Acoustic emissions from some stressed polypropylene—glass fibre composites have been studied. Pattern recognition has enabled several classes of signal to be identified. These classes and the distribution of the signals in them varies from material to material. By the use of an averaging technique a characteristic acoustic emission signal can be obtained for a particular type of material. Event timing used in conjunction with the data obtained by the analysis of individual signals has led to some speculation on the fracture processes involved.
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