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임광희(Kwanghee Im),김승기(Seungki Kim),김태훈(Taehun Kim),김한슬(Hanseul Kim),David K. Hsu,박제웅(Jewoong Park),양인영(Inyoung Yang) 한국자동차공학회 2008 한국자동차공학회 지부 학술대회 논문집 Vol.2008 No.11
It is very important to detect fiber orientation error in composite laminates because the layup of a CFRP composite laminates affects the properties of the laminate, including stiffness, strength and thermal behavior. An NDE technique for stacking orientation determination would be very beneficial because of layup orientation influence to the laminate stiffness. Usually, it is found that ultrasonic shear wave is pretty sensitive to fiber direction of CFRP composite laminates. An investigation of shear wave ultrasonic technique was carried out in order to detect stacking orientation error for quasi-isotropy composite laminates. Also, a jig is developed for generating a shear wave. A pyramid with an isosceles triangle with two 45° was made of aluminum to generate shear waves using two longitudinal transducers based on ultrasonic-polarized mechanism. Also, the signal splitter was connected to the pulser jack on the pulser/receiver and to the longitudinal transducers. An investigation of shear wave ultrasonic technique was carried out in order to generating shear wave.
On Ultrasonic Techniques of Fiber Orientation in CFRP Composite Laminates
임광희(Kwanghee Im),김영남(Youngnam Kim),나승우(Seoungwoo Na),이길성(Kilsung Lee),David K. Hsu,박제웅(Jewoung Park),심재기(Jaeki Sim),양인영(Inyoung Yang) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The layup of a CFRP (carbon-fiber reinforced plastics) composite laminates affects the properties of the laminate, including stiffness, strength and thermal behavior. It is very important to detect ply error before the laminate is cured for both manual procedure and fiber placement procedure. An ultrasonic technique would be very beneficial, which could be used to test the part after and before curing laminates and requires less time than the optical test. Also cross-polarized scan is very sensitive to the layup errors and ply misorientations. Scanners were set out for different measurement modalities for acquiring ultrasonic signals as a function of in-plane azimuthal angle. Firstly, a manual scanner was built for making transmission measurements using a pair of normal-incidence shear wave transducers to find the effect of fiber misorientations of composite laminates. Also a method for nondestructively determining the ply layup in a composite laminate is presented. The method employs a normal-incidence longitudinal ultrasound to perform C-scan of ply interfaces of the laminate. And a ply-by-ply vector decomposition model has been developed, simplified, and implemented for composite laminates fabricated from unidirectional plies. Test results between after and before curing laminates with model data were compared for a fiber orientation of the laminates.
고온·고습의 온도 변화에 따른 CFRP 모자형 단면부재 강도저하 평가
국현(Hyun Kook),임광희(Kwanghee Im),양인영(Inyoung Yang) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
CFRP Composites have light weight and high strength. CFRP Composite material feature superior heat and corrossion resistance, and these benefits enables the gradual applications on aerospace industries and sports-entertainment business. However, CFRP Composite materials have the weakness in hygrothermal environment and shock resistance. Especially, moisture absorption into composite material can change molecule arrangement and chemical properties under hygrothermal environment. This study is CFRP hat shaped sectional members compared and analyzed on the progress chang of moisture absorption ration after setting up temperature of 60 and 80 degrees C in order to comprehend how the change in the temperature influences on moisture absorption status inside CFRP composite materials.
초음파 이미지와 피크지연 속도측정법을 이용한 탄소탄소(C/C)복합재료 특성평가
허욱(Uk Heo),임광희(Kwanghee Im),양인영(Inyoung Yang) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Carbon/Carbon(C/C) composite materials have been used aircraft parts, automotive brake disk, etc. because of excellent heat-resisting property in super high temperature, excellent antiabrasion and excellent mechanical properties. It is desirable to perform ultrasonic testing to grasp Characteristic of this C/C composite materials and homogeneity of its parts. In this work, we applied ultrasonic image and a peak-delay measurement method to C/C composite which could cause inhomogeneity under manufacturing process. We had put inspection material into water tank to estimate homogeneity of materials using automated acquisition scanner and mapped a ultrasonic image to estimate the material property inhomogeneity. Also, low frequency(5㎒) pulse-echo technique based on both amplitude and time-of-flight of the ultrasonic pulse were used for estimating ultrasonic time-of-flight. Surface of the material was observed with using an electron microscope and those were compared with ultrasonic image. Therefore variation of ultrasonic velocity was correlated to those of material density, which is based on the peak-delay measurement method.
자동차 구조부재용 Al-CFRP 사각 혼성부재의 굽힘 특성
김정호(Jungho Kim),임광희(Kwanghee Im),편석범(Seokbeom Pyeon),양인영(Inyoung Yang),김지훈(Jihoon Kim) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The structural material which is used mainly in automobile or aircraft structure is going to change the aluminum alloy or composite material. On the study, it applied one of compound materials, CFRP. CFRP(Carbon fiber reinforced plastics) including light-weight, stiffness and hard condition widely used in various fields including space and aviation industries, sports and leisure industries and general structural members and parts. The material, however, has a serious drawback of brittle fracturing. It is difficult to use just CFRP material for structural members. So, it introduced the idea of hybrid composite material. It was manufacture by wrapping CFRP prepreg sheet outside aluminum square member that was using automobile structural members and having light-weight in autoclave. As the CFRP is an anisotropic material whose mechanical properties change with its stacking sequence or angle, special attention was given to the effects of the fiber orientation angle on the bending characteristics of Aluminum & CFRP hybrid square member. For comparing bending characteristics of Aluminum & CFRP hybrid square members with those of pure aluminum and CFRP member, tests were performed for hybrid member respectively.
경량화용 Al/CFRP 사각부재의 적층각에 따른 충격압궤특성
이길성(Kilsung Lee),차천석(Cheonseok Cha),정진오(Jinoh Chung),임광희(Kwanghee Im),심재기(Jaeki Sim),양인영(Inyoung Yang) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_2
In this study, the Al/CFRP structural members which are composed of square shaped aluminum members wrapped with CFRP (Carbon Fiber Reinforced Plastics) outside were manufactured to get a synergy effect when the Al/CFRP member is combined with the advantages of each members, such as energy absorption by the stable folding deformation of the aluminum member and by the high specific strength and stiffness of the CFRP member. The impact collapse tests were performed for the Al/CFRP members. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, are changed with its fiber orientation angle, special attention was given to the effects of the fiber orientation angle of CFRP on the collapse characteristics of the Al/CFRP members.
[안전부문] 박육부재의 에너지흡수 제어에 관한 실험적 연구
김선규(Sunkyu Kim),황창숙(Changsook Hwang),이현(Hyun Lee),임광희(Kwanghee Im),양인영(Inyoung Yang) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_2
Automobiles should be designed to meet the requirements and standards for the protections of passengers in a car accident. One of safety factors is an absorbing capacity in collision. Many vehicles have been designed based on the criterion of the absorbing capacity. Therefore a controller has been developed in order to control and increase the absorbing capacity of impact energy in automobile collision.<br/> Aluminum alloy(Al) tubes(circular and square) are tested by axial loading. The energy absorbing capacity of AI tubes have been estimated in cases of with-controller and without-controller, respectively based on height, thickness of an controller.<br/>
계면수 변화에 따른 Al/CFRP 혼성구조부재의 에너지 흡수 특성
서현경(HyeonKyeong Seo),황우채(Woochae Hwang),민한기(Hanki Min),임광희(kwanghee Im),양인영(Inyoung Yang) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The aluminum or CFRP is representative of light-weight materials. The aluminum tubes absorb energy by stable plastic deformation and the CFRP tubes absorbs energy by unstable brittle failure with higher specific strength and stiffness. Based on the respective collapse characteristics of aluminum and CFRP tubes, the aluminum CFRP compound tubes were manufactured to get a synergy effect when the aluminum CFRP tubes were combined with the advantages of each tube. This paper is to investigate the collapse characteristics of square or circular shaped aluminum CFRP compound tubes subjected to quasi-static axial collapse tests which were conducted by changing the stacking conditions. The aluminum CFRP compound tubes were made of8 layers of these sheets and they are stacked at different interlaminar numbers with outer orientation angle 90°, due to better collapse characteristics than that with 0 degrees. Test results showed that the collapse of the aluminum CFRP tubes complemented unstable brittle failure of the CFRP tube due to the ductile characteristics of the inner aluminum tube. It turned out that interlaminar numbers of aluminum CFRP compound tubes have no influence on the energy absorption and collapse modes of the tubes.