복합재료 직교적층판의 비파괴 평가에 관한 연구

나승우,양인영 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.2

A new ultrasonic test method is proposed to obtain elastic constants of unidirectional composite materials nondestructively. This work exhibits how susceptive the shear ultrasonic waves are to a little misoriented plies according to the angle variation of shear ultrasonic waves 0°, 45° and 90°. Also, it is shown that shear waves, particularly the transmission mode with the transmitter and receiver perpendicular to each other, have high sensitivity for detecting anomalies in fiber orientation and ply layup sequence that may occur in the manufacturing of composite laminates. Experimental results are agreed with modeling solutions which were based on decomposition of shear wave polarization vector as it propagates through the composite laminates. This wave appeared considerably to be sensitive to CFRP composites to the thickness direction along in-plane fibers.

의사등방성 CFRP 적층판의 충격손상과 잔류강도에 미치는 고온환경의 영향

나승우,양인영 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1

본 연구에서는 고온하에서 의사등방성 CF/EPOXY 적층판이 이물충격손상을 받을때 충격에너지의 크기와 잔류굽힘강도와의 관계 및 충격에너지의 크기와 잔류강성계수와의 저하관계를 고찰하여 온도의 변화가 CFRP 적층재의 충격손상에 어떤 영향을 미치는가를 실험적 관계에서 고찰하였다. 상온에서는 충격손상에 의한 잔류강도 저하현상은 거의 없으나 시험편의 표면온도가 상승함에 따라 잔류강도는 저하하였다. 고온하에서 충격손상에 의한 굽힘강도 잔류계수 역시 충격면이 인장을 받은 경우가 충격면이 압축을 받는 경우 보다 작았으며, 굽힘강성 잔류계수는 온도변화 및 충격손상에는 상관없이 거의 일정하였다. This study deals with the effects of impact damages of CFRP laminates with respect to temperature changes through an observation of the interrelations between the impact energy vs. residual rigid modulus when the quasi-isotropic CFRP laminates are subjected to FOD (Foreign Object Damage) In the room temperature, the decreasing of the residual strength didn't generate by the impact damages. Also, with raising the specimen temperatures, the residual strength decreased for both the unimpacted specimen and the specimen subjected to impact damages. In the specimen of quasi-isotropic CF/FPOXY(〔0° 2/90°2/45° 2/-45°2〕sym), the decreasing for impact damage and the temperature change didn't occur in the case of the tension side of the impact surface than in compression side, In the case of impact surface under the tension, it was found that a buckling of local delamination was generated at the time the delamination section (F interfaces) was subjected to the compression. The CF/EPOXY specimen of quasi-isotropic laminates shows that the retention factors of bending strength is lower in the tension side of the impact surface than in the compression side. Bending stiffness retention factor remains almost constant irelevant to the temperature changes and the magnitude of impact damages.

초음파 탐촉자의 분극성에 따른 CFRP 복합적층판 평가에 관한 연구

나승우,임광희,양인영 한국산업안전학회 2002 한국안전학회지 Vol.17 No.1

This paper shows error in the polarization direction on ultrasonic transducers how sensitive the shear ultrasonic waves are to a little misoriented plies according to the angle variation of shear ultrasonic waves 0˚, 45˚ and 90˚. Also, it is shown that shear waves, particularly the transmission mode with the transmitter and receiver perpendicular to each other, have high sensitivity for detecting anomalies in fiber orientation and ply layup sequence that may occur in the manufacturing of composite laminates. Experimental results are agreed with a modeling solutions which was based on decomposition of shear wave polarization vector as it propagates through the composite laminates. This wave appeared considerably to be sensitive to CFRP composites to the thickness direction along in-plane fibers.

고온에서 충격을 받는 CF/PEEK 적층재의 충격손상과 잔류강도에 과한 연구

나승우,송상기,김기형 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.2

선진 재료인 탄소섬유강화 복합재(Carbon Fiber Reinforced ; 이하 CFRP라한다)는 비강성(탄성률/밀도), 비강도(인장강도/밀도)가 크기 때문에 구조경량화가 강하게 요구되는 우주항공분야의 구조재료로서 널리 이용되고있다. 그러나 우주힝공 분야에 널리 사용되고있는 CF/EPOXY적층재의 주요 제약은 고열 고습(hot wet) 성능에 문제가 있기 때문에 가혹한 환경하에서 성능을 유지시키기 위해 고성능 우주구조재로 CF/PEEK 적층재가 개발되었다. 대형 판넬에 작은 물체(공구 등)가 충돌할 경우는 충격손상은 소규모여서 설계시에는 충돌후의 압축잔류강도(CAI)가 문제가 되지만 제트엔진 앞부분에 CFRP적층재를 이용할 경우 비교적 소형의 부품(靜翼등)에 새, 작은돌 등을 흡입할 때에 발생하는 이물충격손상(FOD : Foreign Object Damage)을 피할 수사 없으며 손상은 부품전체에 영향을 미쳐 수명저하를 가져온다. 따라서 부품설계시에 CFRP적층재의 충격손상의 주 파괴모드인 모재크랙 + 층간박리 연성파괴를 고려한 내충격특성 ,평가수법이 필요하게된다. 특히, CF/PEEK 적층재가 점차 우주항공부재로서 사용이 확대됨에 따라 우주환경 (-140 ∼ 120℃) 및 비행중의 온도환경(-73 ∼ 80℃)에 노출되기 때문에 가혹한 온도환경에서의 FOD 손상이 문제가 되며 잔류수명 평가문제는 극히 중요한 문제이다. 따라서, 본 연구에서는 "고성능 우주구조재로 개발된 CF/PEEK 적층재가 고온분위기하에서 이물충격손상을 받을 때 생기는 층간박리, 모재크랙등이 온도변화에 따라 어떻게 변화하며 잔류수명에 어떠한 영향을 미치는가를 실험적인 관점에서 고찰하는 것을 목적으로 한다. An experimental study on the effects of temperature change on the impact damages of CF/PEEK laminates was carried out, an observation of the interrelations between the impact energy vs. delamination area and transverse crack, the impact energy vs. residual bending strength, and the interlayer delamination area vs. the decreasing of the residual flexural strength for CF/PEEK composite laminates subjected to FOD(Foreign Object Damage) under high temperatures. Following important facts were obtained from the study; (1) Higher surface temperature of the CF/PEEK laminates, gives less tendency toward the generation of delamination due to a higher initial damage energy that initiates delamination by the impact damages. (2) Delamination Area per Unit Impact Energy in the impact damages decreases linearly with the temperature increase; ie., the delamination development rate becomes lower with raising the specimen temperature (3) It has been found that the residual bending strength is always lower in the tension side of the impact surface than in compression side because of local delamination buckling.

초음파 트랜스듀셔의 극성현상 평가에 관한 연구

나승우,양이영 朝鮮大學校 機械技術硏究所 2001 機械技術硏究 Vol.4 No.1

This paper shows shear wave behavior of CFRP composite laminates as a polar grid form to evaluate vibration pattern of ultrasonic transducers, which gives measured modelling fundamental contents of nondestructive evaluation. Polarized direction can be obtained by using a c-scanner and sensitivity of transducers is founded when using through-transmission method of two transducers. And modelling of vector decomposition is presented based on ply-to-ply method to apply practicable nondestractive evaluation of CFRP laminate lay up. This modelling decomposes the transmisson of a linearly polarized wave into orthogonal components through each ply of a laminate. It is found that a high provable shows between the model and experimental developed in characterizing layup of CFRP composite laminates

직교이방성 CFRP적층판의 초음파 탐사에 관한 연구

임광희,양인영,나승우 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.2

This work ethibits how susceptive the shear ultrasonic waves are to a little misoriented plies according to the angle variation of shear ultrasoic waves 0˚, 45˚ and 90˚. Also, it is shown that shear waves, particularly the transmission mode with the transmitter and receiver perpendicular to each other, have high sensitivity for detecting anomalies in fiber orientation and ply layup sequence that may occur in the manufacturing of composite laminates. Experimental results are agreed with modeling solutions which were based on decomposition of shear wave polarization vector as it propagates through the composite laminates. This wave appeared considerably to be sensitive to CFRP composites to the thickness direction along in-plane fibers .

<i>Vigna angularis</i> inhibits IL-6-induced cellular signalling and ameliorates collagen-induced arthritis

Oh, Hyun-Mee,Lee, Seung Woong,Yun, Bo Ra,Hwang, Byung Soon,Kim, So Nam,Park, Chan Sun,Jeoung, See-Hwa,Kim, Hyun-Kyu,Lee, Woo Song,Rho, Mun-Chual Oxford University Press 2014 Rheumatology Vol.53 No.1

<P><B>Objectives.</B> The present study was conducted in order to assess whether extracts or isolated compounds from <I>Vigna angularis</I> were able to suppress IL-6 signalling and to show the therapeutic effect on collagen-induced arthritis (CIA) in mice.</P><P><B>Methods.</B> The effect of <I>V. angularis</I> on IL-6 signalling was studied by measuring Stat3-dependent luciferase activity, expression of inflammation-related genes, and phosphorylation of Janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3) and extracellular signal-regulated kinase (ERK) induced by IL-6. CIA was induced by immunizing with bovine type II collagen. <I>V. angularis</I> extract (VAE) was administrated orally at 50 and 100 mg/kg from day 1 to day 28. Induction of arthritis was evaluated with a visual scoring system and histological analysis.</P><P><B>Results.</B> Extracts or two triterpenoid compounds from <I>V. angularis</I> showed potent inhibitory effects on pSTAT3-inducible luciferase activity, STAT3 tyrosine phosphorylation and the expression of inflammation-related genes induced by IL-6. Administration of VAE significantly suppressed the progression of CIA, accompanied by a reduced antibody response to type II collagen and protection from tissue damage in knee joints.</P><P><B>Conclusion.</B> Administration of VAE has a therapeutic effect on CIA and this effect is associated with the inhibitory activity on IL-6/STAT3 signalling. These results suggest that extracts or compounds from <I>V. angularis</I> could be a useful treatment for diseases related to IL-6, including RA.</P>

CFRP 복합적층판의 적층배향·계면수에 따른 저속충격특성

임광희,박노식,나승우,김영남,이현,심재기,양인영 한국공작기계학회 2001 한국생산제조학회지 Vol.10 No.6

In this paper, this study aims at the evaluation on the characteristics of CFRP laminate plates using a falling weight impact tester. The experiment was conducted on several laminates of different orientation. A system was built for measuring the impact strength of CFRP laminates in consideration of stress wave propagation theory using a falling weight impact tester. Delamination areas of impacted specimens for the different ply orientation were measured with ultrasonic C-scanner to find correlation between impact energy and delamination area. Absorbed energy of quasi-isotropic specimen having four interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the greater the energy absorbed. The absorbed energy of a hybrid specimen containing a GFRP layer was higher than that of normal specimens.

工業系 敎師의 再敎育을 위한 硏修 프로그램의 開發에 관한 硏究

李來然,劉承坤,羅聲雄,禹鎬吉 충남대학교 공업교육연구소 1983 論文集 Vol.6 No.2(A)

This study is intended to provide a more effective curriculum for the In- Service Training Program of industrial technical teachers. The curricula which have been used during last five years were carefully analyzed and the main conclusions are suggested as follows; 1) It must be given to the teachers to take optional subjects. 2) Experiments should be reinforced make up for the understanding of theory. 3) Practical studies and factory investigations have to be provided to the teachers during the In-Service Training Program. In case of needs, the expert engineer of industries become a instructor to the teachers for explaining the up-to-date industrial techniques and theories. 4) The teachers who attending the In- Service Training Program should take an active interest in the program for getting a remarkable results.

온도변화가 CF/PEEK 적층재의 충격 후 굽힘강도에 미치는 영향

양인영,정종안,나승우 한국안전학회 2003 한국안전학회지 Vol.18 No.2

In this paper, when CF/PEEK laminates for high efficiency space structure are subjected to FOD(Foreign Object Damage), the effects of temperature change on the impact damages(interlaminar separation and transverse crack) of CF/PEEK laminates and the relationship between residual life and impact damages are experimentally investigated. Composite laminates used in this experiment are CF/PEEK orthotropic laminated plates. which have two-interfaces [0˚₄/ 90˚_(8)/0˚₄]o A steel ball launched by the air gun collides against CF/PEEK laminates to generate impact damages. And then CF/PEEK specimens with impact damages are observed by a scanning acoustic microscope under room and high temperatures. In this experimental results, various relations are experimentally observed including the delamination area vs. temperature change, the bending strength vs. impact energy and the residual bending strength vs. impact damage of CF/PEEK laminates.