Experimental three-point bending test of glass fibre aluminium honeycomb sandwich panel with acoustic emission damage assessment

Due to their complexity, detecting and analysing damage modes in composite honeycomb sandwich panels can be difficult. This article describes the way in which a three-point bending test (3PBT) was performed on a glass fibre aluminium honeycomb sandwich panel (HSP). Acoustic emission (AE) was used to identify damage signals, which were then analysed to determine the positions and characteristics of defects. To locate damage positions, Delta-T mapping was used. The test load was progressively applied in three phases, with the specimen being inspected visually during each phase. A scanning electron microscope (SEM) showed that the most significant damage was local crushing under the test load, which caused matrix cracking, fibre breakage and pull-out. Damage progression and the damage mode were detected using the cumulative energy and frequency spectra of the AE sources for each phase. Matrix cracking frequencies ranged from 30 kHz to 100 kHz, while fibre damage modes ranged from 157 kHz to 322 kHz. The findings highlighted the utility of Delta-T mapping in locating damage positions on sandwich structures under testing. The investigation also emphasised the value of studying frequency spectra and cumulative energy when analysing AE signals.