Acoustic emission in composite laminates

The response of a laminated plate to internal acoustic emission events is e xamined in detail. The plate consists of four layers of a unidirectional fi ber composite material arranged in a cross-ply configuration. The sources c onsidered include a vertical line couple, a horizontal line couple and a li ne double couple without moment. The latter is produced by the combination of two equal and opposite line couples and may be associated with a shear d islocation in the plane of the laminate. The particular response presented here is that of the normal upper surface displacement. Four different orien tations of the line sources relative to the core fiber direction are consid ered. The sources may be located at any depth within the plate and results are shown for three locations, namely, the upper interface, the midplane an d the lower interface. The receiver is positioned on the upper surface at a known distance from the line of action of the source. When this distance i s small relative to the depth of the plate, it is possible to associate som e of the peaks and troughs present in the response with the arrival of indi vidual rays. At larger distances, the disturbance arises from the propagati ng Rayleigh Lamb modes.