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3차원 2-Step Braided 복합재료의 탄성 계수 예측
변준형,Byun, Joon-Hyung 한국기계연구원 1993 硏究論文集 Vol.23 No.-
In order to acquire more comprehensive understanding of textile composites, the processing-microstructure-performance relationships for a variety of material systems, reinforcing schemes and processing technologies should be established. In this paper, emphasis is placed on the integrated analysis of three-dimensional (3-D) 2-step braided composites. The analysis includes the geometric model of unit cells, identification of key process parameters and processing windows due to limiting geometries of yarn jamming, and prediction of elastic constants of the composite. The coordinate transformation and averaging of stiffness and compliance constants are utilized in the prediction of elastic constants. Since there are several types of unit cells in the thickness and width directions of the composites, characterization of mechanical properties is based upon the macro-cell, which occupies the entire cross-section and the unit pitch length of the sample. The performance map demonstrates that a wide range of elastic properties can be achieved by varying the geometric and process parameters.
레이저 유도 초음파를 이용한 복합재료 층간 결함의 비접촉 비파괴 평가
이승준(Seung-Joon Lee),하영준(Young-Joon Ha),이준현(Joon-Hyun Lee),변준형(Joon-Hyung Byun) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
The objective of this research is to develop non-contact and real time inspection technique based on laser generated ultrasound to evaluate delamination in CFRP composite fabricated from recently developed 3-dimensional fiber placement system. In this study, a hybrid laser generation/air-coupled detection ultrasonic system is presented. Fiberized Nd:YAG pulse laser with line array slit is used to generate ultrasonic guided wave in unidirectional CFRP specimen with artificial delamination. In order to investigate the reception ability of ultrasonic guided wave propagated through the area of delamination air-coupled transducer is used as reception of guided wave. The characteristic of time domain waveform and frequency spectrum of guided wave received from air-coupled transducer based on non-contact scheme is discussed. By scanning over the surface beneath which a delamination lies, it is possible to achieve 2-dimensional image and measure the size of delamination.
하영준(Young-Joon Ha),이승준(Seung-Joon Lee),이준현(Joon-Hyun Lee),변준형(Joon-Hyung Byun) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.6
Carbon fibre reinforced plastics (CFRP) should be inspected in fabrication process in order to enhance quality by prevent defects such as delamination and void. Generally, ultrasonic technique is widely used to evaluate FRP. In conventional ultrasonic technique, transducer should be contacted on FRP. However, conventional contacting method could not be applied in fabrication process and novel non-contact evaluating technique was required. Technique using air-coupled transducer can make non-contacting ultrasonic technique available in evaluation of FRP. Therefore, in this study, generation technique of laser-based ultrasound using Nd:YAG pulse laser(532㎚, 32mJ) system and reception technique using air-coupled transducer are applied for the non-destructive and non-contact evaluation of delamination in CFRP. Wave propagating through artificial delamination region was received using pitch-catch arrangement. Signal characteristics due to defects were analyzed to find a factor for detecting defects. PZT sensor was used to get a trend of waveform and fundamental database. The high frequency component of 1.1 ㎒ of laser-generated guided wave received with piezoelectric sensor disappeared after propagating through delamination region. However, it could not be received this high frequency guided wave by using air-coupled transducer and linear slit array. In a frequency spectrum of laser-generated guided wave received by air-coulped transducer, the first peak of frequency spectrum under 100㎑ received in the defect region showed higher than in the sound region. The peak of frequency spectrum represented approvable parameter to detect delamination in CFRP. By using this feature, line scanning data was acquired in fully non-contacting pitch-catch method and was proved as useful technique for detecting delamination in CFRP.
이상갑,변준형,백부근,현범수,Lee, Sang-Gab,Byun, Joon-Hyung,Paik, Bu-Geun,Hyun, Beom-Soo 대한조선학회 2009 大韓造船學會 論文集 Vol.46 No.6
The researches on the development of composite material underwater vehicle propeller have been actively attempted for the reduction of radiation noise with outstanding damping effects. Composite material propellers have almost been designed and produced by the foreign experts, and it is difficult to obtain the related informations about their flow, vibration, material characteristics because they are treated as the secrets with close relationship to the military technology, especially in the case of underwater vehicles. For the security of domestic manufacture of composite material propeller and the comparison and examination of its performance and radiation noise characteristics with those of German CONTUR composite material propeller, two propellers were self-produced according to the fiber weaving and array using compressible molding process and their self performances and radiation noise characteristics were measured. The mean fluctuations of blade tip of self-produced composite material propeller were increased and the radiation noises in the low frequency band were reduced compared to those of CONTUR, which could be estimated as the change of material characteristics and also be thought to be used for the future research informations.
3차원 프리폼 T-빔 구조물의 개발을 위한 적층복합재료 섬유비율의 최적화
이동우,김창욱,변준형,송정일,Lee, Dong-Woo,Kim, Chang-Uk,Byun, Joon-Hyung,Song, Jung-Il 한국복합재료학회 2017 Composites research Vol.30 No.5
본 연구에서는 적층복합재료에 발생하는 주요 손상인 박리를 방지하기 위하여, 굽힘-비틀림 하중이 작용하는 T-빔의 유한요소해석을 수행하였다. 복합재료 T-빔의 제작에 사용할 수 있는 3차원 직조 프리폼을 설계하고자 하였으며, 이는 2차원 구조의 직조섬유가 두께방향으로도 직조가 되어 있는 형태로서, 층간 분리에 의한 박리를 방지할 수 있는 구조이다. 적층복합재료의 해석 및 평가를 위하여 개발된 유한요소해석 소프트웨어인 ANSYS Composites PrePost를 이용하여 구조해석을 수행함으로써 적층복합재료의 섬유비율을 최적화하고, 이를 토대로 3차원 프리폼 T-빔의 제작을 위한 가이드라인을 제시하였다. 해석결과, T-빔의 길이방향 섬유의 비율이 수직방향 섬유의 2배일 때 가장 높은 강도를 보였으며, 하중조건의 변화에도 최적화된 빔 구조의 강도가 유지되는 것을 확인할 수 있었다. 도출된 섬유비율을 이용하여 3차원 프리폼을 개발할 경우, 박리가 일어나지 않는 고강도의 T-빔 구조물을 제작할 수 있을 것으로 기대된다. Finite element analysis of T-beam laminate structure under bending-torsional loading was conducted to prevent the delamination which is the major failure behavior on laminated composites. Three-dimensional preform, which is that fabric is braided through thickness direction, is suggested from the laminate analysis. The analysis aimed to optimize the fiber ratio in laminated composites. After it is suggested that guideline for design of T-beam structure using commercial software ANSYS Composites PrePost. The results show that strength of T-beam structure is increased 21.6% when the fiber density along with beam length direction is two times bigger than transverse direction. It is expected that development of high strength T-beam structure using designed three-dimensional preform.