• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.150-153
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• 1996

Polyvinylidene fluoride(PVDF) thin films are fabricated by vapor deposition method and their dielectric characteristics are investigated. At electric field near 4MV/m, a phase transition occur with polar ${\alpha}$ . In accordance to increasing temperature, the dielectric relaxation of PVOF thin films show from 70Hz to 104Hz. This result correspond to Debye's theory[1]. Activation energy of PVDP thin film is 21Kca1/mo1.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.158-162
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• 2003

The PVDF(polyvinylidene fluoride) film sensor as one of smart sensors has good characteristics to detect the impact damages of composite structures. The capabilities of the PVDF film sensor for evaluating impact behaviors and damages of Gr/Ep laminates subjected to low-velocity impact were examined. From sensor signals, the specific wave-forms implying the damage were detected. The wavelet transform(WT) and Short Time Fourier Transform(STFT) were used to decompose the piezoelectric sensor signals in this study. The impact behaviors of Gr/Ep laminates were simulated and the impact forces were reconstructed using the sensor signals. Finally, the impact damages were predicted by finite element analysis with the reconstructed forces. For experimental verification, a series of low-velocity impact tests from low energy to damage-induced energy were carried-out. The extent of damage in each case was examined by means of ultrasonic C-scan and the measured damage areas were agreed well with the predicted areas by the F.E.A.

• 한국산학기술학회논문지
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• 제20권3호
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• pp.513-519
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• 2019

배수 시스템에서 오염퇴적물이 장기간 발생하게 되면 배수관 폐색현상을 일으켜 유지관리가 어렵고 배수관의 잔류수압이 커져 파손의 위험이 있다. 이에 본 연구에서는 PVDF 필름에 의해 발생하는 진동에너지를 활용하여 물리/화학적 폐색에 의한 터널배수 시스템 폐색을 감소시키는 시스템을 구축하였다. 또한, PVDF 필름을 기존 배수재와 융합한 하이브리드 배수재와 역압전 효과를 일으킬 수 있는 구동장치로 배수재 유지관리 시스템을 개발하였다. 터널 배수관 유지관리 성능을 고찰하기 위하여 실내조건에서 오염퇴적물을 모사하고 진동조건에서 폐색저감 효율을 관찰하였다. 그 결과 개발된 PVDF 필름 구동 장비로 20분 내외의 진동에너지를 발생하여 씻겨나간 오염퇴적물의 잔류면적을 측정한 결과 74.62%의 오염퇴적물 제거효과를 볼 수 있었다. 현장 적용성 평가를 위하여 PVDF 필름을 배수관에 부착하고 장기적으로 음압측정을 하여 실내실험으로부터의 측정 음압과 비교하여 현장실험의 대응율을 제시하였다. 현장실험은 터널 배수관으로부터 내부에 폐색이 주로 발생하는 구간인 종배수관과 횡배수관에 PVDF 필름을 부착하였고 터널현장 음압측정 실험으로부터 오염물퇴적 제거효율은 실내실험대비 현장 대응율은 90% 이상으로 확인됐다.

• Composites Research
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• 제15권5호
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• pp.7-13
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• 2002

압전필름센서는 복합재 구조물의 저속충격응답을 관측하기에 우수한 특성을 지니고 있다. 본 연구에서는 Gr/Ep 복합재 적층판이 손상이 발생할 수 있을 정도의 충격에너지를 받았을 때 압전필름센서 신호를 이용하여 충격거동을 모니터링할 수 있는 가능성에 대하여 고찰하였다. 손상이 발생하지 않는 저에너지 충격조건부터 국부적인 손상을 유발할 수 있는 충격조건까지 압전필름센서가 부착된 Gr/Ep 복합재 적층판에 대하여 16가지의 저속충격시험을 수행하였다. 세 가지 조거의 충격시험에서 기지균열 및 층간분리 등의 국부적인 손상이 발생하였으나, 충격력과, 변위, 변형률, 압전센서 신호와의 관계를 이용한 선형해석 모델을 사용하여 충격하중에 의한 복합재 적층판의 응답을 예측하는 정방향 문제와 압전센서 신호로부터 충격력을 복원하는 역방향 문제에서 시험과 해석 결과는 비교적 잘 일치하는 경향을 보였다. 복원된 충격력으로부터 국부적인 손상이 발생할 정도의 충격까지는 압전필름센서 신호를 이용하여 충격력을 정확히 복원할 수 있음을 확인하였다.

• 소음진동
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• 제8권4호
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• pp.632-642
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• 1998

A method based on finite element discretization is developed for optimizing the polarization profile of PVDF film to create the modal transducer for specific modes. Using this concept, one can design the modal transducer in two-dimensional structure having arbitrary geometry and boundary conditions. As a practical means for implementing this polarization profile without repoling the PVDF film the polarization profile is approximated by optimizing electrode patterns, lamination angles, and poling directions of the multi-layered PVDF transducer. This corresponds to the approximation of a continuous function using discrete values. The electrode pattern of each PVDF layer is optimized by deciding the electrode of each finite element to be used or not. Genetic algorithm, suitable for discrete problems, is used as an optimization scheme. For the optimization of each layers lamination angle, the continuous lamination angle is encoded into discrete value using binary 5 bit string. For the experimental demonstration, a modal sensor for first and second modes of cantilevered composite plate is designed using two layers of PVDF films. The actuator is designed based on the criterion of minimizing the system energy in the control modes under a given initial condition. Experimental results show that the signals from residual modes are successfully reduced using the optimized multi-layered PVDF sensor. Using discrete LQG control law, the modal peaks of first and second modes are reduced in the amount of 12 dB and 4 dB, resepctively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1190-1192
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• 1995

Poly(vinylidene fluoride)(PVDF) is one of the most studied polymers in the latest date. The interest in PVDF lies in its remarkable piezoelectric and pyroelectric properties. Also, PVDF has at least four known crystalline structures(; they are referred to as the ${\alpha},\;{\beta},\;{\gamma}\;and\;{\alpha}_p$ phase or forms II, I, III and $IV_p$). In this study, the manufactured PVDF thin film through vapor deposition method had form II(; the glass at $70^{\circ}C$). This thin film was investigated by x-ray diffraction(XRD), Fourier Transform Infrared(FT-IR) spectroscopy and Differential Thermal Analysis(DTA). XRD and FT-IR indicate crystallization forms from the glass at $70^{\circ}C$ into form II.

• 한국전기전자재료학회논문지
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• 제21권10호
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• pp.923-929
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• 2008

On the piezoelectric polymer, PVDF (poly vinylidene fluoride), the transparent conducting oxide (TCO) electrode material thin film was deposited by roll to roll sputtering process mentioned as a mass product-friendly process for display application. The deposition method for ITO Indium Tin Oxides) as our TCO was DC magnetron sputtering optimized for polymer substrate with the low process temperature. As a result, a high transparent and good conductive ITO/PVDF film was prepared. During the process, especially, the gas mixture ratio of Ar and Oxygen was concluded as an important factor for determining the film's physical properties. There were the optimum ranges for process conditions of mixture gas ratio for ITO/PVDF From these results, the doping mechanism between the oxygen atom and the metal element, Indium or Tin was highly influenced by oxygen partial pressure condition during the deposition process at ambient temperature, which gives the conductivity to oxide electrode, as generally accepted. With our studies, the process windows of TCO for display and other application can be expected.

• E2M - 전기 전자와 첨단 소재
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• 제2권2호
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• pp.127-136
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• 1989

PVDF 필름의 압전성과 결정구조와의 관계를 조사하기 위하여 X선 회절과 압전계수를 측정하였다. 코로나 분극처리된 PVDF의 압전계수는 분극전압에 비례하여 증가하고 결정구조도 .alpha.형, 극성.alpha.형, .betha.형의 순으로 변화하였다. 이와같은 결과로부터 PVDF의 압전특성은 결정영역내의 쌍극자 배향에 의한 결정구조변화에 기인됨을 알 수 있었다.

• International Journal of Internet, Broadcasting and Communication
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• 제6권1호
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• pp.13-15
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• 2014

We develop a method to fabricate a flexible thin film audio systems using polyvinylidene fluoride(PVDF). The system we designed showed the properties of increased flexibility, transparency, and sound pressure levels. As an input port of two terminals, transparent oxide thin film with a low resistivity is adopted. In order to provide dielectric insulation, a transparent insulating oxide thin film is coated to obtain double-layered structure. In the range of visible light, the output from the output of the system showed a increased and improved sound pressure level. The piezoelectric polymer film of PVDF is used to produce mechanical vibration due to the applied electrical voltage signal. An analog electric voltage signal is transformed into sound waves in the audio system.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.40-41
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• 2006

In this work, we developed the 0-3 type piezoelectric composite to incorporate the advantages of both ceramic and polymer. The PVDF-PZT composites were fabricated with various mixing ratio by 3-roll mi11 mixer. The composite solutions were coated on ITO bottom-electrode deposited on PET (polyethylene terephthalate) polymer film by the conventional screen-printing method. After depositing the top-electrode of silver-paste, 4kV/mm of DC field was applied at $120^{\circ}C$ for 30min to poling the 0-3 composite film. The value of $d_{33}$ was increased as the PZT weight percent was increases. But the $g_{33}$ value showed the maximum at 65 wt% of PZT powder.