Development of Laboratory-scale Lamb Wave-based Health Monitoring System for Laminated Composites (original) (raw)
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Structural health monitoring in composite materials using Lamb wave methods
2002
Cost-effective and reliable damage detection is critical for the utilization of composite materials. This paper presents part of an experimental and analytical survey of candidate m ethods for in-situ damage detection of composite materials. Experimental results are presented for the application of Lamb wave techniques to quasi-isotropic graphite/epoxy thin coupons and sandwich beams containing representative damage modes, including delamination, transverse ply cracks and through-holes. Optimization experiments provided a procedure capable of easily and accurately determining the presence of damage by monitoring the transmitted waves with piezoceramic sensors (PZT). Lamb wave techniques have been proven to provide more information about damage type, severity and location than previously tested methods, and may prove suitable for structural health monitoring applications since they travel long distances and can be applied with conformable piezoelectric actuators and sensors that require little power.
2022
The most common researched area of damage in a composite material such as carbon fibre reinforced plastics (CFRP) used currently in aircraft construction is barely visible impact damage (BVID), significantly reducing mechanical properties. Early detection and qualification would improve safety and reduce the cost of repair. In this context, structural health monitoring (SHM) techniques have been developed that could monitor a structure at any time by using a network of sensors. Widely used discrete ceramic transducers can generate and sense Lamb waves travelling in the structure. Wave propagation must then be analysed for effective damage identification. An effective SHM system is desired to meet several demands, such as minimised weight penalty, non-intrusive system not interfering with the structure performance, costeffectiveness for implementation with targeted sensitivity and area coverage, capability of monitoring non-accessible and critical hot spot regions, robustness, and reliability. This review starts with an introduction on Lamb waves fundamentals and their use in SHM, and then particularly focuses on methods using piezoelectric transducers and mode selection. Some relevant applications on different structural configurations are discussed. Finally, recent developments on piezoelectric coating and direct-write sensor technology for tailored transducers are highlighted with some thoughts for near future research work.
Long range damage assessment through Lamb waves in large plate-like composite structures
Journal of Advanced Science, 2000
The health of a structure depends on both the homogeneously distributed degradation of its mechanical properties during its life cycle and the presence of localised defects such as cracks or delaminations. The proposed non-destructive health monitoring method allows recovering both kinds of information using ultrasonic waves. To avoid traditional techniques limitations, such as coupling reproducibility for instance, we propose here to integrate a piezoelectric element into the plate-like composite structure. The element dimensions are determined in order to uncouple the frequency ranges of the thickness and radial vibration modes. The thickness mode is used to monitor the homogeneous ageing of the structure through electrical impedance measurement. As for the radial vibrations, they are used to generate and detect Lamb waves, which have the advantage of propagating over long distances and offering specific sensitivity of various modes to different kinds of defects. The present work focuses on this last application and studies the ability of the proposed technique to detect and identify defects such as low speed impact-induced delaminations and cracks in composite plate-like structures.
Lamb Wave Based Damage Detection in Composite Panel
Journal of the Indian Institute of Science, 2013
This paper presents a Lamb wave based methodology for damage detection using frequency spectra in thin metallic and composite plates and a more realistic structure like stiffened carbon-epoxy composite panel. The stiffened specimen considered encompasses almost all the complexities that may be encountered while implementing a Lamb wave based Structural Health Monitoring (SHM) system for real time applications. The complexities considered include cluttering of wave modes, reflections from the stiffeners and edges, effect of structural in-homogeneity like variable thickness on time of flight and amplitude. Thin Piezoelectric patches operating in d31 modes are used as transducers for Lamb wave generation in pitch catch configuration and excitation of A0 mode through mode tuning. A Root Mean Square Deviation Damage Index (RMSD DI) based frequency spectra is derived out of the windowed A0 mode of the Lamb wave response. The efficiency of the DI to predict damage severity is tested experi...
Structural Health Monitoring System Using Piezoelectric Networks with Tuned Lamb Waves
Shock and Vibration, 2010
The paper presents a structural health monitoring system based on propagation of tuned Lamb waves and their interference with discontinuities. The dispersion curves are studied to determine the appropriate type and dimension of transducers and to select the optimum scanning frequencies and relevant propagation modes. A piezoelectric sensor network was implemented in an aluminum plate in order to generate and to sense the wave propagation and associated reflections. The algorithm developed for damage detection relies on the comparison of undamaged and damaged responses of the structure. Combinations of filters and statistical methods were applied to detect differences in the sensor signals acquired for the two different states (damaged and undamaged), corresponding to damage reflections. In order to eliminate the false positives due to noise, a probability analysis is performed to obtain the final damage position. The software designed for the current application allows the automatic calculation of dispersion curves, it executes the scans, performs data processing, executes the detection algorithm and presents the probable damages and their positions in a graphical form. Experiments were performed with the introduction of cumulative damages in the plate such as surface and through-the-thickness holes and cuts, ranging from 7 mm to 1 mm in diameter. Additionally, a stringer was attached to the plate by a single rivet line to simulate an aircraft skin structure. Cuts originating from rivet holes and connecting adjacent rivets, as well as loosened rivets were detected by the system. The introduction of the stringer resulted in a loss of precision in the determination of the radial position of the damages near it. Also, the network revealed significant difficulties in the detection of damages beyond the stringer.
Damage Detection in Stiffened Composite Panels Using Lamb Wave
2012
This paper presents a Lamb wave based methodology for damage detection in stiffened carbon-epoxy composite panel with stiffener de-bonding. The specimen considered encompasses most of the complexities that may be encountered in implementing a real-life Lamb wave based structural health monitoring (SHM) system. These complexities include multiple reflections from the stiffeners and edges, cluttering of wave modes, effect of variable thickness on time of flight and amplitude. Piezoelectric patches are used as transducers and only A0 mode is excited through mode tuning. A damage index (DI) based on root mean square deviation (RMSD) is derived from the frequency spectra of the windowed A0 mode of the Lamb wave response. The efficacy of the DI for predicting the presence of damage is tested experimentally for a specimen with known location of damage. In addition, a 2-D finite element (FE) simulation is carried out to validate the experimental results.
Optimization of Lamb wave methods for damage detection in composite materials
2001
Cost-effective and reliable damage detection is critical for the utilization of composite materials. This paper presents part of an experimental and analytical survey of candidate methods for in-situ damage detection of composite materials. Results are presented for the optimization of Lamb wave techniques applied to quasi-isotropic graphite/epoxy specimens containing representative damage modes. Linear wave scans were performed on narrow laminated coupons and sandwich beams by monitoring the transmitted waves with piezoceramic sensors (PZT). Optimal actuator and sensor configurations were devised through experimentation, and various types of driving signals were explored. Lamb wave t echniques have been proven to provide more information about the presence of damage and its severity than previously tested methods, and may prove suitable for structural health monitoring applications since they travel long distances and can be applied with conformable piezoelectric actuators and sensors that require little power.
Structural Health Monitoring of Lightweight Structures by Use of Lamb Waves
In the experimental part of this work, the excitation and propagation of Lamb waves in carbon fiber reinforced composite plates is presented by visualized experimental data. Lamb waves are easily excited by thin piezoelectric patches adhered to the surface of the structure. Their propagation is observed experimentally by Scanning Laser Vibrometry. Results from Lamb wave reflection and mode conversion at damage locations are shown indicating the potential and the restrictions of the inspection method. In the numerical part of this work, honeycomb sandwich panels are considered which are also frequently used as lightweight structures due to their high stiffness. Because of their complex build-up the understanding of Lamb wave generation and propagation is much more difficult than in the case of conventional composite plates. Therefore, finite element simulations have been performed to study guided waves at different frequency ranges and in sandwich panels with different build-ups. The...
Lamb Waves for Detection of Delamination in Composite Plates
In this paper, a configuration for finding delamination in carbon-based plate like structureis presented and reviewed. Using induced guided Lamb Wave in order to identify damages in a carbon plate by analyzing key distinct features and using support vector machine (SVM) tools to compare data from a delaminated plate and reference training data. This research resets a sensor circle configuration for identifying and scanning delamination in a panel by using the wavelet transform to create a descriptive feature extraction method, then using the known sensor position to create a reliable and robust C-scan. This method enables both post-production and ongoing monitoring of plate-like carbon-based composite structures. In the form of a low-cost scan option that can detect even sub-surface delamination.
2014
Carbon Fiber Reinforced Polymer composites have been developed since the ’60s and allow the design of resistant and innovative lightweight primary structures, replacing traditional metallic materials. However, their intensive structural use remains limited due, between also other factors, to several peculiar damage mechanisms able to quickly degrade the mechanical properties and requiring high maintenance costs due to service interruptions needed for carrying out periodical non-destructive testing inspections. One solution, more and more suggested and proposed in the literature, is then to apply a structural health monitoring approach. The present paper investigates such possibility focusing on the application of the “Design of Experiment” methodology to the performance of Lamb ultrasonic waves-based monitoring carried out using piezoelectric transducers bonded on the surface of aeronautical laminates. The choice of a Design Of Experiment approach is based on the well-known fact tha...