Multi-damage imaging of composite structures under environmental and operational conditions using guided wave and Gaussian mixture model

Abstract

With the development of structural health monitoring (SHM), the demand for applying SHM technology to aerospace engineering applications has been greatly increasing over the last decades. However, aircraft are usually subject to complex environmental and operational conditions (EOCs) in service, making it a main obstacle of reliable damage evaluation under EOCs. Guided wave (GW) based imaging method has proved to be an effective SHM method in dealing with the multi-damage monitoring of aircraft composite structures. Although several methods are proposed, the EOCs problem is barely considered when monitoring multiple damages and needs to be addressed. Aiming at reliably locating multiple damages of aircraft composite structures under EOCs, this paper proposes a GW and Gaussian mixture model (GMM) based multi-damage imaging method. By adopting GMM to characterize the EOCs caused uncertainty on GW signals and measuring its variation during the monitoring process, an only sensitive to damage (OSD) feature parameter is first presented to recognize the subareas that there exist damages within the monitoring range. For each recognized damage subarea, the OSD feature signals of every GW pitch-catch path in this subarea are then constructed by GMM to combine with the delay-and-sum algorithm and to realize reliable damage imaging under EOCs. At last, a multi-damage imaging result can be generated, based on which the localization of multiple damages is achievable. Experiments on aircraft composite structure are carried out with the influence of changing temperatures, results show the effectiveness of the proposed method in multi-damage imaging and localization under temperature variation.