A New Concept for Structural Health Monitoring Applied to Composite Materials. Part II: Experimental Validation

摘要

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 present a great sensitivity to detect damages inducing local variations of electric characteristics such as burning and liquid ingress. However, the sensitivity towards mechanical damages such as delaminations is clearly smaller, contrary to acousto-ultrasonic methods. The theory on which the electromagnetic technique lies are presented in a companion paper. Based on the complementarity of the two techniques, electromagnetic and acousto-ultrasonic, a new concept is proposed, combining them in an unique Structural Heath 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.