Non-destructive inspection of adhesively bonded patch repairs using Lamb waves

Pavlopoulou, S.; Soutis, Constantinos; Manson, G.

doi:10.1179/1743289810y.0000000030

Cited by 25 publications

(19 citation statements)

References 22 publications

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“…The effect of noise was tested which showed that OA can detect damage even in extremely noisy environments (SNR = 19). However, in the work by Pavlopoulou et al (2012a) OA exhibited a nonmonotonic behavior with the increasing damage which has been further studied and explained in the current work. For that purpose PCA was employed as a well-established technique, through which the drop in the Mahalanobis squared distance was explored even though the damage propagated.…”

Section: Linear Principal Component Analysis (Pca)mentioning

confidence: 78%

“…As previously investigated by Pavlopoulou et al (2012a) there are certain cases where the introduced damage to the structure is considerable enough to cause a significant signal time shift. This was demonstrated through an OA on an aluminum repaired panel that was subjected to fatigue loading and which identified unexpected behavior which is discussed and explained in the current work.…”

Section: Test Setsmentioning

confidence: 95%

“…OA proved to be the fastest technique, however, the assumption that the normal condition data follow a Gaussian distribution is not present in the other methods. Finally, Pavlopoulou et al (2012a) performed OA in order to detect crack propagation and the debonding of an external patch in an aluminum repaired structure, with significant success. However the Mahalanobis squared distance exhibited a slight drop in cases where damage kept increasing, a complication which will be further examined in this work.…”

Section: Pattern Recognition and Dimensional Reductionmentioning

confidence: 99%

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Novelty detection and dimension reduction via guided ultrasonic waves: Damage monitoring of scarf repairs in composite laminates

Pavlopoulou

Worden

Soutis

2015

Journal of Intelligent Material Systems and Structures

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This work focuses on structural health monitoring aspects of composite adhesively bonded repairs, evaluating their performance with guided ultrasonic waves. These repairs have shown remarkable potential in addressing repairability demands in new composite aircraft. More specifically, the behavior of a scarf repair under axial tensile loading was monitored with guided ultrasonic waves. The signal post-processing techniques focused on the extraction of the appropriate features, on the application of the pattern recognition and dimension reduction algorithms and on their subsequent correlation with the damage. A principal component analysis was employed that operated as a benchmark for the proposal of a more advanced data reduction method, the nonlinear principal component analysis. Appropriate damage indices were extracted and the results were correlated with images taken through a digital image correlation technique. The correlation of the extracted features with the early stage damage was performed and conclusions about the recovered strength through the scarf repair were deduced. The study focused on the selection of appropriate signal features and on their subsequent investigation through an outlier analysis. The limits of the applied outlier analysis were interpreted through principal component analysis and optimized through the concept of principal curves as derived through the nonlinear principal component analysis.

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Section: Linear Principal Component Analysis (Pca)mentioning

confidence: 78%

Section: Test Setsmentioning

confidence: 95%

Section: Pattern Recognition and Dimensional Reductionmentioning

confidence: 99%

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Novelty detection and dimension reduction via guided ultrasonic waves: Damage monitoring of scarf repairs in composite laminates

Pavlopoulou

Worden

Soutis

2015

Journal of Intelligent Material Systems and Structures

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“…Successful applications involve several engineering case studies based on high‐dimensional data sets . However, in complex structures that are subjected to extensive loading, novelty detection methods can potentially give false alarms .…”

Section: Lamb Waves Propagation For Damage Detectionmentioning

confidence: 99%

“…This can occur if the ultimate shear strain of the adhesive is exceeded under loading. Previous research on this subject has utilised novelty detection methods to detect damage when a metallic repaired structure was subjected to cycling loads .…”

Section: Introductionmentioning

confidence: 99%

Evaluation of instantaneous characteristics of guided ultrasonic waves for structural quality and health monitoring

Pavlopoulou

Staszewski

Soutis

2012

Struct. Control Health Monit.

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The analysis and extraction of the appropriate signal's features in structural health monitoring applications is one of the major challenges on which the robustness of the designed systems relies. Many strategies have been developed in the past, which utilise the identification of amplitude-based parameters for the evaluation of structural integrity. However, these parameters usually require a baseline reference, which might be extensively affected by noise, environmental or mounting conditions. This paper illustrates the applicability of Hilbert transform and Hilbert-Huang transform on the postprocessing of guided ultrasonic waves for evaluating the condition of relatively complex structural health monitoring applications. Two case studies are presented to demonstrate the suitability of the techniques, namely, the damage monitoring of an aluminium repaired panel and the cure level monitoring of symmetric carbon fibre-epoxy composite laminates. In the first case study, the technique exhibits sensitivity in propagation paths within damaged areas and shows good agreement with the developed damage, enabling the identification of critical areas. In the second study, the technique demonstrates a significant advantage over the traditionally adopted approaches and predicts accurately the cure level of the polymeric composite system. Inspection with guided ultrasonic waves is a wave-propagation-based method, which has lately attracted the attention of the scientific community, offering various industrial applications in monitoring pipes, pipelines and rails [7]. Guided waves propagate in a bounded media, which interacts with the boundaries of the structure and propagate through its thickness in two possible modes; symmetric (S n ) and antisymmetric (A n ). The mathematical equations that describe their behaviour are the same with bulky waves. The only difference is that, in the case of guided waves, the equations should satisfy the boundary conditions. The most widely used technique for health monitoring is inspection with Lamb waves. Lamb waves are elastic perturbations that occur in solid plates with free boundaries. Those perturbations are a combination of displacements that occur both in the direction of wave propagation and perpendicularly to the plane of the plate [8]. Lamb waves have been extensively used for health monitoring of advanced, complex structures. The scope of the current investigation concentrates on aspects of Lamb wave's application for health monitoring of two case studies, the first on damage monitoring of bonded patch repairs and the second on monitoring the cure process of a composite laminate.Adhesively bonded repair patches have lately received a considerable amount of interest for their potential repair applications for temporary (emergency or field) solutions to structural damage. In the aerospace industry, the interest in bonded patches emerges from the need to increase the operational life of ageing aircrafts. Such aircrafts are estimated to be approximately 30% of the worldwide fleet [9]....

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Inspection Methods

2018

Composite Structures

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Non-destructive inspection of adhesively bonded patch repairs using Lamb waves

Cited by 25 publications

References 22 publications

Novelty detection and dimension reduction via guided ultrasonic waves: Damage monitoring of scarf repairs in composite laminates

Novelty detection and dimension reduction via guided ultrasonic waves: Damage monitoring of scarf repairs in composite laminates

Evaluation of instantaneous characteristics of guided ultrasonic waves for structural quality and health monitoring

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