Nondestructive damage sensing and load transfer mechanisms of carbon nanotube (CNT), nanofiber (CNF), and Ni nanowire strands/epoxy composites were investigated using electro-micromechanical technique. Electrospun PVDF nanofiber was also prepared as a piezoelectric sensor. High volume% CNT/epoxy composites showed significantly higher tensile properties than neat and low volume% CNT/epoxy composites. CNF /epoxy composites with smaller aspect ratio showed higher apparent modulus due to high volume content in case of shorter aspect ratio. Using Ni nanowire strands/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 strands with different type and content/epoxy composites were indirectly measured apparent modulus using uniformed cyclic loading and electro-pullout test. CNT or Ni nanowire strands/epoxy composites showed humidity and temperature sensing within limited ranges, 20 vol% reinforcement. Thermal treated electrospun PVDF nanofiber showed higher mechanical properties than the untreated case due to increased crystallization, whereas load sensing decreased in heat treated case. Electrospun PVDF nanofiber web also responded the sensing effect on humidity and temperature. Nanocomposites using CNT, CNF, Ni nanowire strands, and electrospun PVDF nanofiber web can be applicable practically for multifunctional applications nondestructively.
Several conductive nanomaterials are investigated for structural electrically conductive adhesive applications, including carbon nanofibers and nickel nanostrands. The suitability of nanostrands as a conductive filler is reviewed. Adhesive formulations based on Hysol 9396 epoxy are tested for electrical and structural properties. Several formulations are found to be capable of providing enhanced adhesive strength while affording excellent electrical conductivity. The development of full strength structural conductive adhesives can enable a wide range of applications where the strength of current commercially available electrically conductive adhesive systems is a limiting factor. Superior conductivity results are obtained by the nickel nanomaterials, with milliohm gap resistance and resistivity on the order of 10−2 Ω cm possible at loading of 5 vol%. Initial results indicate that these systems present good survivability in thermal cycling conditions.
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.
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