Structured Piezoelectric Composites: Materials and Applications

Structured Piezoelectric Composites: Materials and Applications

Van den Ende, D.A.

Van der Zwaag, S. (promotor)

Aerospace Engineering

Novel Aerospace Materials

2012-06-28

The piezoelectric effect, which causes a material to generate a voltage when it deforms, is very suitable for making integrated sensors, and (micro-) generators. However, conventional piezoelectric materials are either brittle ceramics or certain polymers with a low thermal stability, which limits their practical application to certain specific fields. Piezoelectric composites, which contain an active piezoelectric (ceramic) phase in a robust polymer matrix, can potentially have better properties both thermally and mechanically than the present single-phase piezomaterials, and yet exhibit sufficient piezoelectricity. The two main objectives of this thesis were to find new routes for manufacturing piezoelectric ceramic-polymer composites with adequate piezoelectric properties while retaining ease of manufacturing and explore new applications using these composites. It was found that a composite with piezoelectric particles dispersed in a high performance polymer matrix possessed improved thermomechanical properties such as thermal stability and temperature dependence of the output signal compared to conventional materials. The added flexibility of piezoelectric composites leads to a greater choice in device geometry and compatibility with polymer processing. Dielectrophoretic (electric field assisted) processing of piezocomposites results in increased permittivity and piezoelectric constants compared to conventional piezoelectric composites with randomly oriented particles, at little added processing complexity. A high degree of alignment could also be achieved using elongated piezoelectric particles, with a significant improvement in piezoelectric properties as a result. As an example, dielectrophoretically processed composites were used as energy harvesting materials in automobile tyres. Energy harvesting materials convert a small amount of energy from the environment to electricity, which can be used to power electronics such as wireless sensors. In automobile tyres, low frequency, high strains are present from which electricity can be generated using the piezoelectric effect. However, these high strains place stringent demands on the materials with respect to mechanical failure or depolarization, especially at elevated temperatures, so conventional piezomaterials are not robust enough to use. After testing inside automobile tyres the energy density of the piezoelectric ceramic-polymer composite materials is comparable to the reference materials and the output of the new piezoelectric ceramic-polymer composites did not degrade during operation. Therefore, these new materials open up new application fields for piezoelectric sensing and energy harvesting.

Piezoelectric
Composites
Dielectrophoresis
Connectivity
Electric field structuring
Sensors
Energy harvesting
Adhesion
Friction

http://resolver.tudelft.nl/uuid:77630992-2781-4c90-8bc5-964e685f5d72

9789461913463

Institutional Repository

doctoral thesis

(c) 2012 Van den Ende, D.A.