Quantitative characterization of interface delamination in composite T-joint using couplant-free Lamb wave methods

Abstract

Need for quick NDE methods during field maintenance of aircraft has become a focus of attention due to increase in use of co-cured skin-stiffened composite structures. When Lamb wave propagates over skin-stiffened structures, the occurrence of multiple modes is unavoidable due to structural features such as stringers and stiffeners, which in turn makes the interpretation of received wave difficult and limits the defect-detection ability of Lamb waves. Using finite element simulations, propagation of incident S 0 Lamb mode in a typical composite T-joint with delamination between the flange and skin (interface) is investigated. Arrival time delays of the out-of-plane mode-converted wave packets are found to be a promising indicator for quantitative detection and sizing of the delamination. A novel experimental technique by combining a liquid couplant-free transduction scheme using dry-coupled roller transducer (contact probe) for generating S 0 mode with an air-coupled transducer (non-contact probe) as a receiver is proposed. This transduction scheme helps in selectively separating mode-converted wave packets. This investigation also establishes quantitative B-scan imaging method for characterization of delamination in the T-joint. Experimental result shows a good agreement with finite element predictions. Proposed method being single sided and couplant free has a potential to be utilized for field applications.

A study on the use of fundamental antisymmetric-like guided wave for health monitoring of elastic–viscoelastic bilayer structures

“…The conventional methods pose drawbacks like point-by-point inspection and time-consuming to inspect larger areas. 2,12 Ultrasonic guided wave techniques have been widely used in recent years due to their reliable, rapid and wide range detection advantages. 2,13,14 Guided wave inspection of bonded elastic-viscoelastic multilayered structures, frequency and mode selection are well described elsewhere.…”

“…The conventional methods pose drawbacks like point-by-point inspection and time-consuming to inspect larger areas. 2,12…”

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

“…Over the last decade, studies on the interaction of Lamb waves with delamination-type defects have been reported by many researchers in composite laminates. 5–9…”

“…Over the last decade, studies on the interaction of Lamb waves with delamination-type defects have been reported by many researchers in composite laminates. [5][6][7][8][9] Of the various transduction methods available, aircoupled ultrasonic testing (AUT) technique is emerging as a promising method for non-contact inspection of composites. 7,[10][11][12] The advantages of AUT include rapid automated scanning, excitation of a pure Lamb wave mode 11,13 and inspection of irregular and inaccessible regions.…”