A health monitoring system is presented composed of integrated
disc-shaped, 100 µm thick and 5 mm diameter piezoelectric transducers
(PZTs) working sequentially as Lamb wave emitters and receivers.
The diagnostic is based on the analysis of Lamb wave signals recorded before
and after damage. In the composite, delaminations are discontinuities
producing mode conversion processes generating various outgoing modes. The
multiresolution processing allows the isolation of various propagation modes
and their extraction in order to measure, for various propagation paths, the
time delay between the arrivals of the main burst and of a specific outgoing
mode. This process permits, with good accuracy, the localization of damage and
the estimation of its extent. The robustness and portability of this technique
is demonstrated by the fact that, after validation in our laboratory, it was
successfully applied to data coming from an experiment conducted in another
laboratory using its own acousto-ultrasonic health monitoring hardware
system.
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.
In composite materials, delaminations are discontinuities producing mode conversion processes generating various outgoing modes. The Discrete Wavelet Transform allows isolating various propagation modes and extracting them in order to measure the time delay between the arrivals of the main burst and a specific out-going mode, for various propagation paths. This process permits, with a good accuracy, to localize a damage and to estimate its extension.An active health monitoring system composed of integrated disc-shaped, 100 tim-thick and 5 mm-dia PZT transducers working sequentially as actuators and receivers is presented. The diagnostic is based on multiresolution process by wavelet transform applied on recorded Lamb wave signals obtained before and after damage. The robustness and portability of this technique is demonstrated by the fact that, after validation in our laboratory it was successfully applied to data coming from an experiment conducted in an other Laboratory using its own Health Monitoring hardware system.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.