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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.

Self-sensing and interfacial evaluation were investigated with different dispersion solvents for single carbon fiber/carbon nanotube (CNT)-epoxy composites by electro-micromechanical technique and acoustic emission (AE) under loading/subsequent unloading. Optimized dispersion procedure was set up to obtain improved mechanical and electrical properties. Apparent modulus and electrical contact resistivity for CNT-epoxy composites were correlated with different dispersion solvents for CNT. CNT-epoxy composites using good dispersion solvent showed higher apparent modulus because of better stress transferring effect due to relatively uniform dispersion of CNT in epoxy and enhanced interfacial adhesion between CNT and epoxy matrix. However, good solvent showed high apparent modulus but low thermodynamic work of adhesion, Wa for single carbon microfiber/CNT-epoxy composite. It is because hydrophobic high advanced contact angle was shown in good solvent, which can not be compatible with carbon microfiber well. Damage sensing was also detected simultaneously by AE combined with electrical resistance measurement. Electrical resistivity increased stepwise with progressing fiber fracture due to the maintaining numerous electrical contact by CNT.

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Self-sensing and actuation were investigated for CNF and Ni nanowire/epoxy and silicone composites. Electro-micromechanical techniques can be used for self sensing for loading, temperature. CNF/epoxy composites with smaller aspect ratio showed higher apparent modulus due to high volume content in case of shorter aspect ratio. Apparent modulus and electrical resistivity change were evaluated as functions of different carbon fiber types. Interfacial properties of CNF/epoxy with different aspect ratios were obtained indirectly. Using Ni nanowire/silicone composites with different content, load sensing response of electrical contact resistivity was investigated under tensile and compression condition. The mechanical properties of Ni nanowire with different type and content/epoxy composites were indirectly measured apparent modulus using uniformed cyclic loading and electro-pullout test. Ni nanowire /epoxy composites showed temperature sensing within limited ranges, 20 vol% reinforcement. CNF-PVDF and Ni-silicone actuator were made successfully. Electrochemical actuator of CNF-PVDF was responded in electrolyte solution. Magnetic actuator of Ni nanowire-silicone composites was monitored under electro-magnetic field. CNF-Ni nanowire-silicone actuator having meaningful merits can be expected to be new smart structural materials at a various applications. Nanocomposites using CNF and Ni nanowire can be applicable practically for multi-functional applications nondestructively.