Acoustic emission (AE) testing is a sensitive technique capable of detecting many types of defect with a sparse sensor array making it an attractive structural health monitoring technology. The widespread application of the technology is limited by a lack of predictive modelling and in part, the lack of quantitative source characteristics. The vast majority of current laboratory AE testing is conducted on small coupons which cannot be used to generate quantitative source characteristics since reflected wave energy from the specimen edges influences the received waveforms. An alternative approach is to test on large specimens where the modal properties of propagating waves can be examined with no influence from reflected wave energy. However, the design and testing of large specimens is not trivial. The work in this paper discusses the design of large fibre reinforced composite (FRC) specimens which are suitable for making quantitative source measurements. The design considerations include the minimum plate dimensions and placement of sensors. A novel technique, referred to as the location-time plot technique, is described which links propagation characteristics, specimen dimensions and sensor locations to map the dispersion of elastic waves in plates. The technique is demonstrated in the design of a simple AE experiment on a highly anisotropic plate. The technique is then used in the design of a practical AE testing arrangement for monitoring delamination from artificial defects in a large FRC plate. Experimental waveforms, recorded using this AE testing arrangement, are presented and are shown to be in agreement with the location-time plot technique.

Date Published: 26 March 2009
PDF: 10 pages
Proc. SPIE 7294, Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2009, 729405 (26 March 2009); doi: 10.1117/12.815318

Published in SPIE Proceedings Vol. 7294:
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2009
H. Felix Wu; Aaron A. Diaz; Peter J. Shull; Dietmar W. Vogel, Editor(s)