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A novel non-linear elastic wave acoustic spectroscopy (NEWS) non-destructive inspection (NDI) method for aeronautic and spacecraft materials and components.

Robinson, D W*; Wright, J*; Gupta, S*; Mottram, T*; Armitage, P*; Gower, M R L; Lodeiro, M J; Gelat, P N; Schwarz, C* (2016) A novel non-linear elastic wave acoustic spectroscopy (NEWS) non-destructive inspection (NDI) method for aeronautic and spacecraft materials and components. CEAS Space J., 8 (1). pp. 35-45.

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Current non-destructive inspection (NDI) methods have limitations in their ability to identify certain flaws in complex materials and structures where a defect has not been fully formed, for example a kissing de-bond early-stage defect. Non-linear elastic wave acoustic spectroscopy (NEWS) methods have shown potential to detect early-stage flaws in metals and composites. The objectives of the ESA study reported here were to review the state of the art, then to design and build a breadboard demonstrator "NEWS Imaging" (NEWSI) non-linear acoustics instrument, and finally to demonstrate its capability using well-characterised reference defect artefacts (RDAs). A multi-mode NEWSI instrument was produced with the following modes of operation: (a) single and dual frequency, (b) pulse inversion, and (c) resonance drift modes. The first two are suitable for C-scan style imaging by contact testing or with the NACE (air-coupled detection) mode. A set of RDAs were sourced or manufactured, the most important of which was the development of successful kissing de-bonds; areas of significantly reduced bond strength, created in the bond-line between the composite laminates. All the RDAs were characterised by a wide range of complementary NDI methods, and the best results in terms of detection of all the known flaws was the scanning acoustic microscopy ultrasonic C-scan method. This technique detected all of the RDA defects except for kissing de-bonds. The NEWSI instrument was shown to be capable of detecting, with a certain degree of repeatability under controlled conditions, early-stage defects (kissing de-bonds) in composite materials. No other NDI method is known to detect these defect types. The results so far are encouraging and have potentially a lot of interest for ESA and the wider industry, if the unique capabilities of the NEWSI instrument demonstrated on the kissing de-bonds could be developed into a "routine practical test instrument". The target of the next stage of work is to bring the technology readiness level of the instrument up to pre-production levels of development.

Item Type: Article
Keywords: Non-destructive inspection, non-destructive testing, composite kissing de-bond defects, non-linear acoustic spectroscopy, space craft testing, early-stage defect detection
Subjects: Advanced Materials
Advanced Materials > Composites
Identification number/DOI: 10.1007/s12567-015-0104-2
Last Modified: 02 Feb 2018 13:13
URI: http://eprintspublications.npl.co.uk/id/eprint/7118

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