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Fracture Behaviour of Inherently Brittle Materials
Dlouhý, Ivo
The proceedings of workshop on Fracture Behaviour of Inherently Brittle Materials organised within series Brittle Fracture. The support of Czech Science Foundation, project Nr 101/02/0683, and Grant Agency of the Academy of Sciences of the Czech Republic, project Nr. A2041003, is gratefully acknowledged.
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Fracture toughness and fracture micromechanisms in fibre reinforced brittle matrix composites
Dlouhý, Ivo ; Chlup, Zdeněk ; Boccaccini, A. R.
Fracture toughness and fracture micromechanisms in fibre reinforced brittle matrix composites. For monolithic ceramics, the fracture toughness determination using a specimen with straight and/or chevron notch in the three (four) point bend test for monolithic ceramic materials can be taken as standard techniques. In case of composite materials, mainly of brittle matrix reinforced by fibres the crack growth resistance increases as the crack propagates. In addition, the long fibres stimulate delaminations along their interfaces with the matrix perpendicularly to the major crack. Fracture toughness determination in cases when delaminations take place is difficult. The chevron notch technique appears to be the only technique that enable to obtain exact fracture toughness characteristics by its natural ability to "keep" the mode I major crack propagation. Based on fractographic analyses and comparisons of data from chevron and straight notch technique the corresponding evidences are supplied.
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Influence of sample geometry (size) effect on fracture toughness characteristics of brittle materials
Chlup, Zdeněk ; Dlouhý, Ivo
Influence of sample geometry (size) on fracture toughness characteristics of brittle materials. The fracture toughness is an important characteristic for structures design even more when inherently brittle material is used. Ceramics materials are those ones where knowledge of exact fracture resistance is crucial and frequently lack of this knowledge can disqualify such material for application in a given component. Over last few years a big effort was paid in investigation in this field. Recently a standardized methodology for fracture toughness evaluation was introduced. However there are many restrictions, mostly in geometrical requirements, and often it is difficult to reach them especially when new material is developed. Data obtained from different geometries of specimen and/or loading conditions time to time it is necessary to compare. The paper attempts to reveal questionable points when data from various sources are compared.
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