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복합재 항공기 전기체 구조시험 시험하중 산출 방법 연구
최익현(Ik-Hyeon Choi),안석민(Seok-Min Ahn) 한국항공우주연구원 2011 항공우주기술 Vol.10 No.2
복합재 항공기의 설계하중 데이터로부터 전기체 구조시험 중에 하중부가용 스트랩에 부가될 시험하중의 크기를 산출하는 몇 가지 방법에 대하여 비교 분석하였다. 이 방법들을 KC-100 복합재 항공기 좌측 주익의 시험하중 산출과정에 적용해보고 산출된 결과의 특성 및 차이를 분석하였다. 항공기 전기체 구조시험에 부가되는 시험하중은 각 항공기의 설계하중의 특성 및 하중부가용 스트랩의 위치 등에 따라 그 크기가 다르게 결정되므로 본 연구에서 소개하는 시험하중 산출방법을 모두 적용하여 결과를 비교해보고 최종적으로 적합한 방법을 선정하는 과정이 필요하다. Some methods of calculation of test load value from design load data were investigated which will be applied at strap installed full-scale airframe of composite aircraft. These methods were applied to left wing of KC-100 composite aircraft and the calculated test load values were compared with each others. Generally since test load values are differently calculated according to each aircraft type and position of straps, all calculation methods mentioned at this study need to be applied and compared to each aircraft. Finally the most appropriate method needs to be selected.
요철 형상의 스테인레스강 Z-핀으로 보강된 복합재 접합 구조물의 피로강도
최익현(Ik-Hyeon Choi),임철호(Cheol-Ho Lim) 한국항공우주학회 2013 韓國航空宇宙學會誌 Vol.41 No.12
저자는 최근 산업체 생산 현장에서 Z-피닝 복합재 구조물을 간편하게 제작할 수 있는 Z-피닝 패치 개념을 제안하였고, 이를 적용하여 복합재 단일-겹침 전단 접합시편을 제작하였으며, 정적시험을 통하여 54~68%의 접합강도의 향상을 발표하였다. 본 연구는 상기 연구의 후속으로서, 반복하중에 대한 접합강도의 향상을 측정하기 위하여 피로시험을 수행하였다. 사용된 Z-핀은 스테인레스강 핀이며, 복합재료와의 결합력을 증가시키기 위하여 표면을 요철 형상으로 가공하였으며, 화학적으로 부식시켰다. 반복하중 조건에서 접합강도는 약 98~125% 향상되었다. Recently the authors had proposed the z-pinning patch concept to simply manufacture z-pinned composite structures at industrial production site and manufactured composite single-lap shear joint specimens using the concept. Through static tensile test on the specimens they had obtained 54~68% improvement of the joint strength. As a sequential study of it, in this study, fatigue test has performed to measure an improvement of joint strength under cyclic loading. The z-pin’s material is stainless steel and its surface was specially machined into zagged shapes and chemically corroded to increase the connection force with composite materials. Approximately 98~125% improvement of the joint strength under cyclic loading was obtained.
새로운 z-피닝 기술로 제작된 복합적층판의 내충격 특성
최익현(Ik-Hyeon Choi),안석민(Seok-Min Ahn),염찬홍(Chan-Hong Yeom),황인희(In-Hee Hwang),이대성(Dae-Sung Lee) 한국항공우주학회 2009 韓國航空宇宙學會誌 Vol.37 No.7
본 논문에서는 복합적층판의 취약한 층간 특성을 보강할 수 있는 z-피닝 기술에 대하여 기존에 알려진 방법들을 소개하고, 최근 저자에 의하여 제안된 새로운 방법을 소개하였다. 새로운 방법을 적용하여 시제작된 z-피닝 시편들에 대하여 충격시험을 수행하고, 충격손상 영역을 측정하였다. z-피닝 기술이 적용되지 않은 일반 복합재 시편에 대해서도 동일한 시험을 수행하고, 두 결과를 서로 비교하였다. 결과적으로 새로운 z-피닝 기술은 기존의 기술에 비하여 양산에 적용하기가 매우 유리한 장점이 있으며, 새로운 z-피닝 기술이 적용된 복합적층판 시편들의 내충격 특성이 확실히 향상되고 있음을 알 수 있었다. In this paper, conventional z-pinning technology which can be used to reinforce inter-laminar property of laminated composites is introduced and new z-pinning technique recently proposed by author is also introduced. On some trial specimens manufactured by the new z-pinning technique, the low-velocity impact test was performed and impact damage area was measured. Similar impact test was performed on normal composite laminate specimens and those test results were compared to each other. Consequently, it can be seen that the new z-pinning technique is more useful in applying to mass production of z-pinned composite laminate structures than the conventional techniques and some clear improvement on impact resistance of z-pinned composite laminates manufactured by the new z-pinning technique is observed.
최익현 ( Ik Hyeon Choi ) 한국복합재료학회 2003 Composites research Vol.16 No.1
저속충격을 받는 복합적층판의 충격거동을 해석하기 위하여 많은 연구자들이 수정된 Hertz의 접촉법칙이나 실험적으로 구한 정적압입법칙을 사용하여 왔다. 본 연구에서는 이들이 사용했던 충격해석방법에 대한 물리적 의미를 고찰하였으며, 두 법칙의 차이가 실제로 적충판의 충격거동해석에 미치는 영향을 고찰하였다. 나아가 접촉법칙에 사용되는 접촉 상수 및 지수의 크기를 임의로 변경하여 해석함으로써 접촉법칙이 충격거동해석의 결과에 미치는 영향을 살펴보았다. 최종적으로 선형화된 접촉법칙을 적용하여도 충격거동해석을 정확히 수행할 수 있음을 보였다. 이 개념을 응용하면 충격문제해석을 위한 부가적인 프로그램 개발없이 범용 유한요소해석 프로그램으로도 복합적층판의 저속충격거동을 해석할 수 있음을 보였다. Usually many researchers have used the modified Hertzian contact law or experimental static indentation law to analyze impact response of composite laminates subjected to the low-velocity impact. In this study, physical meaning of the method using the laws was investigated and the difference between the analytical results obtained using the laws was also investigated. Furthermore parametric study on contact constant and exponent in the contact law was performed. Finally it was shown that a linearized contact law can be well applied to low-velocity impact response analysis of composite laminates. If this concept is used, commercial finite element software can be used to solve impact problem without making any auxiliary code.
Z-피닝 패치를 사용한 복합재 단일-겹침 전단 접합 시편의 정적강도
최익현(Ik-Hyeon Choi),임철호(Cheol-Ho Lim) 한국항공우주학회 2013 韓國航空宇宙學會誌 Vol.41 No.8
본 논문에서는 복합재 구조물의 제작 현장에서 쉽게 적용할 수 있는 장점을 갖는, 저자에 의하여 ‘Z-피닝 패치’로 명명된 새로운 Z-피닝 기술에 대하여 소개하였다. 시제작된 ‘Z-피닝 패치’를 사용하여 Z-핀이 박힌 복합재 단일-겹침 전단 접합시편을 성공적으로 제작하였고, 접합강도의 향상을 점검하기 위하여 시험을 수행하였다. Z-핀의 재질은 스테인레스강이며, 복합재료와의 접합력을 향상시키기 위하여 Z-핀의 표면은 요철 형상으로 가공하였으며, 화학적으로 부식시켰다. In this paper a new concept on z-pinning technology named by authors as ‘z-pinning patch’ will be introduced, which advantage is easy application at manufacturing site of composite structures. Using the trial manufactured z-pinning patch, the z-pinned composite single-lap shear joint specimens were successfully manufactured and tested to check the improvement of joint strengths. The z-pin’s material is stainless steel and its surface was machined as zagged shape and chemically corroded to improve joint force with composite materials.
( Ik Sung Choi ),( Kil Jong Yu ),( Dae Hyeon Cho ),( Ji Enu Oh ),( Chang Wook Jeong ),( Kwang Min Kim ),( Hyoun Soo Lee ),( Jung Won Lee ),( Dong Kyu Lee ),( Byung Soo Kwan ),( Sang Goon Shim ) 대한간학회 2018 춘·추계 학술대회 (KASL) Vol.2018 No.1
Aims: A direct-acting antiviral (DAA) drug is in the spotlight for the treatment of patients with chronic hepatitis C. The combination of sofosbuvir and ribavirin is more effective than the peg IFN and ribavirin in patients with genotype 2 HCV. The aim of this study was to evaluate the treatment efficacy and safety for GT2 HCV patients treated with sofosbuvir and ribavirin in a single center. Methods: The study was performed retrograde from May 2016 to December 2017 in GT2 HCV patients treated with sofosbuvir (400mg) plus ribavirin (800-1200mg; based on body weight) treatment. The primary endpoint was sustained virologic response at 12 weeks (SVR12). The secondary endpoint was the occurrence of side effects during treatment. Results: A total of 95 patients with GT2 HCV infection were enrolled, of which 92 were genotype 2a (96.8%) and 3 were 2b (3.2%). 2 patients were follow up loss, 1 patient discontinued treatment voluntarily. SVR12 was confirmed in 91 of 92 patients (98.91%). 1 patient with failed treatment were combined LC and HCC, HCV RNA was not detected at 4 weeks and 8 weeks after initiation of treatment, but HCV RNA detected at 12 weeks. Liver cirrhosis was diagnosed on the imaging studies or clinical manifestations and 24 patients were included (CTP-A; n=23, C; n=1). SVR12 with cirrhotic patients was 95.83%. The average HCR RNA titer was 2.46x10<sup>6</sup> IU/ml. Hemoglobin decrease (Mean ± SD; 2.95±1.19 g/dl) occurred in 21 patients during treatment and ribavirin dose reduction was required. Conclusions: This study was performed on a small group of patients compared with other studies, but showed that treatment with sofosbuvir and ribavirin was highly effective in patients with GT2 HCV infection. In aspect of safety, there was no serious side effects about treatment although hemoglobin decrease.