• Composites Research
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• v.17 no.5
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• pp.7-14
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• 2004

This paper deals with adaptive fuzzy logic controller design to achieve proper dynamic response of a composite thin-walled beam with a tip mass. In order to check the effectiveness of this controller, three different types of control logic are selected and applied. The adaptive control capabilities provided by a system of piezoactuators bonded or embedded into the structure are also implemented in the system. Results show that the fuzzy logic controller is more effective than the proportional or velocity feedback controller for the vibration control of composite thin-walled beam with a tip mass.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.358-359
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• 2006

Ru-C nano-composite films were prepared by MOCVD, and their microstructures and their electrode properties for oxygen gas sensors were investigated. Deposited films contained Ru particles of 5-20 nm in diameter dispersed in amorphous C matrix. The AC conductivities associating to the interface charge transfer between Ru-C composite electrode and YSZ electrolyte were 100-1000 times higher than that of conventional paste-Pt electrodes. The emf values of the oxygen gas concentration cell constructed from the nano-composite electrodes and YSZ electrolyte showed the Nernstian theoretical values at low temperatures around 500 K. The response time of the concentration cell was 900 s at 500 K.

• Journal of the Korean Society of Safety
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• v.18 no.3
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• pp.101-108
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• 2003

Polymeric positive temperature coefficient(PTC) composites have been prepared by incorporating carbon black(CB) into high density polyethylene(HDPE), polyphenylene sulfide(PPS) and polybutylene terephthalate(PBT) matrices. A PTC effect was observed in the composite, caused by the large thermal expansion due to He consecutive melting of HDPE, PPS and PBT crystallites. This theory is based upon the premise that the PTC phenomenon is due to a critical separation distance between carbon particles in the polymer matrix at the higher temperature. The influence of PTC characteristics of the PPS/CB composite can be explained by DSC result. HDPE, one of prepared composition, exhibit the higher performance PTC behavior that decreaseing of negative temperature coefficient(NTC) effect and improved reproducibility by chemically crosslinking. Also, PBT/CB and PPS/CB composites exhibit the higher PTC peack temperature than HDPE/CB PTC composite, individually $200^{\circ}C$ and $230^{\circ}C$. These PTC composite put to good use in a number of safety application, such as self$.$controlled heater, over-current protectors, auto resettable switch, high temperature proctection sensor, etc.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.9-10
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• 2012

Efficient operation of construction equipment has become more and more important in the competitive construction environment. Accurate measurement of performance rate of construction equipment is a critical factor for a construction project planning. However, it might be quite difficult to measure the performance rate due to diverse practical limitations such as continuously variable performance rate of construction equipment, considerable indirect cost, large construction field, and so on. Therefore, the purpose of this paper is to propose an automatic algorithm that measures a performance rate of construction equipment with a multipurpose composite sensor. It is expected that the algorithm compiles database on construction equipment and in advance, facilitates efficient operation of construction equipment.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.25-28
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• 2005

The optical fiber is known for the proper sensor which can accomplish the structural health monitoring, Fiber Bragg Grating sensors are being studied more than any other fiber optic sensors due to good multiplexing capabilities. But because the signal stability of FBG sensors can be influenced by the strain gradient, it needs to analyze signal of FBG sensors. Particularly acoording to strain gradient induced by structural geometry or cracks, the spectrum peak of the FBG sensor signal can be split easily. In this paper, the spectrum analysis of the FBG sensor signal was performed and the region of embedment of FBG sensors was determined in $H_2$ pressure vessel by numerical method.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.2
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• pp.146-151
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• 2013

Carbon nanofibers (CNFs) are electrically conductive. When CNFs are used as fillers in resin, this electrical conductivity can be yielded without adversely affecting the mechanical properties of the resin. When an elastomer is adopted as the resin, a conductive elastomer can then be produced. Due to its flexibility and conductive properties, a large strain sensor based on changes in resistivity may be produced, for strain sensing in flexible structures. In this study, a patch-type large strain sensor using resistivity change in a CNF/elastomer composite was proposed. The measurement limits of the sensor were investigated experimentally, and the limit was found to be 40%, which greatly exceeded the limits of conventional metal-foiled strain gages. Also, the proposed CNF/elastomer large strain sensor can be used to measure flexible materials, while conventional strain gages cannot be used to measure such strains.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.161-164
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• 2002

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity impacts. Tensile test was performed with the measurement of optical signal and acoustic emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated by wavelet transform. EFPI was less sensible to the damage signals compared with the optical fiber vibration sensor. It was found that damage information of comparable in quality to acoustic emission data could be obtained from the optical fiber vibration sensor signals.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.154-157
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• 2003

Precision displacement of less than a few nm resolution was measured in real-time using fiber optic EFPI sensor. The novel method for real-time processing of analyzing EFPI output signal was developed and verified. Linearity in the mean values of interferometric light intensity among adjacent fringes was shown, and the sinusoidal approximation algorithm that estimates past and coming fringe values was verified through the linearity. Real-time signal processing program was developed, and the intensity signal of the EFPI sensor was transformed to the phase shift with this program. The resolution below 0.4 ~ 10 nm in the displacement range of $0 ~ 300\mu\textrm{m}$ was obtained by reducing the photodetector noise using low-pass filter and signal averaging. The nano-translation stage with a Piezo-electric actuator and the EFPI sensor system was designed and tested. This stage successfully reached to the desired destination in $15\mu\textrm{m}$ range within 1 nm accuracy.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.119-122
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• 2004

A CPGFRP(Carbon Powder Glass Fiber Reinforced Plastics) sensor was fabricated for fine crack detection of structures. The electrical resistance of the sensor was measured on condition of various composition of carbon powders and thickness of bundle of glass fibers. The resistance was decreased as the increase of the content of carbon powders and the TEX of the glass fibers. In the case of loading on CPGFRP sensor, because inner crack was propagated, the part of percolation structures was disconnected. The sensor is superior to carbon fiber for the detecting ability of fine crack.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.613-619
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• 2006

This paper introduces a new structural health monitoring using a nano sensor. The sensor is made of nano smart composite material based on carbon nanotubes. The nano sensor is fabricated as a thin and narrow polymer film sensor that is bonded or deposited onto a structure. The electrochemical impedance and dynamic strain response of the neuron change due to deterioration of the structure where the sensor is located. A network of the long nano sensorcan form a structural neural system to provide large area coverage and an assurance of the operational health of a structure without the need for actuators and complex wave propagation analyses that are used with other methods.