Estimation of the temperature field on a composite fan cowl using the static capacity of surface-mounted piezoceramic transducers

Abstract

The influence of temperature on SHM (Structural Health Monitoring) systems using guided waves is a major problem for their industrial deployment. One of the most used and cheapest SHM process developed in aeronautic context is based on piezoelectric transducers mounted on the monitored structure. Several methods are then used to assess the presence of damage. A popular one is based on tracking changes in the static capacity of the transducers: it is an efficient damage indicator in close area surrounding the device and is often used as a fault diagnosis of the transducer itself. However, monitoring decision are robustified with temperature sensors also mounted on the structure, adding wires and signal processing post-treatments. In this article, the static capacity is used to determine the temperature on each lead zirconate titanate transducer (PZT). By imparting this additional functionality to PZT devices, supplementary instrumentation is not necessary and an estimation of the entire temperature field of the structure is obtained. The original proposed approach is tested experimentally on a on a small composite plate and then on a large real part of an A380 composite nacelle. The results show that the temperature field on the structure can be estimated with a precision of ±5 °C using a linear regression between static capacity and temperature