Electromagnetic health monitoring system for composite materials

Office National d'Etudes et de Recherches Aerospatiales (ONERA), Structures and Damage Mechanics Department, 29 avenue de la Division Leclerc, B.P.72, F-92322 Chatillon cedex France

Abstract

A model of electromagnetic behavior o f composite materials such as carbon epoxy or glass epoxy structures has been developed. Based on this model, an electromagnetic method to evaluate the electric conductivity and the electric polarization of this type of material, by measurement of magnetic and electric components of an incident electromagnetic field crossing through the material, has been also developed. A Health Monitoring System (HMS) derived from this technique is presented, which allows to detect and characterize a wide variety of defects inside composite structures. The HMS is constituted of emitting and receiving networks sensitive to magnetic or electric fields, integrated into the composite structure. This system delivers electric images in which the damages can be detected and localized. Various electric images obtained by each type of measurement (magnetic and electric) and related to structures including various damages such as impact delamination, fiber breaking, local burning and liquid ingress, are presented and compared to images resulting from classical ultrasonic NDE. The complementary of the present technique with acousto-ultrasonic technique based on Lamb waves propagation, and the interest of combining them in a unique integrated system is evoked.