Acoustic emission wave propagation in a viscoelastic plate

In loaded materials the strain-energy release due to microstructural changes results in stress-wave propagation. Acoustic emission deals with the recognition of such waves over the material surfaces and for this reason the application of acoustic emission techniques to the monitoring of the mechanical integrity of materials and structures is appropriate. Nevertheless, the use of such techniques in the case of polymer-based composite materials needs a clearer understanding of the relationships between the recorded signal, the damage process and the structure geometry. In this work a model is proposed of the propagation in a viscoelastic plate of waves due to a damage event. The microfailure event has been represented as a point source and ray theory has been applied to develop the physical model of wave propagation. The spectral analysis technique has been applied to the solution of the wave equations. Model calculations in the frequency domain have been compared with experimental spectra resulting from fiber breakage in different fiber/matrix systems from single-fiber fragmentation tests.