Comparative study on piezoresistive properties of CFRP tendons prepared by two different methods

Abstract Carbon fiber reinforced polymer (CFRP) material is an exceptionally and light fiber-reinforced polymer that can be used as a smart sensor due to its remarkable piezoresistivity. This study presents a comparative study on piezoresistive characteristics of CFRP tendons manufactured by two different methods, i.e., the vacuum process method (VPM) and the brush process method (BPM). The tensile and resistance tests were conducted simultaneously on two groups of CFRP tendon specimens respectively by VPM and BPM to investigate their differences in initial resistances, piezoresistive performance and sensitivity. Test results showed that the initial resistance of the CFRP tendons prepared by the VPM is larger than those prepared by the BPM. The resistances of the CFRP tendon specimens by two methods increase uniformly with increasing strain. The resistance increases more quickly at the same strain increment for specimens prepared by BPM compared with those for VPM. Three stages can be observed according to the variation of fractional change in resistance (d R / R ) with tensile strain. The scope of d R / R varies from 0% to 55% for BPM specimens, which is much wider than that for VPM specimens, which fall within 8.5%. The result is that BPM specimens are more sensitive than that of VPM. The values of sensitivity ‘ K ’ obtained for BPM specimens varying from 22 to 28 are much bigger than that for VPM ranging from 2.7 to 3.5. For BPM specimens, the pre-tension process can tighten up the fibers to reduce crimp and significantly reduce the amounts of bubbles during the brush process. However, the specimens prepared by VPM without undergoing the pre-tension process showed a relative looser state and carbon fibers might crimp.