Acoustic Emission Analysis of Unidirectional Carbon Fiber Composite Plate

Acoustic emission (AE) is a typical technique for the study of various failure mechanisms of composite materials. However, such applications may be compromised due to the anisotropic nature of composite materials, where the acoustic signal velocity and attenuation depend on its traveling direction. This makes the correlation of the different failure modes to the recorded acoustic signals very difficult. In this paper, the influence of fiber orientation on AE signal was studied in unidirectional carbon fiber composite plate. Pencil lead breaks were used to introduce elastic waves. AE parameters such as counts, duration, energy, rise time and amplitude for aluminum and composite plate were analyzed in MS-Excel and results were compared to AE software. Good agreement was found between Excel and software on aluminum plate. Experiment on composite plate found that the most sensitive individual parameter to acoustic attenuation and fiber orientation (0°, 90°, 45°) is energy, and this sensitivity can be further improved if multiple parameters were combined together and evaluated as a whole. Acoustic velocities along various fiber directions were also theoretically studied and experimentally measured. Results showed that both velocity and AE parameters need to be used for signal analysis in AE inspection.