Smart Properties Research Of Carbon Fiber Reinforced Resin Composite

Carbon fibers possess a series of excellent characteristics of low density, high strength/weight ratio, enduring high temperature, electric conductivity, thermal conductivity and eroding resistance. Carbon fiber reinforced resin composite has become the research and application keystones of high and new techniques in China. Recently, the smart properties of carbon fiber reinforced composite were studied in China and the other countries. The smart material was used to manufacture the sensors than could sense the environmental changes. But the reported research on the smart properties of carbon fiber reinforced resin composite is very little. It is very necessary to perform a deep research on the smart properties of carbon fiber reinforced resin composite.The resin composites filled with short cut carbon felt and single direction continual carbon fibers are the research objects in this paper. The electric conductivity of carbon fiber reinforced resin composite was studied by a large number of tests when the outside conditions change in this paper. These outside conditions include environmental temperature, voltage, tensile stress, and bending load. By analysing the testing results, the relationships were gained between electric voltage and current, temperature and electric resistance, tensile stress and electric resistance, bending reformation and electric resistance. The smart properties of carbon fiber reinforced composite were proved, which meant that the changing of outside temperature, tensile stress and bending deformation could cause the electric resistance changing.For the resin composites filled with short cut carbon felt and single direction continual carbon fiber, the mathematics models were determined which expressed the direct ratio relationship between the single tensile stress and transverse, longitudinal volume resistivities by analysing the tensile-resistance measuring results. The one by one relationship between tensile stress and volume resistivity was proved, which indicate the resincomposites filled with short cut carbon felt can be used to manufacture the sensors. But the electric resistivity changed little when the tensile stress changed for the resin composites filled with single direction continual carbon fibers.The bending tests for the resin composites filled with short cut carbon felt Shown that the bending load had a little effect on the longitudinal resistivity and the transverse resistivity had a direct ratio relationship with the bending reformation of the sample.A series of tests about temperature-resistance sensitivity characters proved that the carbon fiber reinforced resin composites shown the PTC or NTC effects. The inner effect factors of the temperature-resistance sensitivity of the carbon fiber reinforced resin composites were analysed and discussed.For the resin composites filled with short cut carbon felt and single direction continual carbon fibers, electric current versus resistance testing proved that the electric conductivities of these kinds of materials are accordant with Ohm Theorem. The break sections of the tensile testing samples were scanned by electric microscope and the microstructures of the samples were studied. The electric conductive models were established for the two kinds of resin composites.In addition, the effects of carbon fiber content and elastic module on the volume resistivity of the carbon fiber reinforced resin composite were studied in this paper.