Fracture of Ceramics

Robert Danzer, Tanja Lube, Peter Supancic, and Rajiv Damani 

Ceramic materials have a large fraction of ionic or covalent bonds, and this results in some special behavior - and, consequently, some special problems - with their reliable use in engineering. Within the temperature range of technical interest, dislocations are relatively immobile, and dislocation-induced plasticity is almost completely absent in ceramics l-3]. This is the basis for their extreme hardness and inherent brittleness, with typical values for the fracture toughness of ceramics ranging from 1 to lOMPa m, and the total fracture strain being commonly less than a few parts per thousand [4]. 

Mechanical testing is more complicated for ceramics than for ductile materials, since problems arising from any misalignment of specimens can become severe. They cannot be balanced by small amounts of plastic deformation, and this makes specimens with complicated shapes or the use of very sophisticated testing jigs necessary. In the case of hard and brittle ceramics, the machining of specimens is both expensive and time-consuming. 

The standardization of mechanical testing procedures began around 30 years ago at a national level. However, during the past ten years serious efforts on internationalization have also been made, and the first international standard (ISO 14704  

Ceramics Science and Technology Volume 2 Properties. Edited by Ralf Riedel and I-Wei Chen Copyright 2010 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-31156-9 

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Dynamic and Impact Fractures of Ceramic Composites at Elevated Temperature... 

K.-H. Yang, A. S. Kobayashi, and A. F. Emery, Effects of Loading Rates and Temperature on Dynamic Fracture of Ceramics and Ceramic Matrix Composites, in Ceramic Materials and Components for Engines, eds. V. J. Tennery and M. K. Ferber, American Ceramic Society, Columbus, OH, 1989, pp. 766-775. 

Approaches to characterizing the creep-fatigue fracture of ceramic composites. 

There is significant government, university, and industrial testing experience with nonstandard methods for determining fracture of ceramics and ceramic composites. For fiber-reinforced composites, this experience has been obtained predominantly at room temperature, although significant strides have been made in the past five years in elevated temperature testing. 

J. Swearengen, E. Beauchamp, R. Eagan, Proceedings of the Conference on Fracture of Ceramics, Pennsylvania State University, July 27-29, 1977. 

R. Danzer, T. Lube, P. Supancic, and R. Damani, Fracture of Ceramics, Advanced Engineering Materials, 10,275-298, (2008). 

Mecholsky [86] has proposed an equation of this sort to represent the brittle fracture of ceramics it would be of interest to investigate its applicability to the fracture of adhesive bonds. 

ANTHONY G. EVANS is the Gordon McKay Professor of Materials Engineering at Harvard University. His research interests include the mechanical properties of brittle materials particularly the fracture of ceramics under conditions of impact thermal and mechanical stress and failure prediction based on nondestructive evaluation. He is a recipient of the American Ceramic Society s Ross ColEn Purdy Award and has authored and co-authored several publications. Dr. Evans is a member of the National Materials Advisory Board and has served on several National Research Council committees. Dr. Evans was elected to the National Academy of Engineering in 1997 for his contributions to the development and understanding of structural materials. 

Holmer, P., and Nielsen, P. T. (1993), Fracture of ceramic femoral heads in total hip arthroplasty,/. Arthroplasty 8(6) 567-571. 

The fracture of ceramic components depends on many factors, including the chemistry and microstructure of the material and the resulting material s properties (e.g., toughness, J -curve behavior, etc.). The macroscopic appearance of fracture is, however, primarily influenced by the type of loading of the component and the resulting stress field. 

Such features are very common in brittle fracture of ceramic materials the fracture origin is a critical flaw which behaves like a crack the crack path is perpendicular to... 

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