Acoustic Emission Detection of Incipient Failure of Fiberglass/Epoxy Laminates

Acoustic emission refers to the stress waves which are generated in materials during various dynamic processes. In some instances these emissions can provide an indication that damage is occurring in loaded structures. This paper presents the results obtained to date in a Boeing Vertol Company program to determine if acoustic emission methods can detect incipient failure of dynamically loaded fiberglass/epoxy laminates. The preliminary work reported herein indicates that the variation in acoustic emission count rate may correlate with incipient failure. There is evidence to show that the overall variation in count rate consists of a superposition of a number of individual variations of different frequency. At the present time a computer program is being prepared to perform Fourier analysis of the count rate variation. The objective is to determine if the count rate frequency spectrum correlates with incipient failure.