Papers by Author: Timothy P. Bradshaw

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.

Abstract: A novel fibre optic sensor system has been developed for detection of acoustic emission. The sensor design was based on a 2×2 fused tapered optical fibre coupler configuration. Given the intended use of this sensor for the detection of acoustic emission in smart materials and structures, its lightweight, compatibility with composite material and immunity from electromagnetic interference are great advantages. Apart from the performance specification and reliability, the overall cost of the sensor system is a major factor in their adoption by end-users. The manufacturing of this sensor is low-cost and the signal output from the sensor system developed can be directly fed to the commercial AE acquisition system. The demonstration of acoustic emission detection was conducted using fibre coupler-based AE sensors in different materials and structures. The AE sources are various and depend on the different applications. In the current paper, we report on the use of the fibre optic AE sensor system for concrete damage monitoring. An experiment on damage detection on a composite plate with this fibre optical AE sensor is also reported in the paper.