Self-heat generation of embedded piezoceramic patches used for fabrication of smart materials

The use of smart materials, with embedded sensors and active actuators to provide real-time monitoring and controlling capabilities, has greatly increased in last decades. Piezoceramic flexible patches (PFPs) are particularly suitable for these applications due to their low thickness and intrusiveness. A critical point, when they are used as embedded actuators, is their self-heating, which can be a concern especially if structural materials with very low thermal conductivity such as plastic reinforced composites are considered. This paper aims to investigate such issue by examining three paradigmatic case studies: a) PFP in a “free” exposed to static air; b) PFP enclosed between two skins of polymeric material and c) PFP embedded into a glass fibre reinforced plastic (GFRP) composite panel. The main goal of the research has been to assess how the temperature, produced by self-heating of the piezo ceramic, is influenced by the surrounding material as the patch is enclosed or embedded into a structural element. A sensitivity analysis was performed to evaluate the effect on self-heating of either the amplitude or the frequency of the driven voltage. Moreover, a simple theoretical model, based on energies balance, has been derived in order to estimate the actual PFP temperature in both the b) and c) configurations.