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CNT-PDMS 페인트 센서 표면 에칭에 따른 전기적 특성 분석
황희윤(Hui-Yun Hwang),정라희(La-Hee Jung) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
In this paper, we investigated the effect of wet-etching on the electrical characteristics of CNT-PDMS strain sensors. CNT-PDMS strain sensors consisted of MWCNTs and Polydemethylsyloxane according to the CNT wt%. For attaching metal electrodes on the strain sensor securely and decreasing the contact resistance, PDMS on the electrode area was removed by etching with NMP-TBAF solutions with respect to the etching duration. We fabricated the electrodes using sliver epoxy conducting adhesive and measured the electric resistance changes. Electrical conductivity increased as the MWCNT weight fraction and etching duration increased. Noticeable thing was that the electric conductivity of non-treated samples in log-scale increased order of 1 but those of etched samples increased order of 2 according to the CNT wt%. In addition, changes of electric conductivities from 2 to 3min of the etching duration were relatively small.
하중 속도가 유리섬유 에폭시 복합재료의 압전 특성에 미치는 영향
황희윤(Hui-Yun Hwang) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Recently, feasibility study of the damage monitoring for composite materials by the piezoelectric method was conducted, which was using the piezoelectric characteristics of polymeric materials for the matrix of composite materials. Form experimental results, it was concluded that the piezoelectric method can be useful nondestructive method for the damage monitoring of glass fiber epoxy composites. Piezoelectric properties of composites are basic properties for the analysis of the electro-mechanical coupling systems. Therefore, in this research, the effect of loading speed on the piezoelectric characteristics of glass fiber epoxy composites was investigated. Charge signals generated from composite specimens with three different fiber volume fractions under various loading speeds were measured experimentally. Experimental results show a significant decrease of the charge output by increasing the loading speed regardless of fiber volume fraction of glass fiber epoxy composites.
압전기법을 이용한 복합재료 손상모니터링의 가능성에 관한 연구
황희윤(Hui Yun Hwang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Since crack detection for laminated composites in-service is effective to improve the structural reliability of laminated composites, it have been tried to detect cracks of laminated composites by various nondestructive methods. An electric potential method is one of the widely used approaches for detection of cracks for carbon fiber composites, since the electric potential method adopts the electric conductive carbon fibers as reinforcements and sensors and the adoption of carbon fibers as sensors does not bring strength reduction induced by embedding sensors into the structures such as optical fibers. However, the application of the electric method is limited only to electrically conductive composite materials. Recently, a piezoelectric method using piezoelectric characteristics of epoxy adhesives has been successfully developed for the adhesive joints because it can monitor continuously the damage of adhesively bonded structures without producing any defects. Polymeric materials for the matrix of composite materials have piezoelectric characteristics similarly to adhesive materials, and the fracture of composite materials should lead to the fracture of polymeric matrix. Therefore, it seems to be valid that the piezoelectric method can be applied to monitoring the damage of composite materials. In this research, therefore, the feasibility study of the damage monitoring for composite materials by piezoelectric method was conducted. Using carbon fiber epoxy composite and glass fiber composite, charge output signals were measured and analyzed during the static and fatigue tests, and the effect of fiber materials on the damage monitoring of composite materials by the piezoelectric method was investigated.
황희윤(Hui Yun Hwang),김성영(Sungyoung Kim),김성현(Sunghyun Kim),임우동(Woodong Lim),조용환(Yonghwan Jo),한수호(Sooho Han) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
Recently, bicycle accident is increasing in proportion to the growth of bicycle riders due to interests of leisure sports. Speed wobbles on the smooth road and vibrations on the bumpy road during high-speed riding are main causes of bicycle accidents. We proposed improving method of handling stability for high-speed riding with a aerodynamic equipment similar to airfoils in order to prevent bicycle accidents caused by handle vibrations from uneven road. We designed airfoil-like structures which will be attached on the bicycle fork using numerical and experimental approaches. Designed equipment are installed on a road bike and tested on smooth and bumpy roads. We measured and compared accelerations on handle and fork of the road bike with and without the suggested equipment.