Determination of Damage Levels of Composite Plates after Low Velocity Impacts Using Acoustic Emission

Abstract

Eight composite plates 400x410x2.15mm were fabricated from carbon/epoxy in ((0,90)4)s lay-up. To ensure there was no damage in the plates prior to the impact investigations the plates were C-scanned. A drop test rig was used to apply a low velocity impact to the undamaged plates. A rebound mechanism was employed to prevent secondary impacts. AE sensors were selected for frequency and size due to the limited space on the test rig. Super glue was used both as a couplant and also to secure the sensors in position. During the impact wave streaming, time driven data and hit driven data were used to record the impact simultaneously. One test was conducted on each sample with two impacts completed at 5J, 6J, 8J and 10J (total of 8 samples). The impacts were designed to allow only slight visible impact damage to be formed. After completion of the impact investigation the plates were C-scanned to determine the area of debonded material. Analysis of the data showed the complete record of the impact event from the wave streaming, while the hit driven and time driven absolute energy data provided increasing correlations with the area of composite damaged.