Strain and damage self-sensing properties of carbon nanofibers/carbon fiber–reinforced polymer laminates

Abstract

Unidirectional fiber-reinforced composites of ''plain'' carbon fiber-reinforced polymer laminates and carbon nanofibers modified carbon fiber-reinforced polymer laminates were prepared based on the manufacture of the epoxy resin modified with various contents of carbon nanofibers. The carbon nanofibers-modified epoxy matrix and carbon fiberreinforced polymer laminates specimens were subject to constant amplitude cyclic tensile loading, quasi-static tension loading, and incremental cyclic tension loading while the values of their electrical resistance were monitored through electrical resistance technique. Resistance-change curves of carbon nanofibers/carbon fiber-reinforced polymer laminates indicated the changes in conductive percolation networks formed by carbon fibers or carbon nanofibers. These changes can identify the complex damage modes and the loss of mechanical integrity in laminates. The changes in resistance of specimens showed a nearly linear correlation with the strain, so the damage process of the carbon fiberreinforced polymer laminates can be self-sensed according to the resistance-change curves. In addition, uniformly dispersed carbon nanofibers formed a network that spans the whole insulation area, which improved their self-sensing property of strain sensitivity without compromising the mechanical properties of the carbon fiber-reinforced polymer laminates. This technology can achieve the quantitative strain and damage self-sensing properties of nano-reinforced composites without any additional sensor, and it is bound to be a promising method for in situ health monitoring.

Properties and mechanisms of self-sensing carbon nanofibers/epoxy composites for structural health monitoring

“…rubber [8], epoxy [3], [9], [10], [11], [12], [13], [14], and cement [15], [16], [17], [18]) and electrically conductive reinforcement (e.g. carbon nanotubes [9], [12], [15], carbon nanofibers [3], [19], [20], graphene nanoplatelets [13], carbon black [10], [11], and nickel powder [21]). These composites are generally based on the use of conductive fillers, which create an electrical network whose resistance is dependent on the distance between fillers and the piezoresistivity of the fillers themselves [22].…”

“…If it is used as the matrix for the compressive strain sensors, it could not only eliminate the effects of humidity and polarization, but also enable the whole process monitoring of confined concrete structures subjected to compression. Compared to multiwall and single-wall carbon nanotubes, CNFs have relatively low cost, which is a favorable factor in practical engineering applications [20]. Therefore, it is worth to study the behaviors of epoxy-based composites containing CNFs to explore the possibility of using such nanocomposites as piezoresistive sensors for structural health monitoring.…”

Damage self-sensing behavior of carbon nanofiller reinforced polymer composites with different conductive network structures

“…The non-linear rate of resistivity increase at larger strains indicates a non-linear response for the number of conductive pathways (N) at large strain. This can be represented by Equation 7: (7) where M, W, U, V are constants.…”

“…At appropriate filler content, the resulting conductive polymer composites (CPCs) showed excellent electrical conductivities and considerable mechanical strength. These attributes were used to develop smart structural materials, including damage self-sensing (or damage self-monitoring) polymer composites able to provide structural and sensing properties [6][7][8]. The ability to detect damage in composite materials is extremely important and particularly in safety critical applications such as in the aerospace or automotive sectors.…”

Strain and damage self-sensing of basalt fiber reinforced polymer laminates fabricated with carbon nanofibers/epoxy composites under tension

“…Over the last decades, in-situ electrical resistance measurement (ERM) has been regarded as a nondestructive method for strain and damage sensing. Considerable numbers of researches have been performed to study the strain and damage monitoring of CFRP composites by using ERM [16], [17], [18], [19], [20]. For example, Wang et al [18], [20] studied the static/fatigue damage and dynamic strain monitoring in cross-ply CFRP composites by using direct current measurement techniques.…”