SYNTHETIC ELEMENTS

Author: BUENO RODRIGUEZ JUAN SALVADOR.
Year: 2005.
University: AUTÓNOMA DE MADRID.
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: INSTITUTO DE CERAMICA Y VIDRIO. CSIC.

Summary: Ceramic materials have limited their use in structural applications by the lack of reliability associated with their behavior during the fragile fracture. An adequate design of sheet materials can lead to behavior higher than monolithic materials which constitute, in terms of the size of fault tolerance. In general, materials that present monolithic size of defect tolerance to show low levels of tension fracture. Therefore, the main objective of this thesis is the design and characterization of laminated ceramic materials that combine values stress fracture of the order of the materials of alumina and tolerance for defects. To do so, sheet materials are developed based alumina-titanato aluminum, given the wide variety of microstructures and mechanical responses of these compounds. To develop these materials laminated, it is necessary to determine the properties of the materials obtained in the same monolithic manufacturing conditions in order to establish the relationship between its mechanical behavior and the same material forming a layer. Materials are studied monolithic alumina-titanato aluminum with different contents of the second phase (10, 30 and 40% by volume), with controlled microstructure due to the use of two heat treatments limit (1450  ° C-2h and 1550  ° C-3h). Since at present there is no accepted standard methods for mechanical characterization of materials and monolithic ceramic composite laminates, part of the work is devoted to the study of methods appropriate characterization. It discusses the conditions for achieving stable fracture tests and quantify the various parameters of non-linear fracture; work of fracture (WOF), and fracture toughness (R curve JIC), along with the parameters to characterize materials linear: critical intensity tensions (KIC) and critical speed release of energy (GC). Depending on the values of these parameters and comments fractográficas, identifies reinforcing operational mechanisms in materials obtained. In the sheet materials obtained additional reinforcement is reached, laminated material itself due to synergistic effect of combining layers, which is revealed by the values of work of fracture. This increase is due to deflection and ramification of the crack microstructural level, which does not give rise to the deslaminación material at macroscópà ¬ ca. This increase is dependent on developments microstructural own laminated structure that occur during sintering materials or during cooling after sintering, and the reinforcement reached in these materials does not lose its effectiveness by increasing the working temperature.