Publication: Desarrollo y caracterización de nuevos materiales compuestos de matriz cerámica y refuerzo cerámico
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1999
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1999-01-26
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Abstract
En esta tesis se ha desarrollado un procedimiento de fabricación de materiales compuestos de matriz alúmina reforzados con circona en forma de partículas.
El procedimiento es simple y de bajo costo, ya que se compone de una fase de conformado por compresión uniaxial seguido de una fase de densificación mediante un sinterizado sin presión. Sin embargo, con él se ha conseguido fabricar materiales cuyas propiedades mecánicas pueden competir con las obtenidas con otros procedimientos más complejos y costosos.
Con este procedimiento se han obtenido probetas de alúmina monolítica de alta pureza, y probetas de alúmina reforzadas con un 15 y un 30% en peso de partículas de circona. Se ha analizado el comportamiento en flexión de los tres materiales fabricados, tanto en condiciones estáticas como dinámicas. Se ha comprobado que, al añadir una segunda fase en forma de partículas a la alúmina, se aumenta considerablemente la resistencia mecánica en flexión y, especialmente, la ductilidad del material resultante.
Se ha utilizado la distribución estadística de Weibull de dos parámetros para analizar la dispersión de los valores de las propiedades mecánicas medidas en los ensayos.
Utilizando técnicas de simulación aleatoria, se han determinado los mejores métodos de estimación, tanto de los parámetros de la distribución como de sus percentiles. Además, dado que los estimadores de las variables mencionadas son, a su vez, variables aleatorias, se ha realizado una caracterización estadística sistemática mediante funciones representativas de las mismas. Esta caracterización se resume en funciones de ajuste empíricas de los momentos y de los percentiles de dichas variables.
In this PhD thesis a manufacturing process for composite materials of alumina matrix reinforced with zirconia particles has been developed. The method is simple and economical, since it consists of a uniaxial compaction followed by a densification phase obtained by means of sintering without pressure. It however manufactures a material with mechanical properties similar to those obtained with more complex and costly procedures. Alumina reinforced with 15 and 30% in weight of zirconia particles and high purity monolithic alumina samples, have been obtained with this method. The static and dynamic bending behaviour of these three materials has been studied. The results showed that adding a second particle phase to the alumina considerably increases the flexure strength and, specially, the ductility of the new material. The two parameter Weibull distribution was used to study the scattering of the mechanical properties obtained from the tests. By means of random simulated techniques, the best estimation method for the parameters of the distribution as well as their percentiles, has been determined. Furthermore, as the estimators of the mentioned variables are, in tum, random variables, a systematic statistical characterisation of these has been performed. This characterisation is summarised in the empirical adjusted functions of the moments and the percentiles.
In this PhD thesis a manufacturing process for composite materials of alumina matrix reinforced with zirconia particles has been developed. The method is simple and economical, since it consists of a uniaxial compaction followed by a densification phase obtained by means of sintering without pressure. It however manufactures a material with mechanical properties similar to those obtained with more complex and costly procedures. Alumina reinforced with 15 and 30% in weight of zirconia particles and high purity monolithic alumina samples, have been obtained with this method. The static and dynamic bending behaviour of these three materials has been studied. The results showed that adding a second particle phase to the alumina considerably increases the flexure strength and, specially, the ductility of the new material. The two parameter Weibull distribution was used to study the scattering of the mechanical properties obtained from the tests. By means of random simulated techniques, the best estimation method for the parameters of the distribution as well as their percentiles, has been determined. Furthermore, as the estimators of the mentioned variables are, in tum, random variables, a systematic statistical characterisation of these has been performed. This characterisation is summarised in the empirical adjusted functions of the moments and the percentiles.