The health monitoring of composite materials: new approaches

The classical NDE techniques of periodical maintenance are just now evolving towards the continuous health monitoring of materials and structures. The on line monitoring systems have to present a small size without damage initiation risk, good sensitivity and robustness. Taking account of the relation of this approach with the more general notion of smart materials, it seems useful to extend this passive concept to a more active one specially in the case of composite materials. Effectively, if sensors are embedded in a composite structure before curing in order to monitor and optimise the processing parameters, they are able, remaining in the structure, to assume the health monitoring in the second stage of the life. Moreover, in slightly damaged systems, it becomes reasonable to use the collected results for an on line ten tative prediction of the residual life. Finally in the last stage of the life, when the material is deeply damaged, it is sometimes possible to slow down, and very rarely, to heal the damage