Effects of Honeycomb Core on Acoustic Emission Wave Propagation in Glass Fibre Composite Plates

摘要

The objective of this article is to study in detail the acoustic emission wave propagation in a complex sandwich structure panel by utilising artificial Hsu-Nielsen acoustic emission sources. The sandwich panel consists of aluminium honeycomb core placed between two unidirectional glass fibre laminated plates. In order to study the effects of a bonded honeycomb core, artificial acoustic emission sources were generated on the top of a glass fibre laminated plate alone, at different angles relative to the fibre direction then repeated on the sandwich panel to find the change in (i) attenuations, (ii) wave velocities and (iii) frequencies of propagating acoustic emission waves. The attenuation of the waves increases after bonding the honeycomb in some directions. As an example, in direction 30°, the attenuation coefficient increases significantly from 5.252 dB./m to 10,27 dB/m whereas in 15° the change is small from 5.256 dB/m to 5.994 dB/m. On the other hand, the average velocity of acoustic emission in the plate has increased from 3527.02 m/s to 3836.85 m/s after bonding the honeycomb. However, in some other directions such as 0° direction, the average velocity has significantly reduced from 4028.41 m/s in the fibre glass laminated plate to 3637.36 m/s. Finally, wavelet transformation has been carried out on the waves in all directions and it is found that the active frequencies in the glass fibre laminated plate and the sandwich panel are in range from 30 kHz to 130 kHz. The results show that the presence of a bonder honeycomb core contributes significantly in changing to the acoustic emission propagation characteristics in the laminated glass fibre plates.