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Non-elastic behaviours of high-porosity ceramics and ceramic-polymer composites

Yuriy M. Podrezov 1S O. Firstov 1M Szafran 2Krzysztof J. Kurzydlowski 2

1. Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Krzizanovsky, Kyiv 38(044), Ukraine
2. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland


High porosity ceramics and ceramic-polymer composites are now widely applied in a number of fields and in particular in medicine. The present paper is focused on mechanical properties of these materials and possible ways for their improvement. One of them is via increasing relative stiffness. The other is by rising the fracture toughness and deformation energy, which can be achieved by increasing the volume fraction of pores due to non-elastic behaviours of high porosity ceramics under bending. The third method is to increase absorbing capacity of strain energy. In the paper the sensitivity of these three effects to the microstructure of pores and solid phase is analysed and methods for microstructure optimisation are proposed.
Fracture mechanisms of porous ceramics transform with increasing porosity from a brittle cleavage typical of monolithic materials to cracking of separated defects in high-porosity ones. According to the model proposed, four stages of process can be identified: (a) loading without micro-cracking, (b) stable, non-localised micro-cracking before reaching the stress maximum, (c) stable localised microcracking after stress maximum point and (d) unstable (catastrophic) fracture. These stages results in non-linear behaviour of high porosity ceramics under bending and compression making these materials attractive for in terms of damping capacity.
The proposed model of fracture can be used to determine the dependence of the number of cracks per unit area on the level of applied stresses. The important conclusion, that can be derived from this model is that properties of the high porosity ceramics can be improved by infiltrating them with polymers due to relaxation of stress concentrations.


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Presentation: oral at E-MRS Fall Meeting 2003, Symposium E, by Yuriy M. Podrezov
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-08 15:51
Revised:   2009-06-08 12:55