IMPACT DAMAGES LOCALIZATION IN COMPOSITE LAMINATES USING WAVELET DISCRETIZATION METHOD - Scientific conference
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Рік заснування видання - 2011

IMPACT DAMAGES LOCALIZATION IN COMPOSITE LAMINATES USING WAVELET DISCRETIZATION METHOD

11.11.2025 10:02

[3. Technical sciences]

Author: Alexander Pysarenko, associate professor, PhD, Odessa State Academy of Civil Engineering and Architecture



The application of advanced non-destructive testing techniques is paramount for ensuring the structural integrity of composite laminates, which are widely utilized across aerospace, automotive, and civil engineering sectors due to their superior strength-to-weight ratio. Among the critical threats to these materials is low-velocity impact, which can induce internal delamination and matrix cracking, often invisible on the surface, significantly degrading the structure's mechanical properties and residual strength. The localization and accurate sizing of such impact-induced damage are crucial for timely repair and maintenance decisions. A large number of studies focus on the utility of the wavelet discretization method, particularly leveraging wavelet transform (WT) analysis, for enhanced damage detection and localization within these laminated composite structures [1].

Wavelet analysis represents a powerful mathematical framework for analyzing transient signals, such as those generated by stress waves propagating through a material, making it highly suitable for structural health monitoring applications. Unlike the traditional Fourier transform, which provides frequency information averaged over the entire duration of a signal, the WT offers a time-frequency localization capability. This means it can simultaneously reveal both the frequency content of a signal and its precise location in time, or, by extension in structural wave propagation analysis, in space. This dual localization is achieved through the use of a mother wavelet function, which is scaled (to capture different frequencies) and translated (to capture different time/spatial locations). The result is a series of coefficients that represent the signal's similarity to the mother wavelet at various scales and positions.

In the context of laminated composites, impact events generate complex stress waves as Lamb waves, Rayleigh waves, and bulk waves that travel through the material [2]. When these waves encounter a discontinuity, such as a delamination or a crack, they are scattered, reflected, and attenuated. These interactions introduce distinct anomalies or abrupt changes in the propagating wave signal. The key advantage of the WT is its exceptional ability to detect and isolate these transient, high-frequency disturbances or singularities that mark the presence of damage.

The wavelet discretization method, often employed in conjunction with signal processing of guided waves, capitalizes on the localized nature of the WT. By applying a continuous or discrete wavelet transform to the sensor signals (e.g., from piezoelectric transducers) collected from the composite structure, researchers can effectively decompose the raw, often noisy, wave data. Damage localization is then achieved by observing the sudden changes or peaks in the wavelet coefficients. These peaks correspond spatially to the boundaries or locations of the internal damage. For instance, a delamination acts as a local stress concentrator and wave guide discontinuity; as the interrogating wave passes over it, the local stiffness changes, causing a measurable alteration in the wave's phase velocity and amplitude. The sharp gradients introduced by these alterations are highly concentrated in specific wavelet scales, allowing for precise pinpointing.

Different wavelet families, such as Daubechies, Morlet, Coiflets or Symlets, are chosen based on the specific type of signal and the nature of the damage being investigated. The selection of the appropriate mother wavelet is critical, as its shape and characteristics should optimally match the singularity or feature introduced by the damage. For example, wavelets with a higher number of vanishing moments are often better at characterizing sharp discontinuities. Moreover, the choice of decomposition level or scale plays a crucial role; lower scales capture high-frequency details pertinent to small, localized damage, while higher scales provide information about overall structural behavior or larger damage features.

The application of wavelet analysis for damage detection in laminated composites has proven superior to techniques relying solely on time-domain or frequency-domain analysis alone. It offers robust noise filtering capabilities, simultaneously processing signals for temporal and spectral characteristics. In practical implementations, a baseline signal from the undamaged structure is often compared against the signal from the potentially damaged structure. The difference signal is then subjected to wavelet analysis. The magnitude and spatial distribution of the resulting wavelet coefficients in the difference signal directly map the location, and sometimes provide insight into the extent, of the impact damage. 

This study developed an impact localization scheme based on the arrival time of acoustic wave propagation data in laminated composite materials. Numerical modeling was conducted for various wave types with different velocities and dispersion characteristics. The wavelet discretization methodology was performed based on the analysis of both the kinematic characteristics of the anti-symmetric Lamb wave mode and the decomposition of the Db3 wavelet transform results. The spectrum of numerical values for the group velocity was obtained using Continuous Wavelet Transform (CWT) time-frequency analysis for composite laminates. The set of calculated positions for the impact deformation zones coincides with good accuracy with the results from experimental investigations into the localization of defects in laminated structures.

References:

1. Jeong, H., & Jang, Y. S. (2000). Wavelet analysis of plate wave propagation in composite laminates. Composite Structures, 49(4), 443-450. https://doi.org/ 10.1016/S0263-8223(00)00079-9

2. Pant, S., Laliberte, J., Martinez, M., Rocha, B., & Ancrum, D. (2015). Effects of composite lamina properties on fundamental Lamb wave mode dispersion characteristics. Composite Structures, 124, 236-252. https://doi.org/ 10.1016/j.compstruct.2015.01.017



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