This paper describes the use of acoustic monitoring techniques to identify specific failure mechanisms in composite materials. Because of their inherent complexity, composites exhibit a number of fracture modes depending on loading conditions and the properties and volume ratios of the constituents. The technique of fracture signature analysis attempts to use the frequency content and nature of the signals as a means for identifying specific critical events in the fracture process. Some of the difficulties associated with this technique are described together with a description of the techniques applied and results obtained with boron/epoxy.
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