This paper demonstrates an approach for rapid non-contact air-coupled ultrasonic inspection of composite ailerons with complex cross-sectional profile including thickness changes, curvature and the presence of a number of stiffeners. Low-frequency plate guided ultrasonic modes are used in B-scan mode for the measurements in pitch-catch mode. Appropriate probe holder angles suitable for generating and receiving lower order guided wave modes are discussed. Different embodiments of the pitch-catch tandem positions along and across stiffener and curved regions of the test sample enable a rapid test campaign capturing the feature-rich sample profile. Techniques to distinguish special features in the stiffener are presented. © 2016 AIP Publishing LLC.

Prabhu Rajagopal

Department of Mechanical Engineering

Krishnan Balasubramaniam

Rabi Sankar Panda

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

Rapid non-contact inspection of composite ailerons using air-coupled ultrasound

AIP Conference Proceedings

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

In the present work, the interaction of the fundamental anti-symmetric guided Lamb mode (Ao) with a structural discontinuity in a composite structure was studied through Finite Element numerical simulations and experiments. The structural component selected for this study was a T-joint section made from glass/epoxy material. This co-cured composite structure is made-up of an upper shell (skin) and a spar as the sub-components. It was observed that when Ao mode interacts with the junction (structural discontinuity) of these sub-components, a mode-converted So mode is generated. Experiments were conducted using air-coupled ultrasound to validate the numerical simulations. The back-propagating "Turning modes", which propagate from the thin region to the spar web and vice versa, were also numerically simulated and experimentally verified. © 2010 Elsevier B.V. All rights reserved.

Ultrasonics

Interaction of Lamb mode (Ao) with structural discontinuity and generation of "turning modes" in a T-joint

The quantitative assessment of both, the length and width, of a delamination in quasi-isotropic composite laminates, using experimentally generated B- and D-scan imaging techniques employing ultrasonic Lamb waves was presented. Distinct zones were identified in B- and D-scans and the sizes of zones were expressed in terms of the width and length of delamination, the probe separation distance, and the probe diameter. B-scans generated through numerical simulations gave an insight and significance of each zone. B- and D-scans were used to estimate the width and length of delaminations, respectively. The estimated width and length of delaminations were found to be in concurrence with the actual values. © 2011 Elsevier Ltd.

Journal	Data powered by TypesetAIP Conference Proceedings
Publisher	Data powered by TypesetAmerican Institute of Physics Inc.
ISSN	0094243X
Open Access	No