks. Part II: Modelling of mechanical failures during ageing and cycling

Nakajo

Mueller

Brouwer

et al. 2012

International Journal of Hydrogen Energy

107

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Creep Contact analysis a b s t r a c tIntricate relationships between mechanical and electrochemical degradation aspects likely affect the durability of solid oxide fuel cell stacks. This study presents a modelling framework that combines thermo-electrochemical models including degradation and a contact thermo-mechanical model that considers rate-independent plasticity and creep of the components materials and the shrinkage of the nickel-based anode during thermal IntroductionThe end of operation of a solid oxide fuel cell (SOFC) stack ultimately occurs due to the loss of structural integrity of one or several of the cells, as highlighted by several short-stack experiments, e.g [1e4]. We believe this is the result of the accumulation during operation, of physico-chemical alterations inducing a weakening of the materials and interfaces, of plastic and creep deformations, and of the modification of the temperature profile, due to the degradation of the electrochemical performance of the cells. Mechanical issues do not, however, exclusively occur after prolonged use. Inappropriate control during start-up and shut-down and/or following of the electrical power demand, harsh characterisation procedures and thermal cycling can induce discrete failures [5,6]. Despite the evidence of mechanical issues in SOFCs, which are experienced even during laboratory button cell tests, this topic is still receiving limited attention. Efforts are seen as standalone tasks, owing to the different experimental and modelling techniques that are required to gather the essential information, whereas mechanical failures in SOFCs are likely intricately related to chemical and electrochemical aspects.The central component in a stack is the membrane electrode assembly (MEA). As for any multilayered system made of brittle materials, the MEA is prone to failures related to residual * Corresponding author. Tel.: þ41 21 693 35 05.E-mail address: arata.nakajo@epfl.ch (A. Nakajo).Available online at www.sciencedirect.com journal h om epa ge: www.elsev ier.com/locate/he i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 9 2 6 9 e9 2 8 6

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Section: Introductionmentioning

confidence: 99%

Mechanical reliability and durability of SOFC stacks. Part II: Modelling of mechanical failures during ageing and cycling

Nakajo

Mueller

Brouwer

et al. 2012

International Journal of Hydrogen Energy

107

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“…7 [67]. Reactions do, however, become extremely critical during fuel cell operation, and cell ageing is therefore an extremely important aspect [83,[99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114]. Alkali-containing glass-ceramics are generally to be avoided due to the likelihood of pronounced glassceramic-metal reactions during cell operation.…”

Section: Sofc Alloysmentioning

confidence: 99%

Recent developments in the preparation, characterization and applications of glass- and glass–ceramic-to-metal seals and coatings

et al. 2011

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There has, in recent years, been a major revival of interest in glass-and glass-ceramic-to-metal seals and coatings for new applications. Experience dictates that many factors need to be taken into consideration in the successful design and manufacture of high-quality seals, particularly if an adequate component lifetime is to be achieved. For example, during their preparation, undesirable reactions may occur between diffusing metal species and glass constituents, and these can lead to the formation of highly localized internal stresses, which can initiate failure of a seal either during manufacture or, more seriously, whilst in service due to the influence of static fatigue. In the case of high-temperature systems, reactions under hostile operating conditions also need to be taken into consideration. In this review, the factors learnt from past experience that influence the formation and lifetime behaviour of glass and glass-ceramic/metal systems are briefly introduced, and their relevance to the newer applications including solid oxide fuel cell sealants and coatings on titanium for biomedical applications is discussed.

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“…The model derived from a model for glass-ceramics developed by Nguyen et al (2006) is termed "mechanistic" as its formulation uses both micromechanics and continuum damage mechanics. It assumes elastic MWCNTs completely randomly dispersed in a ceramic matrix whose cracking behavior is described by a continuum damage description.…”

Section: A Mechanistic Damage Model For Mwcnt Ceramic Compositesmentioning

confidence: 99%

“…Figure 5. Principle of the MBL Modeling Approach: (a) a crack inside a body subjected to remote loading, and (b) a damage process window containing a crack-tip and surrounded by a circular region where the asymptotic crack-tip fields are prescribed as boundary conditions (Nguyen et al 2006). …”

Section: Prediction Of Fracture Toughness For Mwcnt Reinforced Ceramicsmentioning

confidence: 99%

“…The critical damage stage represents the onset of crack propagation in the damage process window, and the corresponding value of K I at this stage defines the material Mode I fracture toughness, c I K . Crack propagation in the process window is captured by a vanishing element technique proposed by Nguyen et al (2006). Figure 6 presents the finite element mesh designed for the MBL analysis to predict fracture toughness of the MWCNT/3YSZ composite studied in this report.…”

Section: Prediction Of Fracture Toughness For Mwcnt Reinforced Ceramicsmentioning

confidence: 99%

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Fracture Toughness Prediction for MWCNT Reinforced Ceramics

Henager¹,

Nguyen²

2013

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SummaryThis report describes the development of a micromechanics model to predict fracture toughness of multiwall carbon nanotube (MWCNT) reinforced ceramic composites to guide future experimental work for this project. The modeling work described in this report includes (i) prediction of elastic properties, (ii) development of a mechanistic damage model accounting for matrix cracking to predict the composite nonlinear stress/strain response to tensile loading to failure, and (iii) application of this damage model in a modified boundary layer (MBL) analysis using ABAQUS to predict fracture toughness and crack resistance behavior (R-curves) for ceramic materials containing MWCNTs at various volume fractions.The modeling work provides insight and guidance to processing these materials for optimized composite microstructures to achieve the mechanical properties needed for high-temperature structural applications. The predictions show that homogeneously dispersed MWCNTs in a ceramic matrix significantly increase the resulting composite stiffness, strength, and fracture toughness. However, the fracture toughness increases may not attain the levels needed for the applications of these materials in advanced nuclear reactors. In addition, even assumingly well-distributed MWCNTs, the tensile strength and fracture toughness values saturate at moderate MWCNT volume fractions and tend to decrease at relatively high MWCNT volume fractions. Actually, the experimental difficulties to homogenously disperse MWCNTs throughout the matrix limit the MWCNT contents that can be achieved by mixing nanocrystalline SiC powders with MWCNTs and suggest that other processing methods and microstructural solutions need to be sought to better explore the load-carrying capacity of MWCNTs. In this report, predictions of fracture toughness as a function of MWCNT volume fraction have been validated against the experimental data for a MWCNT nanostructured zirconia composite determined by Mazaheri et al. (2011). The results of this report are valuable guidance to the experimental portion of this project and suggest that the development of additional toughening mechanisms needs to be explored in order to achieve the project goals of adequate fracture toughness for nuclear reactor structural applications.v Acronyms and Abbreviations

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Crack Growth in Solid Oxide Fuel Cell Materials: From Discrete to Continuum Damage Modeling

Cited by 50 publications

References 26 publications

Mechanical reliability and durability of SOFC stacks. Part II: Modelling of mechanical failures during ageing and cycling

Mechanical reliability and durability of SOFC stacks. Part II: Modelling of mechanical failures during ageing and cycling

Recent developments in the preparation, characterization and applications of glass- and glass–ceramic-to-metal seals and coatings

Fracture Toughness Prediction for MWCNT Reinforced Ceramics

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