| Τύπος: |
Διάλεξη |
| Ημ/νία Έναρξης: |
5/11/2009 |
| Ημ/νία Λήξης: |
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| Ώρα Έναρξης: |
13:00 |
| Ώρα Λήξης: |
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| Ομιλητής: |
Δρ. Θεοχάρης Μπαξεβάνης, Συμβασιούχος Λέκτορας, Τμήμα Εφαρμοσμένων Μαθηματικών, Πανεπιστήμιο Κρήτης |
| Τίτλος: |
Creep-enhanced damage of continuous fiber-reinforced ceramic matrix composites |
| Περιγραφή: |
Ceramic matrix composites (CMCs) combine reinforcing ceramic phases with a ceramic matrix to create materials with new and superior properties that can be used as structural parts in high-temperature environments. It is now well established that the time-dependent deformation of CMCs is not only the result of diffusional and cavitational creep of the constituents (in the range of operational temperatures usually both the fibers and the matrix creep) but is strongly affected by the strength degradation and evolution of constituents damage as well as by the mechanical properties of the interface. Here, we present a micromechanically based analysis of composite damage and subsequent failure in creep-rupture conditions which is inherently statistical, and incorporates stochastic analysis of fiber-strength degradation in accordance with weakest-link statistics, effects of fiber pull-out and the fully-saturated matrix crack-damage state, under the well established global load sharing assumption. The influence of interface shear creep on the composite creep behaviour is modelled on the basis of a shear-lag stress analysis methodology. Overall, the resulting model is capable of describing interrelated phenomena that are observed experimentally such as the primary creep regime, the tertiary creep regime and the lifetime (of a material system Nextel 610/alumina-yttria at temperatures of $950^o$ and $1050^oC$); thus the model can capture the key damage evolution and its time dependence. The sensitivity of the overall mechanical performance to the individual material parameters is discussed. The results obtained are of importance for effective composite design and application in structural components. |
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