Initial Studies for AE Characterisation of Damage in Composite Materials

Abstract

Some initial studies for an AE characterisation of damage in composites are presented in this paper. A PAC AE PCI-2 based system and four PAC WD AE broadband sensors are used. Pencil lead breaks (PLB) were used to introduce a source of elastic waves. An initial validation of the system based on PLB on an aluminium plate showed that there was a large difference in sensitivity of the four nominally identical sensors. It is shown that the AE parameters are so strongly related to the sensitivity of the sensors that they tend to describe the AE system more than the actual sources. To characterise damage in composite materials alternative AE parameters are required that are not dependent on the sensitivity of the sensors. In the paper, it is shown that the frequency spectra of the sources have relatively little variability with respect to the sensor. A frequency-based approach that examines the spectrum of each source is proposed in the paper. The procedure is demonstrated using PLBs on a CFRP plate and it is demonstrated that the approach can indicate the position of the source in relation to orientation of the fibres and the plate edge.