Interfacial Evaluation and Self-Sensing of Single Micro-Carbon Fiber/CNF–Brittle-Cement Composites using Electro-Micromechanical Tests and Acoustic Emission

Abstract

Interfacial evaluation and self-sensing were investigated for single carbon fiber/carbon nanofiber (CNF)-brittle-cement composites by electro-micromechanical techniques and acoustic emission (AE) under cyclic loading/subsequent unloading. During the curing process, the volumetric resistivity decreased dramatically, during the initial stage, due to increased contact points between the cement matrix and the CNF. The apparent modulus and electrical contact resistivity of micro-carbon fiber/CNF-cement composites were also evaluated as a function of CNF concentration. As the CNF concentration increased, the maximum stress increased, whereas the change in resistance ρ decreased gradually and the contact resistivity sensitivity increased as well. Micro-damage sensing of micro-carbon fiber/CNF-cement composites was also investigated by electrical resistivity and AE. When the first fracture of micro-carbon fiber occurred, the electrical resistivity increased 'infinitely' with increasing lower CNF concentrations. For high 5 wt% CNF, however, the fracture of micro-carbon fiber could be detected just in one large step increment change in the electrical resistivity as well as consistent AE events. The percolation structure of CNF is not well formed in the cement matrix due to relatively-low electrical conductivity. The chosen CNF-cement composites are not suitable for conductive and sensing applications because of their many vertical microcracks.

Piezoelectricity-based self-sensing of compressive and flexural stress in cement-based materials without admixture requirement and without poling

“…Self-sensing by electrical resistance measurement has been reported in cement-based materials that have been rendered electrically conductive by the use of electrically conductive admixtures, such as steel fibers [7,8], carbon fibers [9][10][11][12][13][14][15], carbon nanotubes [16][17][18][19][20][21][22][23][24][25][26][27][28], carbon nanofibers [29,30], graphite nanoplatelets [16,31] and carbon black [28,[32][33][34]. Without the conductive additive, the cement-based material tends to be too high in the electrical resistivity for the resistance of a large volume of a cement-based structure to be effectively measured.…”

Detection of damage in cylindrical parts of carbon fiber/epoxy composites using electrical resistance (ER) measurements

“…Hyperbolic quadric relationships between the tensile load and the electrical resistance have been reported [22][23][24]. It was observe to depend upon interfacial properties between CF and M A N U S C R I P T A C C E P T E D In the study reported here, unlikely conventional FBG sensor or strain gauge methods, ER measurements were used for detection of cracking and crack propagation during flexural loading of short CFRP cylinders (e.g.…”

A Review on the Applications of Nanofluids in Cement Industry

“…Fibers can be incorporated into the cemented matrix to overcome these shortcomings [7]. The development of new nanosized fibers that can act as bridges across cracks and voids has opened a new field for nanosized reinforcement in concrete [8]. Carbon nanotubes (CNTs) are considered as one of the most advantageous nanomaterials for reinforcement purposes.…”