Publication: Caracterización de la respuesta piezoeléctrica de materiales compuestos basados en PVDF - BaTiO3
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2013
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2013-02-15
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Abstract
Gracias a sus características propiedades y sus múltiples aplicaciones, los materiales piezoeléctricos han ganado importancia en los últimos años. Un ejemplo de ello son los materiales compuestos de matriz polimérica y partículas cerámicas, como el formado por polifluoruro de vinilideno y titanato de bario. Ya que posee buenas propiedades mecánicas, piezoeléctricas y químicas, además de ser fácilmente procesables. En este proyecto se desarrollaron varios métodos de ensayo para caracterizar la respuesta eléctrica de compuestos basados en PVDF-BaTiO3. Este proceso incluyó desde idear y desarrollar el montaje de los ensayos elegidos, hasta la optimización de la geometría y configuración de las probetas de material compuesto; así como la toma de datos y su posterior análisis. Los experimentos que finalmente se utilizaron en la medida de la respuesta piezoeléctrica de los estudiados fueron dos; el primero consistió en lanzar una bola de acero de masa controlada y a una altura constante; y el segundo consistió en un motor oscilante que golpea a la muestra de forma periódica con una fuerza constante. Una vez desarrollado dos métodos de ensayo, se estudió la respuesta piezoeléctrica en función de la cantidad de partículas de material cerámico embebidas en la matriz polimérica. Para ello se utilizaron las medidas realizadas a través del experimento de la bola vertical y del experimento del motor. Por medio del primer ensayo se pudo observar que: (i) a medida que aumenta la cantidad de cerámico en la muestra los valores picos de voltaje medidos aumentan, pero esta relación creciente se ve truncada en el caso del 10%. Dado que en valores tan altos de material cerámico su respuesta piezoeléctrica, que es opuesta a la del polímero, es significativa frente al del PVDF; (ii) respecto al tiempo de amortiguamiento, se puede ver una tendencia creciente del parámetro. En el caso del ensayo del motor se obtuvieron las siguientes conclusiones: (i) cuanto mayor es la cantidad de refuerzo cerámico, la respuesta se vuelve más atenuada en cuanto a valores pico, este comportamiento se atribuye, como se ha comentado anteriormente por el aumento de la influencia del efecto piezoeléctrico del titanato de bario frente al del PVDF, efecto que también se da en el experimento de la bola vertical, aunque en este caso el efecto aparece antes pudiéndose atribuir a la no liberación de la energía elástica de la probeta; (ii) El material responde de manera periódica y con una forma similar al anterior experimento. _____________________________________________________________________________________________________________________________
Thanks to their specific properties and their multiple applications, the piezoelectric materials have grown in importance among the last years. An example of those materials is the nanocomposites such as those studied in this work, which consist in ceramic particles embedded in polymer matrix. In particular poly (vinylidene) fluoride and barium titanate nanoparticles were used due to their good mechanical, chemical and piezoelectric properties, plus the easily way to being process. In this project, several different tests were developed in order to define the electric response of the PVDF-BaTiO3 composite materials. This process included the design and development of the different experimental set-ups, the optimization of the geometry and the configuration of the composite specimens as well as the subsequent data acquisition and processing. Two experiments were used in to measure the piezoelectric response of the materials; the first one consisted in throwing a steel ball with a known mass and in a constant height; and the second one consisted in an oscillating engine that hits the specimens with a constant periodic force. Once the two different tests have been developed, the piezoelectric behaviour was studied based on the amount of the ceramic particles dispersed in polymer matrix. Two different approaches were used, the steel ball experiment and the one of the oscillating engine. In relation to the first approach it was observed that by the first one has been observed: (i) the more quantity of ceramic particles there were specimens the lower the maximum and minimum values of the voltage were observed. This result may be attributed to the fact that the mechanic properties that has the specimen are improved. But this relation is broken in the test tubes with 10% mainly due to the fact that the BaTiO3 piezoelectric response becomes more significant, and this response is opposite of the PVDF one; (ii) the damping time increases as the amount of BaTiO3 does. The results obtained with the oscillating engine showed that: (i) the larger the amount of BaTiO3 the weaker the electric signal it becomes. This behaviour may be explained, by the fact that the influence of the BaTiO3 piezoelectric effect becomes more significant than that of the PVDF. However, in this case the effect appears before probably due to the fact that the elastic energy is not totally released; (ii) the material responses has a periodic response with the same morphology than that obtained for the steel ball approach.
Thanks to their specific properties and their multiple applications, the piezoelectric materials have grown in importance among the last years. An example of those materials is the nanocomposites such as those studied in this work, which consist in ceramic particles embedded in polymer matrix. In particular poly (vinylidene) fluoride and barium titanate nanoparticles were used due to their good mechanical, chemical and piezoelectric properties, plus the easily way to being process. In this project, several different tests were developed in order to define the electric response of the PVDF-BaTiO3 composite materials. This process included the design and development of the different experimental set-ups, the optimization of the geometry and the configuration of the composite specimens as well as the subsequent data acquisition and processing. Two experiments were used in to measure the piezoelectric response of the materials; the first one consisted in throwing a steel ball with a known mass and in a constant height; and the second one consisted in an oscillating engine that hits the specimens with a constant periodic force. Once the two different tests have been developed, the piezoelectric behaviour was studied based on the amount of the ceramic particles dispersed in polymer matrix. Two different approaches were used, the steel ball experiment and the one of the oscillating engine. In relation to the first approach it was observed that by the first one has been observed: (i) the more quantity of ceramic particles there were specimens the lower the maximum and minimum values of the voltage were observed. This result may be attributed to the fact that the mechanic properties that has the specimen are improved. But this relation is broken in the test tubes with 10% mainly due to the fact that the BaTiO3 piezoelectric response becomes more significant, and this response is opposite of the PVDF one; (ii) the damping time increases as the amount of BaTiO3 does. The results obtained with the oscillating engine showed that: (i) the larger the amount of BaTiO3 the weaker the electric signal it becomes. This behaviour may be explained, by the fact that the influence of the BaTiO3 piezoelectric effect becomes more significant than that of the PVDF. However, in this case the effect appears before probably due to the fact that the elastic energy is not totally released; (ii) the material responses has a periodic response with the same morphology than that obtained for the steel ball approach.
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Materiales compuestos, Materiales piezoeléctricos