Flexible Piezoelectric Actuators

Langley Research Center,

Flexible, compact, hermetically sealed piezoceramic actuators with robust electrical leads have been developed for use in actively controlling aerostructures to suppress noise, vibration, and flutter on experimental aircraft. An actuator of this type, denoted a Flex Patch, is meant to be placed in a strategic location to oppose a predominant mode of vibration in a given structure.

A Flex Patch Is Very Flexible, even though it contains a piezoceramic wafer that, taken by itself, would be extremely brittle and could not be bent as much as shown here.

A Flex Patch is a composite structure that includes a lead zirconate titanate (PZT) wafer and nickel ribbon leads sandwiched between thermoplastic layers. During fabrication, the structure is held together with Kapton (or equivalent) polyimide tape and placed in an autoclave for processing through a prescribed temperature-and-pressure cycle.

The most remarkable attribute of a Flex Patch is its flexibility (see figure) and its ability to perform as well while bent as it does when undeformed. Taken by itself, the piezoceramic wafer that goes into a flex patch is extremely brittle and is broken when deformed even slightly. The flexibility of the Flex Patch greatly exceeds that of the piezoceramic wafer that it contains. The unique flexibility makes it possible to attach a Flex Patch to a highly curved surface. This characteristic also makes it possible to embed a Flex Patch into a composite-material structure of any of a variety of shapes.

Another benefit of the Flex Patch is the strength of electrical-lead attachments, which have been sources of failure in the past because of the difficulties associated with the soldering of leads to a PZT. These leads stay connected firmly in place and form a monolith along with Flex Patch composite, providing an electrically insulated package. The leads and the PZT stay hermetically sealed — an advantage for use in adverse environments. Flat, flexible, male clincher connectors (similar to those found within computers) are crimped onto the ends of the ribbon leads to finish the package.

Thus far, Flex Patches have been operated at low voltages. After a Flex Patch has been subjected to a high-voltage poling process, the common operating potential is 200 V, although the Flex Patch could also function when connected to a standard 110-V, 60-Hz household outlet.

In addition to working well as an actuator, a Flex Patch can also generate an electrical response to a mechanical input. This characteristic makes it possible to use a Flex Patch as a sensor.

This work was done by Garnett Horner, John Teter, and Eugene Robbins of Langley Research Center.

This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to