Title
Non-destructive inspection of carbon fibre-reinforced plastics using eddy current methods
Author
de Goeje, M.P.
Wapenaar, K.E.D.
Kunststoffen Rubber Instituut TNO
Publication year
1992
Abstract
The possibilities and limitations of eddy current methods for the inspection of carbon fibre-reinforced plastics have been investigated. The electrical properties of these composites lead to modifications of current methods applied to metals; in particular the required frequencies are much higher, 1-30 MHz for weave and 10-500 MHz for unidirectional reinforcements. A proper design of the probes is essential. Single turn coils are adequate, and it is shown how a higher sensitivity and suppression of the lift-off effect can be obtained. Fibre orientations can be detected conveniently with dedicated probes using a polar scan technique. The eddy currents are insensitive to delaminations. Only for unidirectional reinforcements and extensive delamination, over 20%, is the effect large enough to show up in C-scan images. In contrast, fibre fracture is readily detected for unidirectional and weave reinforcements, with a lower limit of about 8% fracture. As a result, eddy current methods are useful to establish the type of defect when a composite is damaged. This is confirmed by comparing eddy current and ultrasonic measurements on composites with impact damage.
Subject
Composite materials
Eddy current
Non-destructive testing
Ultrasonic inspection
Conductivity
Carbon fibre
Impact damage
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TNO identifier
536870
Publisher
Butterworth-Heinemann
Source
Composites, 23 (3), 147-158
Document type
article