Smart properties of carbon nanotube-epoxy composites

Abstract

Intelligent smart materials can not only monitor the damage and degradation of architectural structures in real time but also the health structure. In recent years, carbon nanotubes materials have emerged to possess both excellent mechanical and electrical properties. Moreover, when carbon nanotubes are added to epoxy resin, intelligent composite materials with significant sensitivity are created. In this study, the stress–strain curves and anelasticity of carbon nanotube/epoxy resin composites with different carbon nanotube concentrations is analyzed. Through changing the level of carbon nanotubes using the two-pole method, the percolation threshold of carbon nanotube/epoxy composites was determined. Thereafter, the effect of temperature on the composites’ conductive properties was investigated. Moreover, using the stepwise cyclic loading method, the piezoresistivity of the carbon nanotube/epoxy composites was investigated. The test results show that the elastic limit, the yield point, and the elastic modulus range of the carbon nanotube/epoxy composites is approximately 45 MPa, 50 MPa, and 1–2 GPa, respectively. The anelasticity of the carbon nanotube/epoxy composites increases with the gradual increase of the stress level. The percolation threshold interval of carbon nanotube/epoxy composites ranges from 0.5 to 1.0 wt%. The rate of change of resistance for the different concentrations on carbon nanotube/epoxy specimens corresponds to the temperature. Notably, the carbon nanotube/epoxy composites have better discrimination and pressure sensitivity for different grades of load. When the carbon nanotube content is 0.5 wt%, the sensitivity of the carbon nanotube/epoxy composites pressure-sensitive property is the largest, which is in agreement with the threshold curve. The results of this investigation have implications for the application of carbon nanotube/epoxy composites in structural health monitoring.