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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.
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.