• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.535-540
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• 2013

In this work, active control algorithm is adopted to reduce delamination effects of the damaged composite structure and control performance with MFC actuator is numerically evaluated. Finite element model for the damaged composite structure with piezoelectric actuator is established based on improved layerwise theory. In order to achieve high control performance, MFC actuator, which has increased actuating force, is considered as a piezoelectric actuator. Mode shapes and corresponding natural frequencies for the damaged smart composite structure are studied. After design and implementation of active controller, dynamic characteristics of the damaged smart composite structure are investigated.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.216-219
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• 2002

Conventional piezoelectric lead-zirconate-titanate (PZT) senor has high sensitivity, but it is very brittle. Recently polymer films such as polyvinylidene fluoride (PVDF) have been used use as a sensor. The advantages of PVDF are the flexibility and mechanical toughness. Simple process and possible several shapes are also additional advantages. PVDF sensor can be directly embedded and attached to a structure. In this study, PVDF sensor was embedded in single glass fiber/epoxy composites whereas PZT sensor with AE was attached to single fiber composites (SFC). Piezoelectric sensor responds to interfacial damage of SFC. The signals measured by PVDF sensor were compared to PZT sensor. PZT sensor detected the signals of fiber fracture, matrix crack, interfacial debonding and even sensor delamination, whereas PVDF sensor only detected fiber fracture signals so far, because PZT sensor is much more sensitive than current PVDF sensor. Wave voltage of fiber fracture measured by PVDF sensor was lower than that of PZT sensor, but the results of fast Fourier transform (FFT) analysis were same. Wave velocity using two PZT sensors was also studied to know the internal and surface damage effect of epoxy specimens.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.126.1-126.1
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• 2005

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.103-104
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• 2006

• Structural Engineering and Mechanics
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• 제62권3호
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• pp.325-344
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• 2017

The present paper investigates the propagation of Love-type wave in a composite structure comprised of imperfectly bonded piezoelectric layer with lower fiber-reinforced half-space with rectangular shaped irregularity at the common interface. Closed-form expression of phase velocity of Love-type wave propagating in the composite structure has been deduced analytically for electrically open and short conditions. Some special cases of the problem have also been studied. It has been found that the obtained results are in well-agreement to the Classical Love wave equation. Significant effects of various parameters viz. irregularity parameter, flexibility imperfectness parameter and viscoelastic imperfectness parameter associated with complex common interface, dielectric constant and piezoelectric coefficient on phase velocity of Love-type wave has been reported. Numerical computations and graphical illustrations have been carried out to demonstrate the deduced results for various cases. Moreover, comparative study has been performed to unravel the effects of the presence of reinforcement and piezoelectricity in the composite structure and also to analyze the existence of irregularity and imperfectness at the common interface of composite structure in context of the present problem which serves as a salient feature of the present study.

• Smart Structures and Systems
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• 제13권4호
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• pp.567-585
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• 2014

The piezoelectric transverse $d_{15}$ shear sensing mechanism is firstly assessed experimentally for a cantilever smart sandwich plate made of a piezoceramic axially poled patched core and glass fiber reinforced polymer composite faces. Different electrical connections are tested for the assessment of the sensor performance under a varying amplitude harmonic (at 24 Hz) force. Also, the dynamic response of the smart sandwich composite structure is monitored using different acquisition devices. The obtained experimentally sensed voltages are compared to those resulting from the benchmark three-dimensional piezoelectric coupled finite element simulations using a commercial code where realistic features, like equipotential conditions on the patches' electrodes and mechanical updating of the clamp, are considered. Numerically, it is found that the stiffness of the clamp, which is much softer than the ideal one, has an enormous influence on the sensed voltage of its adjacent patch; therefore, sensing with the patch on the free side would be more advantageous for a cantilever configuration. Apart from confirming the latter result, the plate benchmark experimental assessment showed that the parallel connection of its two oppositely poled patches has a moderate performance but better than the clamp side patch acting as an individual sensor.

• 센서학회지
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• 제17권3호
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• pp.162-167
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• 2008

In this paper we report on the electrical properties of carbon fiber which is an attractive material for strain gauges and can also be applied to resonating micro sensors. The carbon fibers used in this research was manufactured from polyactylonitrile (PAN). The fabricated carbon fibers had about $10\;{\mu}m$ in length and several centimeters in length. We employed a micro structure to measure electrical properties of the carbon fiber. The measured electrical resistivity of the carbon fibers were about $3{\times}10^{-3}{\Omega}{\cdot}cm$ A gauge factor of the carbon fiber is also observed with the same system and it was about 400, depending on the structure of the carbon fiber. For the sensor applications of the carbon fiber, it is selectively placed between the gap of Al electrodes using a dielectrophoresis method. When the carbon fiber is resonated by a piezoelectric ceramic, resistance change at a variety of resonance mode was observed through an electrical system.

• 한국통신학회논문지
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• 제17권10호
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• pp.1092-1099
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• 1992

본 논문은 광섬유 가속도기를 이용한 중력가속도$(0{\sim}1G)$의 감도를 보였다. 단일모드 광섬유 Mach-Zehnder 간섭계가 약 1 그람 정도의 probe mass를 이용하여 광섬유 내의 스트레인에 의해 발생된 광로정 변화를 감지하는데 이용 되었다. 본 시스템의 기준 통로내 PZT 원통의 위상 변환 이득은 0.88rad./v로 측정 되었다.

• 한국산업융합학회 논문집
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• 제23권6_2호
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• pp.943-948
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• 2020

In this paper, we developed a fiber optic interferometer system based on frequency-swept laser. This frequency-swept laser with an external-cavity structure can generate a high coherent light with a linewidth of 132 kHz at 1552 nm. It also shows a superior swept linearity of R2 = 0.99995 under repetition rate of 200 kHz due to absence of mechanical moving parts in the laser cavity. By using a piezoelectric fiber optic stretcher, various vibration experiments were implemented, such as 0.5 to 2.0 kHz vibration signals with intervals of 0.5 kHz, with a sampling rate of 7 kHz. Real-time peak tracking can be successfully recovered according to the applied vibration frequency with high linearity of R2 = 0.99983.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 춘계총회,특별강연,심포지움,연구발표회
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• pp.151.1-151.1
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• 2000