DELAMINATION SIZING IN FIBER-REINFORCED PLASTICS USING PULSE-ECHO AMPLITUDE

In general, a '6 dB drop' method can be applied to size a delamination in a fibre-reinforced plastic. However; the accuracy of this method d epends on the size and shape of the delamination relative to the ultra sound beam. In addition, for small defects it may be impossible To obt ain the required 6 dB signal reduction. An alternative method for sizi ng small defects is by measuring the amplitude of the signal reflected by rite defect itself: This paper describes the simple amplitude meth od for delamination sizing and compares it with experimental results o btained using known defect sizes. The near-field region of the transdu cer, which is most commonly used for in-service delamination sizing, i s considered in these experiments. A comparison is also made with the results presented by Wong et al ill a recent publication. Finally, mea surements are made on standard defects embedded in a carbon-fibre comp osite panel. Despite verifying the theoretical treatment experimentall y, the amplitude method is not recommended in this paper for delaminat ion sizing in fibre-reinforced plastics because of the large uncertain ty levels.