Papers by Keyword: Piezoresistivity

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Authors: Wei Min Gan, Zhang Guo Li, Xin Huang
Abstract: Cement mortar shows piezoresistivity after being mixed with small amount of graphite, thus the resistivity of the material will changed with stress. In this study, specimens embedded double electrodes which made of cement based material with small amount of graphite (3 wt.% of cement) are used in the experiments of one-time loading and cyclic loading, and the relative resistivity are measured by a series connected AC circuit. The results show that the specimens’ piezoresistivity goes down while the stress increases, and different curves of piezoresistivity can be observed in experiments with different loading methods. The relative resistivities of the specimen show a similar change as strain.
Authors: Kraisit Loamrat, Manote Sappakittipakorn, Piti Sukontasukkul
Abstract: The aim of this research was to implement cement-based sensors in monitoring the change of strain in concrete structures in particular where a compression applies. The experiment was conducted in a laboratory by embedding a cement-based sensor in a 150x150x150 mm normal strength concrete cube. When the sensor-installed concrete cube was loaded, the relation between the fractional change in resistivity (FCR) and strain of the sensors was evaluated. In this study, all cement-based sensors were made of cement paste containing carbon fiber at 2% by volume fraction. They were then varied with the addition of graphite powder at 4% and silica fume at 15% by weight of cement. Thus, there were total four mix proportions. From the experimental results, all sensors provided a good corelation between the FCR and compressive strain. Among them, the carbon fiber plus graphite powder (no silica fume) cement-based sensor yielded the most excellent piezoresistive response.
Authors: Giancarlo Canavese, Mariangela Lombardi, Stefano Stassi, Candido F. Pirri
Abstract: This work presents a comprehensive investigation of the piezoresistive response of a metal-polymer composite for robotic tactile sensor application. Composite samples, based on nickel nanostructured conductive filler in a polydimetihylsiloxane (PDMS) insulating elastomeric matrix, were prepared changing several process parameters like thickness, composition of the polymer and nickel filler content. A variation of electric resistance up to nine orders of magnitude under applied uniaxial load was measured in the fabricated samples. Cost efficient materials, simplicity of the process, large sensibility, and harsh environment compatibility make this quantum tunnelling composite adapted to be integrated as sensing coating in space robotic applications.
Authors: Yoshinobu Shimamura, Kyohei Kageyama, Keiichiro Tohgo, Tomoyuki Fujii
Abstract: Carbon nanofiber (CNF) has good electrical conductivity. Addition of a few percentages of carbon nanofiber to polymer yields electrical conductivity but hardly affects the mechanical properties of polymer. This conductive polymer may be useful for sensing applications such as strain sensors and chem-resist sensors. Many researchers have reported on the electrical conductivity, but the electrical resistance change under strain of the carbon nanofiller composites is not fully investigated. In this study, the electrical resistance change under strain of CNF/flexible-epoxy composites was investigated experimentally. More than 100% of quasi-static strain can be measured by using CNF/flexible-epoxy composite with Young’s modulus of less than 1MPa. Cyclic and unloading behaviors were also measured and discussed. It was found that the cyclic behavior was strongly affected by viscoelasticity and damage.
Authors: Akira Todoroki, Roysuke Matsuzaki, Yusuke Samejima, Yoshiyasu Hirano
Abstract: Authors’ group has been done researches on the damage monitoring of the laminated Carbon Fiber Reinforced Plastic (CFRP) using the electrical resistance change method. The method adopts reinforcement carbon fibers as sensors, and it is called self-sensing method. Using thin CFRP laminates, delamination crack location and dimension are identified with the electrical resistance change method. However, the electrical resistance decreases when a delamination crack is made in a thick CFRP beam. The present paper experimentally investigates the effect of the dent for the measurements of electrical resistance change. Indentation tests are performed for the thick CFRP plates. The effect of the dent is calculated compared with the effect of piezoresistivity caused by the residual stress relief. As a result, the effect of the dent is larger than the effect of the residual stress relief for the thick CFRP. For the thick CFRP, dents cause the significant reduction of the electrical resistance in the thickness direction, and that causes electrical resistance decrease.
Authors: Ren Juan Sun, Shan Shan Wei, Zhi Qin Zhao, Da Wei Huang, Zhi Ge
Abstract: This paper studied the electrical resistivity and piezoresistivity of specimen of cement paste made with multiwall carbon nanotubes (MWNTs). The twelve sodium dodecyl benzene sulfonate (SDBS) was used as surfactant. Specimen had a MWNTs to SDBS ratio of 1/4 and contained 0.2% NWNTs by weight. Different dispersal durations, 15min, 30min, 45min, were adopted. The test results show that under the same period of curing, when the dispersal time of MWNTs was 45min, the electrical resistivity of the composite was the biggest and the curve was the varied;with the age growth, the electrical resistivity increased obviously;with the increase of moisture content, the resistivity decreased significantly.
Authors: Koichi Nakamura
Abstract: The piezoresistivity for force sensing in wurtzite-ZnO nanowires with [0001] orientation has been simulated on the basis of the first-principles calculations of model structures. According to the difference in wall structure, our devised nanowire models can be divided into three groups by their conductivities; no band-gap conducting models, direct band-gap semiconducting models, and indirect band-gap semiconducting models. The strain responses to carrier conductivity of n-or p-doped semiconducting wurtzite-ZnO[0001] nanowire models were calculated using band carrier densities and their corresponding effective masses derived from the one-dimensional band diagram by our original procedure for a small amount of carrier occupation. The conductivities of p-type direct band-gap models change drastically due to longitudinal uniaxial strain in the simulation: the longitudinal piezoresistance coefficient is 120 × 10–11 Pa–1 for p-type (ZnO)24 nanowire model with 1% compressive strain at room temperature.
Authors: Xiao Xiang Zhang, Long Ba
Abstract: The nanocomposites of carbon nanotube/polymer have been studied to explore their piezoresistance properties, which can be used as smart materials in the fields like biomedical engineering, robotic engineering, and advanced instrumentation. The differences in piezoresistance behavior of the previous studies were explained by the less uniformity of carbon nanotubes. To clarify the resistance versus deformation relations for carbon nanotube/silicone rubber composite materials, we have fabricated composite materials with various nanotube and carbon black contents. The measurements show that the resistance versus deformation sensitive range is depends on both the content of nanotube and carbon black, while the tiny variation of content of the carbon black affects largely the total piezoresistance sensitivity and repeatability. The experiment shows that adequate amount of carbon balck mixed with carbon nanotube can improve the piezoresistance repeatability. The deformation induced variation of the conducting percolation network shall be the dominating mechanism for the piezoresistance behavior of carbon nanotube/silicone rubber composites.
Authors: Shakoor Abdul, Zheng Gan Zhou
Abstract: Eddy current method can be used for non-destructive assessment of residual stress. In order to relate electrical conductivity change to the residual stresses in the welded joints, piezoresistivity of 5A06 has been investigated using samples heat treated at 2500C and 4000C. These samples represent weld zones with different thermal exposure. A directional eddy current probe with a Hall Effect sensor was used to evaluate stress coefficient of electrical conductivity due to applied uniaxial tensile load on the samples. The electromagnetic forward model was solved using FEM package and linear conductivity inversion was formulated to express probe output in terms of electrical conductivity. The piezoresistivity coefficients of samples, calculated from the derivative of stress-conductivity relation, were compared. The results indicate that coefficients vary inversely with annealing temperature.
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