Damage Detection of CFRP Stiffened Panels by Using Cross-Correlated Spatially Shifted Distributed Strain Sensors

Monica Ciminello,Antonio Concilio,Fulvio Romano,Bernardino Galasso,Natalino Daniele Boffa,Ernesto Monaco

doi:10.3390/app10082662

Monica Ciminello, Antonio Concilio + Show 4 more

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https://doi.org/10.3390/app10082662

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Abstract

This paper presents a cross-correlation function-based method applied to a spatially shifted differential strain readout vectors using distributed sensors under backscattering random noise and impact excitations. Structural damage is generated by low/medium energy impact on two aeronautical 24-ply CFRP (carbon fiber reinforced plastic) stiffened panels. Two different drop impact locations, two different sensor layouts and two different post-impact solicitations are provided for a skin-stringer debonding detection and length estimation. The differential signal with respect to an arbitrarily selected grounding is used. Then the effects of noise filtering are evaluated post-processing the differential signal by cross-correlating two strain vectors having one sensor gauge position lag. A Rayleigh backscattering sensing technology, with 5 mm of spatial resolution, is used to log the strain map. The results show a good coherence with respect to the NDI (nondestructive inspection) performed by ultrasonic C-scan (an ultrasonic imaging system) flaw detector.

Highlights

Structural damage investigation is of a primary importance for improving the safety levels and keeping operation costs under control
The paper proposes a damage identification method, based on a specific data processing provided provided by the application of the cross-correlation function to differential strain vectors having a by the application of the cross-correlation function to differential strain vectors having a spatial shift spatial shift lag
The fault zone is revealed with a max difference of 12.5%; it can be assumed that extrapolated data and actual measures (NDI) are in good agreement

Summary

Introduction

Structural damage investigation is of a primary importance for improving the safety levels and keeping operation costs under control. Maintenance processes are among the highest operative costs in the aircraft life. Safety is increasing its role more than ever since the continuous expansion of the flight market causes the current percentage protection levels should prevent increment of accident. The consolidated introduction of composite technologies in the commercial products, makes the structural monitoring valuable for future planes competitiveness. From this point of view, there are many open points, hard to be overcome by the current understanding of the engineering artefacts behavior.

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