Assessment of viscoelastic crack bridging toughening in refractory materials

Viscoelastic bridges can be formed in refractory ceramics while cooling from high temperatures. Such bridges can shield crack tips, thus reducing the effective crack tip stress intensity factors leading to higher resistance to creep and thermal shock. The extent to which the crack tip stress intensi...

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Bibliographic Details
Published in:Journal of the European Ceramic Society 2008, Vol.28 (10), p.1941-1951
Main Authors: Boccaccini, D.N., Cannio, M., Volkov-Husoviæ, T.D., Dlouhy, I., Romagnoli, M., Veronesi, P., Leonelli, C.
Format: Article
Language:English
Subjects:
Applied sciences
Building materials. Ceramics. Glasses
Chemical industry and chemicals
Cordierite–mullite
Exact sciences and technology
Fracture mechanics
Fracture toughness
Image analysis
Refractory products
Silica-alumina refractories
Viscoelastic toughening
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Summary:Viscoelastic bridges can be formed in refractory ceramics while cooling from high temperatures. Such bridges can shield crack tips, thus reducing the effective crack tip stress intensity factors leading to higher resistance to creep and thermal shock. The extent to which the crack tip stress intensity is reduced can be estimated from fracture mechanics models that include experimental measurement of crack bridging and microstructural parameters. In this paper a novel approach is proposed for the assessment of the effective crack bridging toughening from combining destructive and non-destructive test methods. Fracture toughness values were determined applying chevron notched specimen technique and surface damage of the specimen was monitored by image analysis. Different cordierite–mullite compositions characterized by different microstructure morphologies and crack propagation behaviour were investigated. A brief discussion about the correlation between thermo-mechanical properties, microstructure, crack propagation behaviour and thermal shock resistance is presented. Moreover, an empirical model able to determine the presence and effectiveness of the viscoelastic crack bridging ligaments acting in the microstructure under thermal shock conditions and their degradation with increasing thermal shock cycles from parameters measured at room temperature is presented.
ISSN:0955-2219
1873-619X
DOI:10.1016/j.jeurceramsoc.2008.01.021