Ultrasonic Inspection of Polymer Matrix Composites

Ultrasonic C-scan inspection techniques are widely used for the non-destructive evaluation of polymer matrix composites (PMCs). The techniques can be used to detect, measure and characterise a wide range of manufacturing and in-service defects in these materials. Although current use of this technique is primarily targeted at aerospace-type materials, a wider use is foreseen. NPL led a programme to identify and develop procedures suitable for standardisation.

A review was carried out to identify current industrial practices and requirements. The procedures were collected from the Industrial Advisory Group (IAG) associated with the project and other sources. The assessment covers procedures for the operation and calibration of C-scan equipment, and methods used for producing reference (calibration) panels incorporating typical defects. The IAG included both equipment suppliers and users.

The round robin (R-R) exercise was carried out with the IAG members scanning a trial reference panel using their existing procedures. The panel, a stepped carbon-fibre reinforced epoxy laminate containing defects of known size and location was produced at NPL. The aim of the R-R exercise was to identify the key parameters which influence inspection quality and to establish the degree of control required to obtain suitable repeatability and accuracy. In the final stage of the programme, panels were scanned by the IAG members using procedures formulated within the programme.

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