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충격하중을 받은 CFRP 적층판의 손상거동과 잔류굽힘피로강도
임광희,양인영,Im, Kwang-Hee,Yang, In-Young 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.6
In this paper, static and fatigue bending strengths of CFRP(carbon fiber reinforced plastic laminates having impact damage(FOD) are evaluated. Composite laminates used for this experiment are CF/EPOXY and CF/PEEK orthotropy laminated plates, which have two-interfaces[${0^0}_4{90^0}_4}$]$_sym$. A steel ball launched by the air gun colides against CFRP laminates to generate impact damages. The damage growth during bending fatigue test is observed by the scanning acoustic microscope(SAM). When the impacted side is compressed, the residual fatigue bending strength of CF/PEEK specimen P is greater that that of CF/EPOXY SPECIMEN B. On the other hand, when the impacted side is in tension, the residual fatigue bending strength of CF/PEEK speicemen P is smaller than that of CF/EPOXY specimen B. In the case of impacted-side compression, fracture is proposed from the transverse crack generated near impact point. On the other hand, fracture is developed toward the impact point from the edge of interface-b delamination in the case of impacted-side tension.
Evaluation and Application of T-Ray Nondestructive Characterization of FRP Composite Materials
Kwang-Hee Im(임광희),David K. Hsu 한국비파괴검사학회 2010 한국비파괴검사학회지 Vol.30 No.5
최근에는 T-ray(terahertz ray)를 이용한 비파괴기술이 새로운 분야로 주목을 받고 있다. 본 연구에서는 FRP 복합재료의 내재결함이나 레이업(lay-up) 특성을 검사 및 평가하기 위한 T-ray 시간영역 분광기(time-domain spectroscopy)를 활용하였으며 또한 이 T-ray 분광기의 일반적인 반사 및 투과모드를 이용하여 T-ray 이미지를 구현하였다. 특히, 2개의 톱날 인공결함이 내재한 GFRP 복합재의 평가방법을 제시하였다. CFRP 복합재료에 대해서는 T-ray 전파는 탄소섬유로 인해 진행 장해를 받는다. 이에 따라 T-ray의 전기장(E-field)의 방향과 탄소섬유 방향의 의존성을 분석하였다. 한편 인공결함인 알루미늄 테이프, 박리, 충격손상, 이물혼입 등을 T-ray를 이용하여 비파괴 검사 및 평가하였다. 이를 통해 FRP 복합재료의 T-ray비파괴평가의 적용 가능성 및 한계 등을 확인 할 수 있었다. Recently, (terahertz ray) applications have emerged as one of the most promising new powerful nondestructive evaluation (NDE) techniques. In this study, a new T-ray time-domain spectroscopy system was utilized for detecting and evaluating layup effect and flaw in FRP composite laminates. Extensive experimental measurements in reflection and thru-transmission modes were made to map out the T-ray images. Especially this was demonstrated in thick GFRP laminates containing double saw slots. In carbon composites the penetration of terahertz waves is limited to some degree and the detection of flaws is strongly affected by the angle between the electric field(E-field) vector of the terahertz waves and the intervening fiber directions. The artificial defects investigated by terahertz waves were bonded foreign material, simulated disbond and delamination and mechanical impact damage. The effectiveness and limitations of terahertz radiation for the NDE of composites are discussed.
임광희(Kwang-Hee Im),김지훈(Ji-Hoon Kim),David K. Hsu 한국생산제조학회 2012 한국생산제조학회지 Vol.21 No.2
A study of terahertz waves was made for the nondestructive evaluation of FRP (Fiber reinforced plastics) composite materials. The terahertz systems were consisted of time domain spectroscopy (TDS) and continuous wave (CW). The composite materials investigated include both non-conducting polymeric composites and conducting carbon fiber composites. Terahertz signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, a terahertz pulse was not able to detect a material with conductivity. The CFRP (Carbon fiber reinforced plastics) laminates were utilized for confirming the experimentation in the terahertz NDE. In carbon composites the penetration of terahertz waves is quite limited and the detection of flaws is strongly affected by the angle between the electric field direction of the terahertz waves and the intervening fiber directions. A refractive index (n) was defined as one of mechanical properties; so a method was obtained in order solve the “n” in the material with non-conductivity. The usefulness and limitations of terahertz radiation are investigated for the NDE of FRP composites.
One-Sided Nondestructive Evaluation of CFRP Composites By Using Ultrasonic Sound
Kwang-Hee Im(임광희),Gui-Lin Zhang(장계림),Sung-Rok Choi(최성록),Chang-Hee Ye(예창희),Je-Sung Ryu(류제성),Soo-Hwan Lim(임수환),Min-Gui Han(한민규),David K. Hsu 한국생산제조학회 2011 한국생산제조학회지 Vol.20 No.1
It is well known that stiffness of composites depends on layup sequence of CFRP(carbon fiber reinforced plastics) laminates because the layup of composite laminates influences their properties. Ultrasonic NDE of composite laminates is often based on the backwall echoes of the sample. A pair of such transducers was mounted in a holder in a nose-to-nose fashion to be used as a scanning probe on composites. Miniature potted angle beam transducers were used ( Rayleigh waves in steel) on solid laminates of composites. Experiments were performed to understand the behavior of the transducers and the nature of the waves generated in the composite (mode, wave speed, angle of refraction). C-scan images of flaws and impact damage were then produced by combining the pitch-catch probe with a portable manual scanner known as the Generic Scanner (”GenScan”). The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to fiber orientation of the CFRP composites, including low level porosity, ply waviness, and cracks. Therefore, it is found that the experimentally Rayleigh wave variation of pitch-catch ultrasonic signal was consistent with numerical results and one-side ultrasonic measurement might be very useful to detect the defects.
첨단 NDE 기법을 이용한 풍력터빈 블레이드의 페인팅 두께 모니터링 평가기법
임광희(Kwang-Hee Im),장계림(Gue-Lin Zhang),김우진(Woo-Jin Kim),정예원(Ye-Won Jeong),조철현(Chul-Hyun Cho),김선규(Sun-Kyu Kim),조영태(Young-Tae Cho),우용득(Yong-Deuck Woo) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The composite materials are being utilized on the various areas. Here, the paint used for wind blades was experimentally analyzed which data agreed with known data. Using these characterized material properties, the characteristics were successfully demonstrated through NDE behavior propagating through the painting materials to acquire the refractive index. Both ultrasonic and T-ray techniques were used to analyze the thickness of paint on the GFRP (Glass fiber reinforcement plastics) composites. The non-destructive evaluation (NDE) technique has been established for measuring the thickness. Good results have been obtained in tests on the thickness of the standard painted samples.
CFRP 적층재의 잔류피로 굽힘강도에 미치는 열습의 영향
임광희(Im Kwang Hee),박노식(Park No Sick),양인영(Yang In Young) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.11_1
This paper aims at the static and fatigue bending strengths of CFRP <carbon fiber reinforced plastic> laminates subjected to hygrothermals. The specimens which had different stacking composition, orthotropic and Quasi -isotropic laminated plates, were prepared for this experiment. A steel ball launched by the air gun collides against CFRP laminates to generate impact lamages, and the 3-point fatigue bending test is carried out by using the impacted laminates to investigate the influence of hygrothermals on the effect on the fatigue. strength of CFRP laminates.
임광희(Kwang-Hee Im),정종안(Jong-An Jeong),David K. Hsu,이길성(Kil-Sung Lee) 한국생산제조학회 2012 한국생산제조학회지 Vol.21 No.1
A study of terahertz waves (T-ray) was made for the nondestructive evaluation of FRP (Fiber reinforced plastics) composite materials. The to-be-used systems were time domain spectroscopy (TDS) and continuous wave (CW). The composite materials investigated include both turbine blades of wind energy (non-conducting polymeric composites) and conducting carbon fiber composites. Terahertz signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, a terahertz pulse was not able to detect a material with conductivity. This was demonstrated in CFRP (Carbon fiber reinforced plastics) laminates. Refractive index (n) was defined as one of mechanical properties; so a method was solved in order solve the “n” in the material with the cut parts of the turbine blades of wind energy. The defects and anomalies investigated by terahertz radiation were foreign material inclusions and simulated disband. Especially, it is found that the T-ray went through the turbine blade with greater thickness (about 90mm).