The propagation characteristics of stress wave have been investigated for polymethyl methacrylate (PMMA) and unidirectional carbon/epoxy composites. Using these characteristics, the effects of propagation medium on the waveform and source characterization of acoustic emission (AE) signal due to vertical force at the epicenter have been calculated numerically.
Attenuation and dispersion effects have distorted the AE waveform by increasing the rise time and changing the amplitude. Source characterization of the AE signal in highly dissipative and dispersive medium using Green's function calculated under elastic assumption has produced erroneous results for the rise time and waveform. The source function deconvoluted from the detected waveform on PMMA plate using an optical probe has agreed with the numerically predicted waveform.
AE signals generated by pencil lead breakage and steel ball drop have been measured by a piezoelectric transducer at the same position on A12024 plate. Peaks in the spectra of the signals have appeared at the respective corresponding frequencies. The result has suggested that the spectral content of the received signal is dominated by the natural frequency response of the specimen. The peaks in the spectra of PMMA plate have been shifted to lower frequencies as the temperature increases, showing the change of the vibration frequency of the plate.
