Characteristic Research Of Carbon Fiber Smart Layer And Its Field Monitoring

Recently, structural health monitoring(SHM) in civil engineering had received considerable attention with the development of super long-span structure and super high-rise building. In this dissertation, sensor characteristics of carbon fiber smart layer were researched theoretically and experimentally. A new visual method of monitoring civil engineering structures was put forward. A skin-like sensor was designed through covering the carbon fiber smart layer on the surface of the civil engineering structures. Taking advantage of its character of function and conductivity to transform its strain field or stress field into electrical field which was easy to examine. Finally, the visual field monitoring of civil engineering was realized through applying the Electrical Resistance Tomographic (ERT) technology. The innovations in this dissertation were as follows:1. A new strain sensor was put forward using a carbon fiber smart layer. The sensor characteristic and interface treating method of the resin based smart layer and the cement based smart layer were researched through large quantity experiments. A new monitoring method of civil engineering was established based sensor field.2. The carbon fiber smart layer theoretically modal of piezoresistive effect was established in the situation of complex stress. The piezoresistive matrix was reduced in the situation of plane stress. It supplied theoretically based for field monitoring. It made the function characteristic research of carbon fiber smart material broke through experiment to theory, through one dimension to two dimensions.3. The carbon fiber smart layer was covering on the surface of structure the first time. Based on the sensor function characteristic and conductivity of smart layer, the theory method of field strain monitoring for structure was established successfully using ERT technology.4. A set of ERT system of carbon fiber smart layer was developed the first time, and was verified by the experiments. The new diagnose method was realized, which included image and visual of SHM. The integration of smart system from model, experiment to theory was realized. The research works in this dissertation were as follows:1. Through uniaxial tension and cyclic loading experiment of carbon fiber mat, we researched the deformation-resistance character, obtaining the strain gauge factor and sensitive limit by the experiment results. Considering the environment influence to resistance of carbon fiber mat, temperature- resistance character had been tested. Through the microcosmic experiment, the sensing mechanism of carbon fiber mat had been analyzed preliminary.2. The carbon fiber smart layer theoretically modal of piezoresistive effect was established. The piezoresistive matrix was reduced in the situation of plane stress. It supplied theoretically based for field monitoring. Laying carbon fiber mat in the resin to generate the resin based smart layer, as a strain sensor. The static characteristics were measured. Laying carbon fiber mat in the cement to generate the cement based smart layer, and covering it on the surface of sample beam as a strain sensor. The three-point vending test was done, in order to check about the pressure sensitivity, linearity, gauge factor, repeatability and uniformity of the fractional change in electrical resistance with structural average strain. The sensor function characteristics were researched covering the cement based carbon fiber smart layer on the surface of structure beam which had a crack. At the same time, the gauge factor was been greatly improved through doping a small amount short carbon fiber into the basal body.3. The ERT forward problems were studied. Its field was mathematically described using the finite element method(FEM). An ERT FEM system of smart layer was developed. The system had lots of function, such as area dividing, setting resistivity distribution, the ERT forward problem solving. The accuracy of the system was verified by the analysis solution for several typical resistivity distribution, and it was satisfied.4. The modified Newton-Raphson(MNR) method for ERT imaging was thoroughly studied, and the improved regularization method was applied for conquering the ill-posed of the inverse problems undertaking. A set of ERT imaging system of smart layer was developed, which had good imaging function. The accuracy of the system was verified. 5. The virtual experiment of the circular flat-plate was done under different load and different work condition. The resistivity distribution image was conversion through substituting data to the ERT system. The virtual experiment of actual engineering structure was done. The resistivity distribution image was conversion. The basic principles experiments of ERT system were done by circular flat-plates under different loading, which were coated rein based carbon fiber smart layer. The research showed that it was possible to monitoring the structure health using the ERT technology. The theory analysis and the system of carbon fiber smart layer were accuracy and usable. Furthermore, it was feasibility to whole monitoring the structure health using the function character of smart layer and ERT technology.