A guided wave baseline approach to estimate the size and depth of delamination type defects in structural health monitoring of composites

Samaitis, Vykintas; Kaunas University of Technology; Lithuania

Mazeika, L.; Kaunas University of Technology; Lithuania
Samaitis, V.; Kaunas University of Technology; Lithuania

ID: ECNDT-0067-2018
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Session: Guided Waves techniques 3
Room: G3
Date: 2018-06-15
Time: 10:00 - 10:20

Ultrasonic guided waves have been widely used for structural health monitoring of various ageing engineering components to maintain their safe, reliable and optimal performance. Guided waves are sensitive to the change in elastic modulus of material and possess minor amplitude damping, which enables large structures to be inspected using only a few transducers and to detect both surface and internal defects. Recent developments related to the guided wave structural health monitoring aim to detect the structural changes only, which are later validated using conventional NDT methods. However, to avoid the false alarms, it’s important to estimate when the severity of damage becomes critical and the additional NDT methods must be applied. To achieve such goal, further information about the parameters of the damage is mandatory. Hence, the aim of this work was to develop an ultrasonic SHM technique which would enable the additional features of delamination type defects, such as size and depth to be extracted.
In this work the baseline ultrasonic method based on the interferential analysis of A0 mode reflecting within the delaminated area has been proposed. It was shown that proposed baseline method together with the frequency sweep excitation within the bandwidth of transducer enables the size and the depth of single delamination type defect to be determined. The performance of the proposed technique was proved with 2D/3D numerical simulations and experiments on the samples with artificial defects. Additionally, the feasibility of the proposed technique was tested on the models containing multiple parallel delaminations, which are common result of the impact damage. It was demonstrated that variations of excitation frequency and the developed baseline method with some limitations enables to extract additional features of the defects.