Sensing of dispersion and adhesion of PU type aircraft topcoat layer for LSP (Lightning Strike Protection) was evaluated by 2 dimensional (2D) electrical resistance (ER) mapping with different treatment times and multi-wall carbon nanotube (MWCNT) weight fractions. Conductive MWCNT was treated using hydrogen peroxide to improve dispersion in polyurethane (PU) type paint for several days. After treatment processing, MWCNT was dispersed in PU type coating solution using sonication dispersion method. CNT/PU coating solution was applied on the aircraft surface of carbon fiber reinforced epoxy composite (CFRC) using spray method. Static contact angle was performed using 4 types of solvents to calculate the work of adhesion between CNT/PU coating layer and CFRC surface. Surface ER of MWCNT added PU coating layer was measured to determine MWCNT dispersion. Visualization of MWCNT dispersion exhibited using 2-D ER mapping, whereas adhesion between MWCNT/PU coating layer and CFRC was evaluated via cross hatched cut test. The optimized condition of MWCNT treatment time and MWCNT weight fraction was found intensively.
The pencil lead drawing paper sensor (PLDPS) is a flexible and wearable sensing device, a new concept sensor that offers a tremendous potential feasibility for a variety of applications. Highly responsive, sensitive, low cost, easy-tohandle pencil lead graphite and paper made from cellulose pulp fibers extracted from wood, rags or grass, which are inexpensive, nature-friendly materials were used. The sensing effect on 3 different papers (Plane, Hwasun, and Han papers) based on the properties of PLDPS was compared via FT-IR, tensile test, optical observation and initial electrical resistance (ER). The interfacial and mechanical properties of epoxy and GF/epoxy composites were evaluated by damage sensing and ER mapping using PLDPS with impact, flexural, and interlaminar shear strength (ILSS) tests. The optimum type of paper used as the adherend for the pencil sensor was chosen as the plane paper. As glass fiber (GF)/epoxy composites were severely damaged, the large change in ER of PLDPS was observed distinctly.
Interfacial and mechanical properties of thermal aged carbon fiber reinforced epoxy composites (CFRP) were evaluated using acoustic emission (AE), electrical resistance (ER), contact angle (CA) and thermogram measurements. Unidirectional (UD)-composites were aged at 200, 300, and 400 °C to produce different interfacial conditions. The interfacial degradation was identified by Fourier transform infrared (FT-IR) spectroscopy after different thermal aging. AE and ER of UD composites were measured along 0, 30, 60 and 90 °. Changes in wavespeed, with thermal aging, were calculated using wave travel time from AE source to AE sensor and the changes in ER were measured. For a thermogram evaluation, the composites were laid upon on a hotplate and the increase in the surface temperature was measured. Static contact angle were measured after different thermal aging and elapsed times to evaluate wettability. Interlaminar shear Strength (ILSS) and tensile strength at transverse direction tests were also performed to explore the effects of thermal aging on mechanical and interfacial properties. While thermal aging of CFRPs was found to affect all these properties, the changes were particularly evident at 400 °C.
Evaluation of sensing for electrical conductive composites has been implemented using electrical conductive nano
materials such as graphene, CNT and carbon fiber. Electrical resistance (ER) measurement for nondestructive evaluation
(NDE) was developed using self-sensing composites because method of damage sensing and crack prediction of
composites under external load is possible to use at aerospace, heavy industry, and automobile. In this research, diverse
damage sensing from mechanical impact and thermal aging for electrical conductive composites was investigated by
using ER method. To have the test, electrical conductive materials such as graphene, CNT and carbon fiber and matrixes
such as epoxy and vinyl ester were used for damage sensing and finding optimum materials for improving the bonding
force. Two and three dimensional ER mapping was used to sense and predict damages from tensile, compressive, impact
and drilling force. The differences in ER from different force were compared to explore their usage for real time
monitoring and sensing of damages. Enhance optimum materials and conditions from diverse force were confirmed by
ER method.
Nano- and hetero-structures of modified carbon nanotube (CNT) and Graphene nano Platelet (GnP) can control significantly piezoresistive and optoelectronic properties in Microelectromechanical Systems (MEMS) as acoustic actuators. Interfacial durability and electrical properties of modified CNT and GnP embedded in poly (vinylidene fluoride) (PVDF) nanocomposites were investigated for use in acoustic actuator applications. Modified GnP coated PVDF nanocomposite exhibited better electrical conductivity than neat and modified CNT due to the unique electrical nature of GnP. Modified GnP coating also exhibited good acoustical properties. Contact angle, surface energy, work of adhesion, and spreading coefficient measurements were contributed to explore the interfacial adhesion durability between neat CNT or plasma treated CNT and plasma treated PVDF. Acoustic actuation performance of modified GnP coated PVDF nanocomposites were investigated for different radii of curvature and different coating conditions, using a sound level meter. Modified GnP can be a more appropriate acoustic actuator than CNT cases because of improved electrical properties. Optimum radius of curvature and coating thickness was also obtained for the most appropriate sound pressure level (SPL) performance. This study can provide manufacturing parameters of transparent sound actuators with good quality practically.
Nano- and hetero-structures of carbon nanotube (CNT), indium tin oxide (ITO), and Graphene nano Platelet (GnP) can control significantly piezoelectric and optoelectronic properties in Microelectromechanical Systems (MEMS) as acoustic actuators. Interfacial durability and electrical properties of CNT, ITO or GnP coated poly(vinylidene fluoride) (PVDF) nanocomposites were investigated for use in acoustic actuator applications. The GnP coated PVDF nanocomposite exhibited better electrical conductivity than either CNT or ITO, due to the unique electrical properties of GnP. GnP nanocomposite coatings also exhibited good acoustical properties. Contact angle, surface energy, work of adhesion, and spreading coefficient measurements were used to explore the interfacial adhesion durability between neat CNT (or plasma treated CNT) and plasma treated PVDF. The acoustic actuation performance of GnP coated PVDF nanocomposites were investigated for different radii of curvature and different coating conditions, using a sound level meter. GnP is considered to be a more appropriate acoustic actuator than either CNT or ITO because of its characteristic electrical properties. A radius of curvature of about 15 degrees was established as being most appropriate. Sound characteristics differed with varying coating thicknesses. The results of this study suggest that it should be possible to manufacture transparent actuators with good sound quality.
Transparent electrodes using carbon nanotube (CNT) have recently been studied as potential replacements for conventional indium tin oxide (ITO). In this work, CNT and ITO coated polyethylene terephthalate samples were prepared and studied. The degree of cohesion is dependent on the drying conditions. To explore affects of changing surface conditions, three drying temperatures, 20, 80, and 120°C, were used. Electrical resistance measurements were used to evaluate the interfacial durability and electrical properties of prepared transparent electrodes. A field emission scanning electron microscope was used to investigate surface changes and UV-spectroscopy was used to evaluate transparency as functions of the different drying temperatures. The electronic properties for these nanoparticle coated surfaces were evaluated using a cyclic voltametry method. Interfacial durability was evaluated by static contact angle measurement versus elapsed time. The pH values of the coatings were measured in a water solution. The durability of the CNT coated surfaces was found to be better than that of the ITO coated surfaces. The higher drying temperatures were found to produce better coated surfaces because of improved cohesion between the nanoparticles which resulted in improved electrical properties and improved durability.
Transparent electrodes using carbon nanotube (CNT) have recently been studied as potential replacements for
convention ITO. In this work, CNT or ITO coated polyethylene terephthalate (PET) samples were prepared and studied.
The degree of cohesion is dependent on the drying conditions. To explore effects of changing surface conditions, three
drying temperatures, 20 °C, 80 °C, and 120 °C, were used. Electrical resistance measures were used to evaluate the
interfacial durability and electrical properties of prepared transparent electrodes. FE-SEM was used to investigate surface
changes and UV-spectroscopy was used to evaluate transparency as functions of the different drying temperatures. The
electronic properties for these nanoparticle coated surfaces were evaluated using a cyclic voltametry method. Interfacial
durability was evaluated by static contact angle measurement changes with elapsed time. The pH values of the coatings
were measured in a water solution. The durability of the CNT coated surfaces was found to be better than that of the ITO
coated surfaces. The higher drying temperatures were found to produce better surfaces because of improved cohesion
between the nanoparticles which resulted in improved electrical properties and improved durability of the coated
surfaces.
Nano- and hetero-structures of carbon nanotube (CNT) and indium tin oxide (ITO) can control significantly piezoelectric
and optoelectronic properties in Microelectromechanical Systems (MEMS) as sensing and actuator under cyclic loading.
Optimized preparing conditions were obtained for multi-functional purpose of the specimen by obtaining the best
dispersion and turbidity in the solution. Optical transmittance and electrical properties were investigated for CNT and
ITO dipping and spraying coating on boro-silicate glass and polyethylene terephthalate (PET) substrates by electrical
resistance measurement under cyclic loading and wettability test. Uniform dip-coating was performed using Wilhelmy
plate method due to its simple and convenience. Spraying coating was applied to the specimen additionally. The change
in the electrical resistance and optical properties of coated layer were mainly dependent upon the number of dip-coating,
the concentration of CNT and ITO solutions, and the surface treatment condition. Electric properties of coating layers
were measured using four-point probe method, and surface resistance was calculated using a dual configuration method.
Optical transmittance of CNT and ITO coated PET film was also evaluated using UV spectrum. Surface energy and their
hydrophilic and hydrophobic properties of CNT and ITO coated substrates were investigated by wettability test via static
and dynamic contact angle measurements. As the elapsing time of cyclic loading passed, the stability of surface
resistance and thus comparative interfacial adhesion between coated layer and substrates was evaluated to compare the
thermodynamic work of adhesion, Wa. As dip-coating number increased, surface resistance of coated CNT decreased,
whereas the transmittance decreased step-by-step due to the thicker CNT and ITO networked layer. Nano- and heterostructural
effects of CNT and ITO solution on the optical and electrical effects have been studied continuously.
Self-sensing and dispersive evaluation were investigated with different dispersion solvents for single
carbon fiber/acid treated carbon nanotube (CNT)-epoxy composites by electro-micromechanical
technique and acoustic emission (AE) under cyclic loading/subsequent unloading. Gradient
nanocomposite specimen was used to obtain contact resistivity using two- and four-probe method.
Optimized dispersion procedure was set up to obtain improved mechanical and electrical properties. The
case using good dispersion solvent exhibited higher apparent modulus and lower electrical contact
resistivity for both the untreated and acid-treated CNT-epoxy composites. It is because of better stress
transferring effect and enhanced interfacial adhesion. Micro-damage sensing was also detected
simultaneously by AE combined with electrical resistance measurement. It exhibited the stepwise
increase with progressing fiber fracture due to the maintaining numerous electrical contacts of CNT. Thin
network of CNT by dipping method was formed on glass substrate to obtain conductive and transparent
plate by UV transmittance.
Self-sensing and actuation were investigated for carbon nanofiber (CNF) and Ni nanowire/polymer composites. Electro-micromechanical techniques can be used for evaluating self-sensing and interfacial properties indirectly under loading/subsequent unloading. Apparent modulus and contact resistivity for CNF/epoxy composites were evaluated as functions of different aspect ratio. CNF/epoxy composites with smaller aspect ratio shown to be higher apparent modulus due to high volume content in case of short aspect ratio. Surface energy via dynamic contact angle measurement was evaluated to obtain interfacial adhesion between nano-materials embedded matrix and carbon fiber sensor. Interfacial properties of CNF/epoxy with different aspect ratios were also obtained indirectly. CNF-PVDF, Ni nanowire-CNF-silicone and Ni nanowire-cellulose actuator were made successfully. Electrochemical actuator of CNF-PVDF was responded in electrolyte solution. Magnetic actuators of Ni nanowire-CNF-silicone and Ni nanowire-cellulose composites were monitored under electro-magnetic field with different frequency, wave function and voltage. Ni nanowire-CNF-silicone actuator with lightness and Ni nanowire-cellulose actuator with rapid frequency response having meaningful merits can be applied for various new smart structural materials.
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.
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.
Nondestructive damage sensing and load transfer mechanisms of thermal treated carbon nanotube (CNT) and nanofiber (CNF)/epoxy composites were investigated using electro-micromechanical technique. Carbon black (CB) was used only for the comparison. Electro-micromechanical techniques were applied to obtain the fiber damage and stress transferring effect of carbon nanocomposites with their contents. Thermal treatment and temperature affected on apparent modulus and electrical properties on nanocomposites due to enhanced inherent properties of each CNMs. Coefficient of variation (COV) of volumetric electrical resistance can be used to obtain the dispersion degree indirectly for various CNMs. Dispersion and surface modification are very important parameters to obtain improved mechanical and electrical properties of CNMs for multifunctional applications. Further optimized functionalization and dispersion conditions will be investigated for the following work continuously.
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