Health monitoring of composite structures by means of integrated piezoelectric sensors. Guy, P., Monnier, T., Goujon, L., & Jayet, Y. In Dai, Z. D., Qiu, J. H., & Liang, D., editors, SMART MATERIALS FOR ENGINEERING AND BIOMEDICAL APPLICATIONS, PROCEEDINGS, pages 163–170, Beijing, 2004. China Aviation Industry Press.
abstract   bibtex   
In previous papers we described a helpful health monitoring technique based on the use of guided waves generated by piezoelectric patches attached to the structure to be monitored. In this contribution, we will present some experimental results obtained on CFRP plates, submitted to low velocity impacts. A method allowing the detection of a damage in this laminated composite plane structure will be described. It consists in the definition of a number, called damage index (DI) that can be used to compare the health state of the structure at a given time with its reference state defined at the beginning of its lifetime. Two typical examples will be presented, to illustrate the advantages and the drawbacks of this method. Namely two experiments. involving antisymetric and symmetric guided modes respectively will be described., showing the different sensitivity of those modes to one kind of flaw. It is then possible to select one kind of wave to fit a given application. This method can apply to very complex structures with no need to identify each contribution observed in the waveforms. As far as a simple monitoring of eventual changes occurring in the structure under test is sufficient then the method is useful since it is very easy to implement for a very low cost. In the perspective of a quantitative health monitoring system design, the need of a full understanding of the propagation and interaction of guided waves with damages in a given structure will be discussed. So, in a second part of this work, the experimental results will be analyzed in relation with an analytical approach of the guided waves propagation in the laminated structure. Such an analytical study is limited to the case of damages of very simple shape. Nevertheless, it is a good qualitative tool allowing the prediction of the kind of guided wave to use in a given problem. For instance, it is possible to determine what guided mode will exhibit a maximum shear stress component at a chosen depth in the composite structure, thus increasing the sensitivity of the wave to a single delamination localized in that particular area. The case of realistic damages such as low speed impacts multiple delamination is examined through numerical calculations derived from a finite elements model. Preliminary results will be presented and discussed. In particular the mode conversions that can occur when the guided waves interact with multiple delaminations will be studied and interpreted. The actual requirements of the "ideal" health monitoring device will be defined and justified in accordance with the theoretical and numerical results.
@inproceedings{guy_health_2004,
	address = {Beijing},
	title = {Health monitoring of composite structures by means of integrated   piezoelectric sensors},
	isbn = {7-80183-378-3},
	abstract = {In previous papers we described a helpful health monitoring technique based on the use of guided waves generated by piezoelectric patches attached to the structure to be monitored.   In this contribution, we will present some experimental results obtained on CFRP plates, submitted to low velocity impacts. A method allowing the detection of a damage in this laminated composite plane structure will be described. It consists in the definition of a number, called damage index (DI) that can be used to compare the health state of the structure at a given time with its reference state defined at the beginning of its lifetime.   Two typical examples will be presented, to illustrate the advantages and the drawbacks of this method. Namely two experiments. involving antisymetric and symmetric guided modes respectively will be described., showing the different sensitivity of those modes to one kind of flaw. It is then possible to select one kind of wave to fit a given application. This method can apply to very complex structures with no need to identify each contribution observed in the waveforms.   As far as a simple monitoring of eventual changes occurring in the structure under test is sufficient then the method is useful since it is very easy to implement for a very low cost. In the perspective of a quantitative health monitoring system design, the need of a full understanding of the propagation and interaction of guided waves with damages in a given structure will be discussed.   So, in a second part of this work, the experimental results will be analyzed in relation with an analytical approach of the guided waves propagation in the laminated structure. Such an analytical study is limited to the case of damages of very simple shape. Nevertheless, it is a good qualitative tool allowing the prediction of the kind of guided wave to use in a given problem. For instance, it is possible to determine what guided mode will exhibit a maximum shear stress component at a chosen depth in the composite structure, thus increasing the sensitivity of the wave to a single delamination localized in that particular area.   The case of realistic damages such as low speed impacts multiple delamination is examined through numerical calculations derived from a finite elements model. Preliminary results will be presented and discussed. In particular the mode conversions that can occur when the guided waves interact with multiple delaminations will be studied and interpreted.   The actual requirements of the "ideal" health monitoring device will be defined and justified in accordance with the theoretical and numerical results.},
	language = {English},
	booktitle = {{SMART} {MATERIALS} {FOR} {ENGINEERING} {AND} {BIOMEDICAL} {APPLICATIONS}, {PROCEEDINGS}},
	publisher = {China Aviation Industry Press},
	author = {Guy, P. and Monnier, T. and Goujon, L. and Jayet, Y.},
	editor = {Dai, Z. D. and Qiu, J. H. and Liang, D.},
	year = {2004},
	keywords = {ageing monitoring, damage detection, guided   waves, multiple delamination, viscoelastic properties},
	pages = {163--170}
}
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