Damage in carbon fibre composites: the discrimination of acoustic emission signals using frequency

This work considers the use of frequency content as a discriminating factor for acoustic emission (AE) signals from damage mechanisms in carbon fibre composite materials. Using a broadband conical transducer as an artificial source, investigations were made into the effects of source frequency (relaxation time), specimen geometry and sensor response on the frequency content of the recorded signals. It was shown that source frequency had an effect on the frequency content of the recorded signals, however, the specimen geometry and sensor response were shown to have a more significant effect. Additionally, AE signals were recorded from real damage mechanisms in tensile and beam buckling coupon specimens. The peak frequency content was used to examine signals resulting from the different damage modes identified. It was shown that some level of discrimination could be achieved and observations were in general agreement with previous research studies. However it was shown that great care is required when using peak frequency content as a discriminating factor because geometry and sensor response can have a distorting effect on the results.