Impact damage detection in filament wound tubes using embedded optical fibre sensors

Filament wound tubes are currently being used extensively in service because of their superior specific properties and the relatively simple manufacturing technique involved in their production. However, filament wound tubes can suffer from low-velocity impact damage (similar to 10 m s(-1)) during service. Such damage can result in poor post-impact properties which in certain applications can reduce the burst strength below safe working levels. This paper discusses the use of embedded optical fibre sensors for impact damage detection in filament wound tubes. The primary aim was to detect threshold levels of impact damage which would render the tube unsafe to use. Two types of sensor were used, namely (i) a simple crack detection system where the fracture of the optical fibres was correlated to the level of impact damage and (ii) a novel intensity-based optical fibre sensor which was used to measure the stiffness change in the filament wound tube as a function of impact damage. The first sensor was designed to be used on-line, i.e., during service, whereas the second sensor was designed for off-line analysis to provide more detailed information about the extent of impact damage. This study has demonstrated that it is relatively straightforward to embed the optical fibres into the filament wound tube during its manufacture. The majority of the optical fibres survived the filament winding and subsequent processing operation. The feasibility of using the simple crack detection system was successfully demonstrated. A novel intensity based optical fibre sensor was used to measure the stiffness change in the composite as a function of impact damage.