A Hybrid Electromagnetic Acousto-Ultrasonic Method for SHM of Carbon/Epoxy Structures

Abstract

A model of electromagnetic behavior of composite materials like carbon/epoxy or glass/epoxy structures has been developed. Based on this model, an electromagnetic method allowing 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 wave crossing through the material has been also developed. A local measurement of magnetic and electric field allows to detect the presence and the extent of a damage if it induces a local variation of electric conductivity and/or electric polarization. This method presents a great sensitivity to detect damages inducing local variations of electric characteristics such as burning and liquid ingress. However, the sensitivity to mechanical damages such as delaminations is clearly lower, contrary to acousto-ultrasonic methods. Based on the complementarity of these two techniques, a new concept is proposed, combining them in an unique Structural Health Monitoring System (SHMS). The new SHMS which consists of a network of electromagnetic and ceramic piezo-electric sensors, is presented. The main results performed with this dual method applied to a carbon/epoxy structure including various defects (impact delaminations and local burning) are presented and discussed. Various images obtained by data reduction are presented.