Spatial integration of baseline-free damage detection algorithms based on dual-PZT for the structural health monitoring of anisotropic composite aeronautic structures

Abstract

The focus is put here on the Structural Health Monitoring (SHM) of composite aeronautic structure using Lamb waves emitted and recorded with piezoelectric transducers (PZT). Conventional algorithms perform Lamb waves acquisition in the healthy state of the structure (referred to as the “baseline”) and then compare incoming data from an unknown state with this one to detect, locate, classify and quantify any potential damage. The acquisition, storage, and update of the initially recorded baseline database constitute a severe drawback of such algorithms. Indeed, the structure under study as well as the environment may vary during its operational life without the appearance of any damage and thus the initial baseline may not be relevant at any instant where damage monitoring is needed. In order to circumvent this drawback, “baselinefree” method (such as the instantaneous baseline [BI] and rupture of reciprocity [RR]) have been developed. Moreover, the use of dual-PZT, i.e. concentric PZT made of a ring and a disk lying on the same ceramic, has been shown as attractive for baselinefree purposes. However, now that several algorithms based on dual-PZT are available, no study dealing with the spatial integration of the results provided by these algorithms have been reported in the literature. It is thus proposed in this paper to investigate strategies for the spatial integration of common baseline-free methods (namely BI and RR) on an experimental case of damage on a highly anisotropic composite plate. Results illustrate the decomposition of Lamb wave modes in signals measured via dual PZTs as well as the proposed spatial integration strategies for these methods.