This work investigated feasibility of Lamb wave based SHM technique for in-situ monitoring of hidden (inaccessible) web region, for delamination type of defect, in a typical stiffened composite (I-joint) section of an aircraft structure. Finite element model was proposed to understand and compare the wave propagation of fundamental symmetric Lamb mode (S0) through a healthy and center delaminated web of the I-joint. In simulations, S0 mode was excited at the center of web, which then, travels along the web and propagates into skin regions of the I-joint. Turning modes were also observed. From the S0 mode captured at two locations on the skin, one for the direct mode and another for the turning mode, it was seen that amplitude of the captured mode can used as a feature for delamination detection. Experiments were carried out on the I-joint with bonded piezoelectric wafer active sensor patch on the web and skin regions. In order to reduce the weight of the SHM instrumentation, an attempt was made to develop a low footprint, portable instrumentation for actuation, and reception of Lamb waves and wireless live transmission of the ultrasonic data. Experimental measurements showed a similar trend of significant decrease in the amplitude of S0 modes when propagating through the web delamination when compared to simulation. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Krishnan Balasubramaniam

Department of Mechanical Engineering

Aircraft manufacture

Airframes

Structural health monitoring

Surface waves

Ultrasonic waves

Ultrasonics

Wave propagation

AIRCRAFT STRUCTURE

COMPLEX COMPOSITE STRUCTURES

DELAMINATION DETECTIONS

I-JOINT

PIEZOELECTRIC WAFER ACTIVE SENSORS

PORTABLE INSTRUMENTATION

PWAS

STIFFENED COMPOSITE

Delamination

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Structural Control and Health Monitoring

This article reports on the characterization of delamination damages in composite laminates using wave visualization method. A combination of plate-guided ultrasound and air-coupled ultrasonics is used to locate and visualize delaminations. The study focuses on the physics of Lamb wave propagation and interaction with delaminations at various through-thickness locations and positions. Three-dimensional finite element simulations are used to study, in detail, the changes in wave features such as mode velocity, wavelength and wave refraction in the delamination region. These wave features provide information on the location, position and orientation of the delamination. These studies are validated by experimental measurements. The influence of position of source and delamination on wave refraction in the delamination region is examined. This method also correlates the results obtained from experiments and finite element simulations to theoretical dispersion curves in order to distinctly determine the delamination location. © 2016, © The Author(s) 2016.

Fulltext

Structural Health Monitoring

Characterization of delamination-type damages in composite laminates using guided wave visualization and air-coupled ultrasound

Composite materials are today widely used in engineering applications because of superior strength-weight ratios offered by them as well as high structural performance and corrosion resistance. However defects such as fibre breakage, matrix cracking, de-bonding and delaminations in composites impact their structural integrity and reliability negatively and NDE techniques to rapidly identify such defects are valuable. Ultrasonic guided waves have over the years emerged as attractive tools for scanning of large structures and recently they have been considered for rapid inspection of plate and pipe installations. Air-coupled ultrasound for generation of Lamb waves is particularly attractive for composite applications in view of the non-contact inspection offered, as well as the possibilities for rapid mechanized scanning. In this paper we present damage identification and visualisation approaches for quasi-isotropic composite plate structures, based on air-coupled plate guided ultrasonic (Lamb) waves. In the implementation demonstrated, an 8-layered quasi-isotropic [0/+45/-45/90]s glass fibre reinforced plastics (GFRP) composite plate is interrogated using air-coupled pitch-catch guided ultrasound. Propagation of Lamb waves in the laminates and their interaction with delaminations of different sizes at various locations along the structure are studied using 3D finite element (FE) analysis. The visualization approach is validated using experiments, leading to quantitative predictions of defect parameters such as sizing, location and depth. The approach is also extended for the inspection of complex composite structural features such as I- and T-sections. © 2015 AIP Publishing LLC.

AIP Conference Proceedings

An approach for defect visualization and identification in composite plate structures using air-coupled guided ultrasound

Propagation of the anti-symmetric fundamental Lamb mode (A0) in a composite laminate containing a semi-infinite delamination was studied through numerical simulations and experimental studies. Here, the wave was generated on a sub-laminate above the delaminated region, and the reflection and transmission of the Lamb modes at the edge of the discontinuity were quantitatively studied. The wave group (named as 'turning mode'), which was made to propagate from one side of the delamination to the other side (through delaminations) was captured and its transmission factor was estimated. Reflection and transmission factors of wave groups were estimated for three different laminates - quasi-isotropic, unidirectional and cross-ply, containing delamination at various interfaces across thickness. Propagation of 'turning modes' were also captured experimentally, employing air-coupled transducers, in quasiisotropic laminates containing delaminations at different interfaces. Attenuation compensation was incorporated in the experimental signals to improve the comparison of transmission and reflection factors between numerical simulations and experiments. © 2011 Elsevier Ltd.

Composite Structures

Numerical and experimental studies on propagation of A0 mode in a composite plate containing semi-infinite delamination: Observation of turning modes

A new compact sensor configuration comprising a single transmitter and multi-receivers (STMR) is presented for the in situ structural health monitoring (SHM) of large plate-like isotropic structures. The STMR exploits the long-range propagation characteristics of ultrasonic guided Lamb waves and a phase reconstruction algorithm to provide defect detection and location capability under non-dispersive as well as dispersive regimes of guided waves. Simulations are performed on defect-free and defective finite plates of aluminum to demonstrate the various features of the STMR system. Experiments were carried out on 1mm thick aluminum plates initially using a pair of individual sensors and subsequently using a prototype STMR array. The simulated results of the STMR performance were validated well through these experiments. Features of the STMR system such as its small footprint, the relatively simple data acquisition and processing discussed here have applications in the SHM of plate-like structures, and particularly of aerospace structures. © 2006 IOP Publishing Ltd.

Smart Materials and Structures

A single transmitter multi-receiver (STMR) PZT array for guided ultrasonic wave based structural health monitoring of large isotropic plate structures

Journal of Circuits, Systems and Computers

EVALUATION OF THE ULTRASONIC PREAMPLIFIER NOISE VOLTAGE DENSITY

Applied Composite Materials

Enhanced Composites Integrity Through Structural Health Monitoring

International Journal on Smart Sensing and Intelligent Systems

LAMB WAVE BASED MONITORING OF PLATE-STIFFENER DEBODING USING A CIRCULAR ARRAY OF PIEZOELECTRIC SENSORS

Lamb-wave-based structural health monitoring technique for inaccessible regions in complex composite structures

Journal	Data powered by TypesetStructural Control and Health Monitoring
Publisher	Data powered by TypesetJohn Wiley and Sons Ltd
ISSN	15452255
Open Access	No