Electrical properties of different types of carbon fiber reinforced plastics (CFRPs) and hybrid CFRPs

The electrical resistance (ER)–time, current–voltage and ER–temperature behaviors of carbon fiber reinforced plastics (CFRPs) reinforced with high strength (HS), medium modulus (MM), and high modulus (HM) carbon fibers were studied. At the same time, the electrical properties of hybrid CFRPs (HCFRPs) reinforced with more than one type of carbon fibers were also studied. It was shown that the value of the current influences the electrical stability and the ER measurement accuracy. In order to obtain an accurate ER measurement, the current should be larger than 1.5 mA. All the CFRPs and HCFRPs are characterized by linear current–voltage and Ohmic behaviors. A negative temperature coefficient (NTC) behavior is exhibited for all types of specimens. The NTCs of the CFRPs reinforced with HS, MM and HM carbon fibers are 0.038, 0.033 and 0.094, respectively. For the specimens of HCFRPs containing HM carbon fibers, the NTC becomes larger with increasing the volume fraction of HM carbon fibers. The good linear and reversible relationship between the change in ER and temperature indicates that the CFRPs and HCFRPs may be used as temperature sensors.