Heat generation of a piezoceramic induced-strain actuator embedded in a glass/epoxy composite panel

The thermal response of a specific piezoceramic induced-strain actuator (the Penn State SPICES 'frame' actuator) was investigated under two conditions: (1) as a free device; and (2) embedded in a woven glass/epoxy composite panel. Actuators were driven at various combinations of electric field strengths and frequencies. Field strengths ranged from 75 kV/m to 1.5 MV/m (10 to 200 Vrms over a 135 micron thickness), while frequencies ranged from 100 Hz to 2000 Hz. The 50-ply composite panel was instrumented with thermocouples at 4 locations through the panel thickness. Temperature measurements were recorded continuously from an initial ambient isothermal state until a steady state temperature distribution was reached. Temperatures increased with frequency and field level, with heat generation roughly proportional to the frequency and to the square of the field level, consistent with a dielectric loss mechanism. The temperature rise at the actuator-composite interface, when driven at 100 Vrms and 500 Hz, was 50 degrees Celsius. The data indicate that self-heating in applications involving a combination of high field levels, high frequencies, and thick composites can result in high internal temperatures, and possibly lead to reduced performance and reliability.