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Piezo-electricity is the ability of some materials to generate an electric charge in response to applied mechanical stress, and then induce a voltage. In some cases, the potential difference can reach thousands of volts. The electric lighters on gas stoves are a common example. Conversely, when an electric field is applied, stress and strain appear within it. Lead zirconate titanate, Pb(Zr,Ti)O3, generally called PZT, is one of the most commonly used materials in this family. Smart Material develops and manufactures composites using this fibre-shaped oxide.
(Published on October - November 2007 – JEC Magazine #36)
Piezo-ceramic PZT fibres
Piezo-ceramic PZT fibres are drawn using a textile spinning method which produces fibres with standard diameters of 105 μm, 250 μm and 800 μm and with typical lengths of 75 and 150 mm.
Piezo-composite materials using these fibres combine the valuable piezoelectric properties of ceramics with the robustness and conformability of plastics.
With the Macro Fibre Composites manufacturing technology, a NASA development, Smart Material possesses actuator know-how that has proved its suitability in aerospace applications and its versatility in many other applications. This technology makes it possible to assemble perfectly aligned fibre actuators that are no thicker than a few tenths of a millimetre. The actuators are contained in adaptive vibration control systems to eliminate unwanted vibrations in construction elements. This results in noise reduction, increased precision or higher loadbearing capacity. As the piezo effect is reversible, the fibre actuators can also simultaneously act as sensors or even harvest electrical energy from mechanical work. Applications range from vibration dampening in wings or car components to active forming of helicopter rotor blades, from exact positioning and stabilization of machine components to vibration damping in sports or household appliances, and from seismic disturbance measurements and health monitoring of buildings and aircraft to harvesting energy.
The so-called 1-3 fibre composites are prepared by epoxy infiltration of fibre bundles and dicing of the cube or cylinder-shaped blocks perpendicular to the direction of the fibres. The composite material shows superior ultrasound transduction properties due to its reduced acoustic impedance and high coupling factor.