Papers by Author: In Young Yang

Abstract: CFRP (Carbon Fiber Reinforced Plastics) is an anisotropic material which is the most widely adapted lightweight structural member. CFRP of the advanced composite materials as structure materials for vehicles has a widely application in lightweight structural materials of air planes, ships and automobiles because of high strength and stiffness. The CFRP Square members were made of 8ply unidirectional prepreg sheets stacked at different angles and interface numbers. Based on the collapse characteristics of CFRP member, the collapse characteristics and energy absorption capability were analyzed. The impact collapse tests were carried out for each section member. The purpose is to examine experimentally absorption behavior and strength evaluation depending on changes in the stacking configuration when the CFRP Square member s with different stacking configuration is exposed to separate impact velocity.

Abstract: There has been greater demand on fuel mileage improvement and reduced CO₂ emission in automobile without sacrificing safety. To meet these requirements, light weight car body is widely adopted. In addition, advanced country already started the strict regulation on fuel mileage and exhaust gas emission because of energy depletion by automobile and severe environmental contamination. Especially, during the initial stage of car design, side member of front side that absorbs significant amount of energy should be precisely evaluated for collapsing and energy absorption prior to estimate safety performance on frontal collision of car. Therefore, CFRP double hat and hat-shaped member were prepared to supplement the issues of splitting between “ᄃ” shaped member and planar one. According to stacking configuration, energy absorption characteristics via impact collapsing experiment were evaluated to acquire CFRP double-hat shaped member.

Abstract: CFRP composite material, which is reinforced with carbon fiber, features superior heat and corrosion resistance, and these benefits enables the gradual applications on aerospace industries and sports-entertainment business. However, guarantee on superior strength and rigidity on harsh condition, such as hot moisture environment and collision load is extremely difficult. Therefore, in study moisture absorption test was conducted until complete moisture absorption in test specimen using hygrothermal heat chamber to evaluate strength degradation in CFRP composite under hygrothermal environment. As a result, the effect of moisture absorption and impact loads of approximately 50% reduction in strength are shown.

Abstract: CFRP composite with light weight, high strength, and high elasticity compared to metal is widely used rather than previous steel plates. However, CFRP composite material has the weakness in hygrothermal and impact collapsed environment. Especially, moisture absorption into composite material under hygrothermal environment can change molecule arrangement and chemical properties. Therefore, the purpose of this study lies in acquiring quantitative design data that can be put into the practice by comparing and evaluating the strength degradation under the environment where the moisture is absorbed by conducting static and impact collapse test after setting extreme condition for CFRP composite that takes consistent form such as frontal side members that is actually used in vehicle. This study compared and studied change in the progress of a moisture absorption ratio after setting up the temperature of 60 degrees, and 80 degrees in order to comprehend how the change in the temperature impacts on moisture absorption status inside CFRP composite materials. As a result of this study showed that the strength reduction of about 50% appears due to moisture absorptions. In addition, it showed that the higher the temperature is, the more rapid the progress of a moisture absorption inside CFRP composite materials is. Accordingly, it showed that the change in matrix also has a weak point.

Abstract: Transport is the safety and comfortableness during the transportation of passenger to desired location. Therefore, goals in transport design can be summarized as environment-friendliness and safety. Demand for weight reduction of transport has been growing in order to solve the environmental problems. In many countries, environment conservation forces the enhanced regulation on gas mileage and emission gas due to exhaustion of energy resource, adding an extra weight of environment pollution. CFRP(Carbon Fiber Reinforced Plastic) which the advanced composite materials has a widely used in lightweight structural materials of aircraft, ship and vehicle because of high strength and stiffness. In this study, collapse mode and energy absorption capability double CFRP hat-shaped section members were analyzed. The stacking condition were selected to investigate the effect of the fiber orientation angle (±15°, ±45°, 90°, 90°/0°and 0°/90° where 0°direction coincides with axis of the member)on the energy absorption of the CFRP double hat-shaped section members. The collapse mode and energy absorption capability of CFRP double hat-shaped section members was analyzed according to the change of the fiber stacking condition of CFRP.

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.

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.

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.

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.

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.