Papers by Author: In Young Yang

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Authors: Kwang Hee Im, Je Woong Park, David K. Hsu, Sun Kyu Kim, Young Tae Cho, Yong Jun Yang, In Young Yang
Abstract: A nondestructive technique would be very useful for evaluating the CF/Epoxy composite laminates. It is found that a pitch-catch signal was more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composites (damages, fiber orientation, low level porosity, ply waviness, and cracks). The depth of the sampling volume where the pitch-catch signal came from was relatively shallow with the head-to-head miniature Rayleigh probes, but the depth can be increased by increasing the separation distance of the transmitting and receiving probes. Also, a method was utilized to determine the porosity content of a composite lay-up by processing micrograph images of the laminate. The porosity content of a composite structure is critical to the overall strength and performance of the structure. The image processing method developed utilizes a free software package to process micrograph images of the test sample. The results from the image processing method are compared with existing data. Beam profile was characterized in unidirectional CFRP (Carbon fiber reinforced plastics) with using pitch-catch Rayleigh probes and the one-sided and two-side pitch-catch technique was utilized to produce C-scan images with the aid of the automatic scanner. Also, it is confirmed that the pitch-catch ultrasonic signal was corresponding with simulated results assuming in unidirectional CFRP composites.
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Authors: Ju Ho Choi, In Young Yang, Woo Chae Hwang
Abstract: Vehicle structure must be lightweight in order to improve fuel-efficiency and reducing exhaust fumes. The most important goals in designing automobile are safety and environment-friendliness. There are lots of studies on the crushing absorption energy of a structural members in automobile. The crashworthy behavior of circular composite material tubes subjected to axial compression under same conditions is reported in this paper. Energy absorption of CFRP circular member is affected by lamination conditions. Test was executed in order to compare the results to the energy absorption and collapse shape.
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Authors: Kil Sung Lee, Hyeon Kyeong Seo, Woo Chae Hwang, Jung Ho Kim, Yong Jun Yang, In Young Yang
Abstract: Currently, the most important objective in designing automobiles is to focus on environment-friendly and safety performance aspects. For the environment-friendly aspect, the issues relate to the shift towards lightweight automobile production, for improving fuel-efficiency and reducing exhaust fumes. However, in contrast, the issues of the safety performance such as crash safety, comfort level and muti-functional programs demand increase of automobile’s weight. Therefore, the design of automobile should be inclined towards the safety aspects, but at the same time, it also should consider reducing the structural weight of an automobile. In this study, for lightweight design of side member, CFRP side member was manufactured from CFRP unidirectional prepreg sheet. The stacking condition related to the energy absorption of composite materials, is being considered as an issue for the structural efficiency. Therefore, the axial collapse tests were performed with change of the stacking condition, such as fiber orientation angle and interlaminar number. The collapse modes and energy absorption characteristics were analyzed according to fiber orientation angle and interlaminar number.
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Authors: Kil Sung Lee, Kwang Hee Im, In Young Yang
Abstract: The purpose of this study was to develop lightweight hat shaped section side members which absorb the most of the energy during the front-end collision of vehicle. The hybrid side member was manufactured by combination of aluminum and CFRP. An aluminum or CFRP (Carbon Fiber Reinforced Plastics) member is representative lightweight materials but its axial collapse mechanism is different from each other. The aluminum member absorbs energy by stable plastic deformation, while the CFRP member absorbs energy by unstable brittle failure with higher specific strength and stiffness than those in the aluminum member. Based on the respective collapse characteristics of CFRP side and aluminum members, the hybrid side members were tested on the axial collapse loads to get a synergy effect when the 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. Energy absorption capability and collapse mode of the hybrid side members were analyzed.
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Authors: In Young Yang, Yong Jun Yang, Jun Woo Park, Kil Sung Lee, Young Tae Cho, Je Woong Park, David K. Hsu, Kwang Hee Im
Abstract: Carbon/carbon(C/C) composite materials have obvious advantages over conventional materials, which consist of carbon fibers embedded in a carbon matrix. It’s low density, high thermal conductivity and excellent mechanical properties at elevated temperatures make it an ideal material for aerospace applications especially aircraft brake disks. Because of permeation of coupling medium such as water, it is desirable to perform contact-less nondestructive evaluation to assess material properties and part homogeneity. In this work, a C/C composite material was characterized with non-contact and contact ultrasonic methods using automated acquisition scanner. . Due to the acoustic impedance mismatch found between most materials and air, a major limitation for air-coupled transducers, through-transmission mode was performed. Especially ultrasonic images and velocities for C/C composite disk brake were measured and found to be consistent to some degree with the non-contact and contact ultrasonic measurement methods. 400 kHz frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the inhomogeneity in material property. Non-contact measured results were compared with those obtained by the motorized system using contact drycoupling ultrasonics and through transmission method in immersion. Results using a proposed peak-delay measurement non-contact method corresponded well to the ultrasonic velocities of the contact pulse overlap method.
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Authors: Cheon Seok Cha, Kil Sung Lee, Seung Hoon Kim, Jin Oh Chung, In Young Yang
Abstract: Aluminum or CFRP (Carbon Fiber Reinforced Plastics) tube subjected to axial loading sustains load, and absorbs energy during axial collapse. The aluminum tube absorbs energy by stable plastic deformation, while the CFRP tube with higher specific strength and stiffness than those of the aluminum tube absorbs energy by unstable brittle failure. To achieve a synergy effect by combining the two members, aluminum/CFRP compound tubes were manufactured, which are composed of aluminum tubes wrapped with CFRP outside aluminum tubes with different fiber orientation angle of CFRP and number of plies. The axial quasi-static collapse tests were performed for the tubes. The collapse characteristics of the tubes were compared with those of respective aluminum tube and CFRP circular tube. 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. The collapse modes and the absorbed energy were influenced by the fiber orientation angle of CFRP and the number of plies. The absorbed energy per unit mass, which is in the light-weigh aspect, was higher in the aluminum/CFRP compound tube than in the aluminum tube or the CFRP tube alone.
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Authors: Ji Hoon Kim, Kil Sung Lee, In Young Yang
Abstract: The strength members, such as front-end side members, are subjected to axial compressive and bending load during collision. Therefore, it is important to consider energy absorption by the axial compression and the bending for design of effective strength members. And at the same time, it also should consider reducing weight of the members. In this study, CFRP (Carbon Fiber Reinforced Plastics) side members with single-hat-section shape were manufactured. The axial compression and the bending tests were performed for the members using universal testing machine, and the axial compression and the bending characteristics were analyzed. Stacking condition related to the energy absorption of composite materials is being considered as an issue for the structural efficiency. So the energy absorption of the member under the axial compressive load and the bending load were experimentally investigated.
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Authors: In Young Yang, Kil Sung Lee, Young Nam Kim, Jin Oh Chung, Cheon Seok Cha
Abstract: An aluminum or CFRP (Carbon Fiber Reinforced Plastics) tube is representative light-weight materials but its axial collapse mechamism is different from each other. The aluminum tube absorbs energy by stable plastic deformation, while the CFRP tube absorbs energy by unstable brittle failure with higher specific strength and stiffness than those in the aluminum tube. In an attempt to achieve a synergy effect by combining the two members, aluminum/CFRP square tubes were manufactured, which are composed of aluminum tubes wrapped with CFRP outside aluminum square tubes with different fiber orientation angle and thickness of CFRP, and axial collapse tests were performed for the tubes. The crushing behavior and energy absorption capability of the tubes were analyzed and compared with those of the respective aluminum square tubes and CFRP square tubes. Test results showed that the collapse of the aluminum/CFRP square tube complemented unstable brittle failure of the CFRP square tube due to ductile characteristics of the inner aluminum square tube. The collapse modes were categorized into four modes under the influence of the fiber orientation angle and thickness of CFRP. The absorbed energy per unit mass, which is in the light-weight aspect, was higher in the aluminum/CFRP square tube than that in the aluminum square tube or the CFRP square tube alone.
297
Authors: Ji Hoon Kim, Joo Yeung Jeong, Jung Min Bang, Jung Ho Kim, In Young Yang
Abstract: Carbon fiber reinforced plastics (CFRP) have high strength in comparison with dimensional stability, invariability of material property, high strength and rigidity, corrosion resistance. Therefore, CFRP is widely used in various fields including space and aviation industries, sports and leisure industries, and general structural members and parts. To achieve structural members of CFRP with high strength and rigidity, theoretical approaches is limited to isotropic material, and empirical studies have been conducted. As with other composite materials, CFRP shows different rigidity and strength due to difference in properties in fiber and matrix material. In this study, CFRP specimen with changing stack orientation angle was manufactured as general structural application, and bending strength and rigidity of the corresponding composite was measured. In addition, square aluminium tube reinforcement is applied to prevent the shortcoming of CFRP. Vacuum compressed CFRP via autoclave with square aluminium tube reinforcement material (Hybrid) was evaluated by changing of orientation angle.
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Authors: Joong-Suk Kook, In Young Yang, Tadaharu Adachi
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