Mode Conversion and Scattering of Lamb Waves at Delaminations in Composite Laminates

Pudipeddi, Gnana Teja; Ng, Ching‐Tai; Kotousov, Andrei

doi:10.1061/(asce)as.1943-5525.0001060

Cited by 30 publications

(27 citation statements)

References 54 publications

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“…These considerations can be employed for the characterization of delamination damage in SHM applications. In quasi-isotropic composite laminates, the fiber steering effects in the outermost plies have a significant influence on the scattering pattern [21,10], which is in agreement with the results presented in [16]. Whilst there are several numerical studies focused on A0 mode scattering at delaminations in composite laminates, limited experimental studies have been performed.…”

Section: Introductionsupporting

confidence: 85%

“…Due to increasing wave attenuation with frequency, especially for composite structures, the first antisymmetric (A0) and first symmetric (S0) modes at lower frequencies are often used for damage detection. Scattering and mode conversion at the damage location can be used for the detection and characterization of structural defects or material inhomogeneities [10]. Numerical simulations and experimental investigations have demonstrated the capacity for the detection of delaminations [11,12].…”

Section: Introductionmentioning

confidence: 99%

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Guided wave propagation and scattering at composite delaminations

Hervin

Fromme

2021

Health Monitoring of Structural and Biological Systems XV

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Composite structures, consisting of highly anisotropic layers of polymer matrix reinforced with high strength carbon fibers, are widely used for aerospace applications due to their low weight and high strength. However, impact during aircraft operation can lead to barely visible and difficult to detect damage. Depending on impact severity, delaminations can occur that reduce the structural integrity and load carrying capacity. Efficient structural health monitoring (SHM) of composite panels can be achieved using guided ultrasonic waves propagating along the structure. Guided ultrasonic wave propagation and scattering at circular delaminations was modelled using full three-dimensional (3D) Finite Element (FE) simulations in ABAQUS. Individual ply layers were modelled using unidirectional composite material properties to accurately capture the anisotropy effects. The guided ultrasonic wave propagation and scattered field at an artificial delamination was measured using a noncontact laser interferometer and quantified. Good agreement between experiments and Finite Element predictions was found and the energy trapping on top of a shallow delamination was verified. The influence of delamination shape and depth was investigated from a FE parameter study. The sensitivity of guided waves for the detection of delaminations due to barely visible impact damage (BVID) in composite panels has been verified.

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Section: Introductionsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Guided wave propagation and scattering at composite delaminations

Hervin

Fromme

2021

Health Monitoring of Structural and Biological Systems XV

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“…To overcome the drawbacks of traditional NDT methods, structural health monitoring (SHM) techniques were developed to assess integrity, reliability, and safety of structures in-time, in-situ, and continuously. 7,8 SHM techniques used for composite laminates include vibration-based, [9][10][11][12] optical fiber gratings, 8,13 guided-wave based techniques, [14][15][16][17] acoustic emission, 18,19 and impedance-based techniques. 20,21 Among them, vibration-based monitoring which uses changes in vibration parameters of the structure has a long history and it is regarded as one of the most important SHM techniques.…”

Section: Introductionmentioning

confidence: 99%

A comparison of machine learning algorithms for assessment of delamination in fiber-reinforced polymer composite beams

Wang

Ramakrishnan

et al. 2020

Structural Health Monitoring

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Structural health monitoring techniques based on vibration parameters have been used to assess the internal delamination damage of fiber-reinforced polymer composites. Recently, machine learning algorithms have been adopted to solve the inverse problem of predicting delamination parameters of the delamination from natural frequency shifts. In this article, a delamination detection methodology is proposed based on the changes in multiple modes of frequencies to assess the interface, location, and size of delamination in fiber-reinforced polymer composites. Three types of machine learning algorithms including back propagation neural network, extreme learning machine, and support vector machine algorithm were adopted as inverse algorithms for assessment of the delamination parameters, with a special focus on the interface prediction. A theoretical model of fiber-reinforced polymer beam with delamination under vibration was constructed to learn how the frequencies are affected by the delaminations (“forward problem”) and to generate a database of “frequency shifts versus delamination parameters” to be used in machine learning algorithms for delamination prediction (“inverse problem”). Multiple carbon/epoxy fiber-reinforced polymer beam specimens were manufactured and measured by a laser scanning Doppler vibrometer to extract the modal frequencies. Numerical and experimental verification results have shown that support vector machine has the best prediction performance among the three machine learning algorithms, with high prediction accuracy and only requiring a small number of samples. For predicting the interface of delamination which is a discrete variable, support vector machine classification has observed better prediction accuracy and requiring less running time than regression. This study is one of the first to prove the applicability of support vector machine for structural health monitoring of delamination damage in fiber-reinforced polymer composites and has the potential to improve the prediction capability of machine learning algorithms. Another significant outcome of the study is that the interface of delamination has been predicted accurately with support vector machine.

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“…17 The fundamental anti-symmetric ( A 0 ) and symmetric ( S 0 ) LW modes were proved to be highly sensitive to surface and internal cracking in plates. 18,19 They have been widely used to develop damage identification algorithms for assessing fatigue cracking, 20,21 delamination, 22,23 fiber breakage, 24 debonding, 25,26 cracks/notches, 27,28 and corrosion. 29 As a result, LWs have been commonly used as an essential tool to be implemented in SHM systems toward continuous monitoring of structures.…”

Section: Introductionmentioning

confidence: 99%

Understanding the interaction of the fundamental Lamb-wave modes with material discontinuity: finite element analysis and experimental validation

Fakih

Mustapha

Harb

et al. 2021

Structural Health Monitoring

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The interaction of guided waves with a material discontinuity is not well understood. This study investigates the propagation behavior of the fundamental Lamb-wave modes, the symmetric mode ( S0) and the anti-symmetric mode ( A0), upon interaction with welded joints of dissimilar materials. A plate with an intact AA6061-T6/AZ31B dissimilar joint was employed, and the interaction of the propagating wave with the material interface was scrutinized numerically and validated experimentally. Plane-wave approximation was also adopted to investigate the behavior of the symmetric modes, and its performance was compared to the numerical and experimental results. The effect of the angle of incidence on the reflection, transmission, and mode conversion of the incident modes was analyzed. The study was conducted as the excited Lamb wave propagated from AA6061-T6 to AZ31B (forward), and when the propagation direction was reversed (backward). Different techniques were developed to identify the in-plane and out-of-plane modes from the three-dimensional measurements and to separate wave reflections and transmissions of the joint. The fundamental shear-horizontal guided-wave mode ( SH0 mode) has evolved upon the interaction of the obliquely-incident Lamb-wave S0 mode with the interface. While the reflection of the SH0 mode from the joint was found to be well-pronounced, its transmission to the other material is extremely weak. The analytical solution, using plane-wave approximation, was accurate for predicting the behavior of the in-plane modes ( S0 and S0– SH0 modes). Despite the peaks appearing at the critical angle, the absolute values of the reflection coefficients of the studied modes have shown similar trends between the forward and the backward propagation directions. The total reflection of the excited wave, from the material interface, was not observed in any condition. The transmission coefficients of the S0 and A0 modes are almost constant until reaching very steep incidence angles [Formula: see text]. The results were experimentally validated on an intact AA6061-T6/AZ31B friction-stir-welded joint using an excitation frequency of 200 kHz. Measurements along the transmission and reflection directions were conducted using a three-dimensional scanning laser vibrometer. Experimental results showed very good agreement with both the analytical and the numerical ones.

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Mode Conversion and Scattering of Lamb Waves at Delaminations in Composite Laminates

Cited by 30 publications

References 54 publications

Guided wave propagation and scattering at composite delaminations

Guided wave propagation and scattering at composite delaminations

A comparison of machine learning algorithms for assessment of delamination in fiber-reinforced polymer composite beams

Understanding the interaction of the fundamental Lamb-wave modes with material discontinuity: finite element analysis and experimental validation

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