Strain sensing with CNT Nanocomposites: Static, cyclic and dynamic electromechanical material characterization

Carbon Nanotube (CNT) nanocomposites are one of the most important candidates to realize innovative strain sensors for Structural Health Monitoring (SHM) applications. In this work, the effect of static and dynamic strain on the electromechanical properties of carbon nanotubes (CNTs) nanocomposites, is investigated. In particular the nanocomposite is formed by multi-walled CNTs (MWNTs) embedded in a PolymethylMethacrylate (PMMA) matrix. The MWNTs randomly distributed within the PMMA matrix form conductive paths. These paths modify they morphology when the material is strained. Consequently the overall material conductivity changes. Continuous monitoring is possible by correlating these electrical changes to the deformation level of the material. Different specimens are made by varying the MWNTs content (3%, 5%, 7%, weight fractions) and are tested under varying static, cyclic and dynamic loading conditions. It is found that the Gauge Factor (GF) and nanocomposite sensitivity to strain, are directly related to the MWNTs content. Nanocomposites with higher MWNTs percentages (7%) show the best behaviour with a smaller dispersion of the experimental data. This data reproducibility is comparable to that of conventional strain gauges. The proposed functional material has the beauty of being ultralight and flexible. Moreover this material design has the potential of being scalable in size allowing continuous monitoring of larger structural areas than commercial sensors. The results shown in this paper highlight that this nanocomposite is a great candidate for the realization of advanced sensing devices.