scholarly journals Numerical Investigation on Guided Waves Dispersion and Scattering Phenomena in Stiffened Panels

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 74
Author(s):  
Alessandro De Luca ◽  
Donato Perfetto ◽  
Giuseppe Lamanna ◽  
Antonio Aversano ◽  
Francesco Caputo
Keyword(s):  
Composite Structures ◽  
Guided Waves ◽  
Mode Conversion ◽  
Analytical Data ◽  
Experimental Tests ◽  
Detection Sensitivity ◽  
Research Activity ◽  
Fe Method ◽  
Stiffened Panels ◽  
Reflected Waves

The aim of this work is to propose a numerical methodology based on the finite element (FE) method to investigate the dispersive behavior of guided waves transmitted, converted, and reflected by reinforced aluminum and composite structures, highlighting their differences. The dispersion curves of such modes can help designers in improving the damage detection sensitivity of Lamb wave based structural health monitoring (SHM) systems. A preliminary phase has been carried out to assess the reliability of the modelling technique. The accuracy of the results has been demonstrated for aluminum and composite flat panels by comparing them against experimental tests and semi-analytical data, respectively. Since the good agreement, the FE method has been used to analyze the phenomena of dispersion, scattering, and mode conversion in aluminum and composite panels characterized by a structural discontinuity, as a stiffener. The research activity allowed emphasizing modes conversion at the stiffener, offering new observations with respect to state of the art. Converted modes propagate with a slightly slower speed than the incident ones. Reflected waves, instead, have been found to travel with the same velocity of the incident ones. Moreover, waves reflected in the composite stiffened plate appeared different from those that occurred in the aluminum one for the aspects herein discussed.

A Numerical Approach for the Investigation of Guided-Waves Propagation Mechanisms in Reinforced Polymers through a DoE Analysis

2019 ◽  
Vol 957 ◽  
pp. 329-339
Author(s):  
A. de Luca ◽  
Donato Perfetto ◽  
Francesco Caputo
Keyword(s):  
Material Properties ◽  
Composite Structures ◽  
Guided Waves ◽  
Lamb Waves ◽  
Numerical Models ◽  
Detection Sensitivity ◽  
Fe Model ◽  
Structural Health ◽  
Waves Propagation ◽  
Local Material Properties

Thanks to their high damage detection sensitivity and low requested power consumption, guided-waves (Lamb waves) have been increasingly used in the last years to monitor the structural integrity in primary and secondary composite structures. The monitoring of the structural health through the propagation of Lamb waves in composite structures is notoriously complex and, for this reason, the development of a prediction model can be a helpful tool for the improvement of Structural Health Monitoring (SHM) systems. Finite Element Method (FE) appears to be the best candidate for such type of simulation. However, since Lamb waves propagation depends strictly on the local material properties of the medium they propagate through, their numerical characterization is a thorny phase. Real composite components are usually affected by the presence of a large number of voids and defects, which cannot be reproduced in numerical models; this leads to a variability of the mechanical properties of materials, with particular reference to elastic moduli and density. These aspects get really ambitious the development of a well-established FE model. In this paper, a design of experiment (DOE) has been carried out to numerically investigate on the effects of the material properties variability on guided-waves time of flight.

scholarly journals Fiber Bridging Induced Toughening Effects on the Delamination Behavior of Composite Stiffened Panels under Bending Loading: A Numerical/Experimental Study

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2407 ◽  
Author(s):  
Angela Russo ◽  
Mauro Zarrelli ◽  
Andrea Sellitto ◽  
Aniello Riccio
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Composite Structures ◽  
Numerical Procedure ◽  
Research Activity ◽  
Stiffened Panels ◽  
Mode I Fracture Toughness ◽  
Fiber Bridging ◽  
Out Of Plane ◽  
Bending Loading

In this paper, a research activity, focused on the investigation of new reinforcements able to improve the toughness of composite materials systems, is introduced. The overall aim is to delay the delamination propagation and, consequently, to increase the carrying load capability of composite structures by exploiting the fiber bridging effects. Indeed, the influence of fiber bridging related Mode I fracture toughness (GIc) values on the onset and propagation of delaminations in stiffened composite panels, under three-point bending loading conditions, have been experimentally and numerically studied. The investigated stiffened panels have been manufactured by using epoxy resin/carbon fibers material systems, characterized by different GIc values, which can be associated with the material fiber bridging sensitivity. Experimental data, in terms of load and delaminated area as a function of the out-of-plane displacements, have been obtained for each tested sample. Non-Destructive Inspection (NDI) has been performed to identify the debonding extension and position. To completely understand the evolution of the delamination and its dependence on the material characteristics, experiments have been numerically simulated using a newly developed robust numerical procedure for the delamination growth simulation, able to take into account the influence of the fracture toughness changes, associated with the materials’ fiber bridging sensitivity. The combined use of numerical results and experimental data has allowed introducing interesting considerations of the capability of the fiber bridging to substantially slow down the evolution of the debonding between skin and reinforcements in composite stiffened panels.

Advanced debonding detection technique for aerospace composite structures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Assunta Sorrentino ◽  
Fulvio Romano ◽  
Angelo De Fenza
Keyword(s):  
High Frequency ◽  
Composite Structures ◽  
Guided Waves ◽  
Plastic Material ◽  
Impact Damage ◽  
Small Scale ◽  
Content Type ◽  
Stiffened Panels ◽  
Reinforced Plastic ◽  
Debonding Detection

Purpose The purpose of this paper is to introduce a methodology aimed to detect debonding induced by low impacts energies in typical aeronautical structures. The methodology is based on high frequency sensors/actuators system simulation and the application of elliptical triangulation (ET) and probability ellipse (PE) methods as damage detector. Numerical and experimental results on small-scale stiffened panels made of carbon fiber-reinforced plastic material are discussed. Design/methodology/approach The damage detection methodology is based on high frequency sensors/actuators piezoceramics system enabling the ET and the PE methods. The approach is based on ultrasonic guided waves propagation measurement and simulation within the structure and perturbations induced by debonding or impact damage that affect the signal characteristics. Findings The work is focused on debonding detection via test and simulations and calculation of damage indexes (DIs). The ET and PE methodologies have demonstrated the link between the DIs and debonding enabling the identification of position and growth of the damage. Originality/value The debonding between two structural elements caused in manufacturing or in-service is very difficult to detect, especially when the components are in low accessibility areas. This criticality, together with the uncertainty of long-term adhesive performance and the inability to continuously assess the debonding condition, induces the aircrafts’ manufacturers to pursuit ultraconservative design approach, with in turn an increment in final weight of these parts. The aim of this research’s activity is to demonstrate the effectiveness of the proposed methodology and the robustness of the structural health monitoring system to detect debonding in a typical aeronautical structural joint.

Numerical Modelling and Experimental Verification of Interdigital Transducers for Lamb Wave Generation

2015 ◽  
Vol 220-221 ◽  
pp. 843-848 ◽  
Author(s):  
Michał Mańka ◽  
Adam Martowicz ◽  
Mateusz Rosiek ◽  
Łukasz Ambroziński ◽  
Tadeusz Uhl
Keyword(s):  
Experimental Verification ◽  
Guided Waves ◽  
Experimental Tests ◽  
Screening Tests ◽  
Computationally Efficient ◽  
Research Activity ◽  
Custom Made ◽  
Efficient Code ◽  
Materials Used ◽  
Analytical Relations

Recently, intensive research activity in the application of guided waves (GWs) for structural health monitoring (SHM) has been observed. Interdigital Transducer (IDT) is one of the types of transducers used for generating GWs. The main advantages of such transducers include their ability in generating directional and mode-selective waves. The parameters of IDTs have to be adjusted for the excited wavelength. Some geometric parameters as well as the properties of materials used for manufacturing transducers may be defined using widely known analytical relationships [1]. However, in order to accurately determine the parameters of the IDT, numerous simulations and their experimental verification are required [2]. The paper presents a novel, time efficient approach to the virtual prototyping of complex shaped transducers. The proposed procedure consists of the following four steps: (1) designing a transducer based on analytical relations, (2) approximate numerical simulations of designed transducers with a custom-made, computationally efficient code for screening tests, (3) detailed numerical tests employing the multiphysics Finite Element Method (FEM) for the developed IDT design and (4) experimental tests.

Core-Skin Disbond Detection in a Composite Sandwich Panel Using Guided Ultrasonic Waves

2017 ◽  
Vol 1 (1) ◽  
Author(s):  
Christoph Schaal ◽  
Ajit Mal
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Laboratory Experiments ◽  
Guided Waves ◽  
Sandwich Panel ◽  
Mode Conversion ◽  
Guided Wave ◽  
Ultrasonic Waves ◽  
Propagation Path ◽  
Composite Sandwich

Advanced composite materials are being increasingly used in state-of-the-art aircraft and aerospace structures due to their many desirable properties. However, such composite materials are highly susceptible to developing internal damage. Thus, safe operation of such structures requires a comprehensive program of effective nondestructive inspection and maintenance of their critical load bearing components before the defects grow and become unstable, resulting in failure of the entire structure. Ultrasonic guided wave-based methods have the potential to significantly improve current inspection techniques for large plate-like structural components due to the waves' large propagation range and sensitivity to defects in their propagation path. The application of guided waves for nondestructive evaluation (NDE) of real structures, however, requires a thorough understanding of the characteristics of guided waves in composite structures in the presence and absence of any defects. In this paper, the interaction of guided waves with a core–skin disbond in a composite sandwich panel is studied using a semi-analytical method, numerical simulations, and laboratory experiments. It is shown that the disbond causes complex mode conversion at its leading and trailing edges. The theoretical findings are verified with laboratory experiments, and the applicability of the proposed pitch–catch setup for NDE of complex composite structures for damage detection is discussed.

scholarly journals Longitudinal Guided Wave Inspection of Small-Diameter Elbowed Steel Tubes with a Novel Squirrel-Cage Magnetostrictive Sensor

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Yao Liu ◽  
Xiucheng Liu ◽  
Chehua Yang ◽  
Wenxin Guo ◽  
Bin Wu ◽  
...  
Keyword(s):  
Finite Element ◽  
Guided Waves ◽  
Mode Conversion ◽  
Small Diameter ◽  
Longitudinal Mode ◽  
Guided Wave ◽  
Wall Defect ◽  
Squirrel Cage ◽  
Simulation Results ◽  
Magnetostrictive Sensor

In the study, ultrasonic longitudinal mode guided waves were employed to detect defects in elbowed tubes (without welds) with a diameter of 10 mm. Finite element simulation results highlighted that the emitted L(0,1) mode guided waves experienced strong reflection and mode conversion at the elbow region to generate F(1,1) mode, followed by slow and weak F(2,1) mode. The guided wave reflected from the elbow with a through-wall defect was manifested as two overlapped wave packets, which were good indicators of a defective elbow. To conduct L(0,1) mode guided waves inspection on the small-diameter elbowed tubes, a novel tailored squirrel-cage magnetostrictive sensor was employed in the experiment. The new sensor employed the configuration of segmental iron-cobalt strips and small-size permanent magnet arrays. The entire sensor is composed of two identical C-shaped sensor elements and can be recycled and installed conveniently. Experimental results obtained from healthy and defective tubes were consistent with the conclusions obtained from finite element simulations. An artificial through-wall defect at the elbow and a notch defect at the straight part of the tube could be simultaneously detected by L(0,1) mode guided waves through comparing experimental signals with simulation results.

scholarly journals Water Level Sensing in a Steel Vessel Using A0 and Quasi-Scholte Waves

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Peng Guo ◽  
Bo Deng ◽  
Xiang Lan ◽  
Kaili Zhang ◽  
Hongyuan Li ◽  
...  
Keyword(s):  
Water Level ◽  
Guided Waves ◽  
Mode Conversion ◽  
Experimental Studies ◽  
Low Frequency ◽  
Steel Vessel ◽  
Theoretical Predictions ◽  
Travelling Time ◽  
The Comparative Study ◽  
Group Velocities

This paper presents a water level sensing method using guided waves of A0 and quasi-Scholte modes. Theoretical, numerical, and experimental studies are performed to investigate the properties of both the A0 and quasi-Scholte modes. The comparative study of dispersion curves reveals that the plate with one side in water supports a quasi-Scholte mode besides Lamb modes. In addition, group velocities of A0 and quasi-Scholte modes are different. It is also found that the low-frequency A0 mode propagating in a free plate can convert to the quasi-Scholte mode when the plate has one side in water. Based on the velocity difference and mode conversion, a water level sensing method is developed. For the proof of concept, a laboratory experiment using a pitch-catch configuration with two piezoelectric transducers is designed for sensing water level in a steel vessel. The experimental results show that the travelling time between the two transducers linearly increases with the increase of water level and agree well with the theoretical predictions.

Application of the Beam-Forming Technique for Damage Detection in Composite Plate

2012 ◽  
Author(s):  
Ernesto Monaco ◽  
Fabrizio Ricci ◽  
Leonardo Lecce ◽  
Natalino Daniele Boffa
Keyword(s):  
Guided Waves ◽  
Angular Position ◽  
Experimental Tests ◽  
Time Shift ◽  
Beam Forming ◽  
Explicit Finite Element ◽  
Cfrp Plate ◽  
Specific Direction ◽  
Sensors Array ◽  
Beamforming Technique

The utilization of guided waves generated and sensed by an array of phased sensors allows steering the wave-front in a specific direction (beamforming technique). In this work a linear array of sensors is used to generate an ultrasonic wavefront steered in a specific direction. Numerical simulations are carried out with the LS-DYNA, an explicit Finite Element (FE) code, on a CFRP plate. The damage to be identified is a delamination produced by an impact (BVID). The array of sensors consists of a number of disk-shaped piezo patches. From the echo reflected and returning back to the array, it’s possible to evaluate the time of flight of the signal (TOF) from which the distance of the damage from the sensors array can be determined, and the angular position of the crack by evaluating the time shift of the signal received by each sensor in the array. The experimental tests are carried out in a 0.5m × 0.5m ×2.2 mm CFRP plate with the same sensor array and delamination used in the simulation. A number of receivers located along the panel edges have been also used to detect the damage direction in pitch-catch mode.

Semi-analytical modelling of guided waves generation on composite structures using circular piezoceramics

2015 ◽  
Author(s):  
Pierre-Claude Ostiguy ◽  
Nicolas Quaegebeur ◽  
Maxime Bilodeau ◽  
Patrice Masson
Keyword(s):  
Composite Structures ◽  
Guided Waves ◽  
Analytical Modelling

scholarly journals Numerical Simulation on Micro-damage Detection In CFRP Composites Based on Nonlinear Ultrasonic Guided Waves

2021 ◽  
Keyword(s):  
Damage Detection ◽  
Composite Structures ◽  
Guided Waves ◽  
Second Harmonic ◽  
Wave Mode ◽  
Guided Wave ◽  
Reinforced Plastics ◽  
Matrix Cracks ◽  
Nonlinear Ultrasonic ◽  
Contact Acoustic Nonlinearity

Abstract. Micro-damages such as pores, closed delamination/debonding and fiber/matrix cracks in carbon fiber reinforced plastics (CFRP) are vital factors towards the performance of composite structures, which could collapse if defects are not detected in advance. Nonlinear ultrasonic technologies, especially ones involving guided waves, have drawn increasing attention for their better sensitivity to early damages than linear acoustic ones. The combination of nonlinear acoustics and guided waves technique can promisingly provide considerable accuracy and efficiency for damage assessment and materials characterization. Herein, numerical simulations in terms of finite element method are conducted to investigate the feasibility of micro-damage detection in multi-layered CFRP plates using the second harmonic generation (SHG) of asymmetric Lamb guided wave mode. Contact acoustic nonlinearity (CAN) is introduced into the constitutive model of micro-damages in composites, which leads to the distinct SHG compared with material nonlinearity. The results suggest that the generated second order harmonics due to CAN could be received and adopted for early damage evaluation without matching the phase of the primary waves.

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