Load and deformation monitoring of composite pressure vessels by means of optical fibre sensors

This paper discusses the possibility of continuously monitoring the mechani cal behaviour of composite structures by means of optical fibre sensors. Op tical fibres have some inherent advantages which make them ideally suited f or this purpose. Optical fibres with intracore Bragg grating were chosen as an alternative to the classical strain gauges. The basic principles and pr operties of this sensor type are briefly discussed in the paper. Filament-w ound pressure vessels have been chosen as a representative composite struct ure and were equipped with surface-mounted as well as embedded optical fibr es. A test set-up has been developed to demonstrate the practical feasibili ty of performing remote condition monitoring. By means of selected loading cases, it is shown that the Bragg sensors are indeed very well-suited to mo nitor continuously load and deformation histories. The shift in Bragg wavel ength and the according strain show a nearly perfectly linear relationship with the pressure applied to the vessel. The Bragg sensors are also well-su ited for dynamic strain. monitoring. With additional research effort, and p rovided that adequate tools for the simulation of a degrading fibre-reinfor ced structure become available, permanent condition monitoring of critical structures can become realistic in the near future.