Feasibility of integrated optical fibre sensors for condition monitoring of composite structures. Part II: Combination of Bragg-sensors and acoustic emission detection

Abstract

This paper discusses the possibility of continuously monitoring the mechanical behaviour of composite structures by means of optical fibre sensors. In the first paper* some basic principles of optical fibre sensors in general and Bragg-sensors in particular have been briefly reported. Experimental results showed that optical fibre Bragg-sensors are much more reliable compared to traditionally used electrical-resistance strain gauges. In the introduction to this second paper, the discussion is extended to the broader context of condition monitoring. Filament wound pressure vessels have again been used as a representative composite structure. Instrumentation of the vessel consisted of an embedded Bragg-sensor, an acoustic emission detector and a pressure transducer. The results of a burst pressure experiment are discussed in this second paper. In this 'fully monitored' experiment, Bragg-sensors are used for strain monitoring and damage is monitored through acoustic emission detection. With additional research effort, and provided that adequate tools for the simulation of a degrading fibre-reinforced structure become available, permanent condition monitoring of critical structures can become realistic in the near future. The Bragg-sensor type can be considered a key instrument for monitoring applications of composite structures, provided that they become available at economically interesting prices.