• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.33-38
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• 2001

This study aims to systematically research the various phenomena which arise from compression molding of fiber reinforced plastic composites. Long fiber reinforced plastic composites are rib type compression molded in order to measure the orientation in products, and the specimens are photographed with soft X-ray. The intensity of the photograph is applied by an image scanner, and the fiber orientation distribution of products is measured by using an image processing technique.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.184-187
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• 2002

Compression molding was specifically developed for replacement of metal components with composites. As the mechanical properties of the products are dependent on the separation and orientation, it is important to research the fiber mat structure and molding conditions. In this study, the effects of the fiber mat structure(NP: 5, 10, 25punches/$\textrm{cm}^2$) and the mold closure speed($\dot{\textrm{h}}$=0.1, 1, 10mm/min) on the viscosity of composites were discussed. The composites is treated as a Non-Newtonian power-law fluid. The parallel-plate plastometer is used and the viscosity is obtained from the relationship between the compression load and the thickness of the specimen.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.313-318
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• 2001

Compression molding is widely used process for the industrial forming of fiber reinforced plastic articles. Its applications are of an extreme variety and the products range from large parts, such as used in the automotive industry to much smaller objects. In this paper, distribution of fiber orientation by the image processing method for rib type compression molded products of each fiber content is measured. And the effects of fiber content, product size on the orientation state are discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.2
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• pp.296-302
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• 2010

If the fiber reinforced plastic is exposed to the moisture for a long period of time, most of moisture absorption occurs on the resin place, thus dropping cohesiveness between the molecules as the water molecules permeated between high molecular chains grant high molecular mobility and flexibility. Also as the micro crack occurs due to the permeation of moisture on the interface of glass fiber and epoxy resin, it is developed to the overall damage of interface place. Hence, the study on absorption is essential as the mechanical and physical properties of fiber reinforced composites are reduced. However, the study on absorption has the inconvenience needing to expose composite materials to fresh water or seawater for 1 month or up to 1 year. Therefore, this study has exposed fiber reinforced composites to fresh water and has developed a model with an accuracy of 98% after comparing the analysis value obtained by using ANSYS while basing on the experimental value of property decline by absorption and the basic properties of glass fiber and epoxy resin used in the experiment.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.25-30
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• 2017

Carbon-fiber-reinforced plastic (CFRP) composite materials have been widely used in various industrial fields because the design variables can be adjusted according to the application of the required structure. Thermosetting and thermoplastic resins are used as the base materials of CFRP composites for the lightweight construction of automotive components. Thermoplastics have several advantages such as no curing and recyclability compared to thermosetting resin. In this study, CFRP composites were made using the Long-Fiber Thermoplastic-Direct (LFT-D) process. The LFT-D process includes an in-line production system that directly impregnates a thermoplastic resin, extrudes the composite material, and molds it. This process increases the strength and decreases the molding time. The tensile strength characteristics on the mechanical properties of CFRP were analyzed according to the parameters of LFT-D based on thermoplastics. To analyze the properties of CFRP, the specimens were prepared based on the tensile test standard ASTM 3039 of composite materials.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.136-142
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• 1999

The injection molded part shrinks in the process of solidification by the amount of the coefficient of linear thermal expansion multiplied by the temperature difference between the coefficient of linear thermal expansion multiplied by the temperature difference between the room temperature and the temperature at which the solid structure is formed in the mold And it is called warpage for this type of deformation that shrinkage are not uniform throughout the injection molded part. To predict warpage phenomena in the articles the results obtained theoretically from the change of mold temperature fiber content of composites have been compared with exsperimental results.

• Journal of Korea Ship Safrty Technology Authority
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• no.7 s.25
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• pp.64-76
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• 2008

This paper describes the failure mechanism and Charpy impact test of Fiber glass Reinforced Plastic composites which it was actually used for side plate of vessel. There are two examinations. The examination I, the specimens which it given temperature range $-25^{\circ}C$-$50^{\circ}C$ and with different initial notch length did impact test and then it compared impact energy(Uc) and impact fracture toughness(GIC). The examination II, the specimens which it putted into fresh water and sea water for scheduled hours did impact test and it compared impact energy(Uc) and impact fracture toughness(GIC). From examination I, it showed that impact energy(Uc) and impact fracture toughness(GIC) were peak at ambient temperature and decrease as temperature reduced. Fracture toughness(GIC) showed increase as initial notch length reduced. From examination II, impact energy(Uc) and impact fracture toughness(GIC) tended to increase which specimens putted in fresh water compared with sea water and maximum tolerance rate tend to decrease as permeation hours will be long.

• Journal of the Korea Convergence Society
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• v.10 no.5
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• pp.165-171
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• 2019

Engineering and Technology have been influencing a lot in the field of sports. Competitiveness, attributes of sports, have forced not only sports players but sports goods to enhance those performance. Particularly in the field of motorsports, the convergence of sports and technology has long been done to satisfy between performance and safety. In this study, strength analysis was carried with FEM to develop CFRP Laminate(Carbon Fiber Reinforced Plastic Laminate) bucket seat targeted to motorsports and car tuning industries and FIA($F\acute{e}d\acute{e}ration$ Internationale de l'Automobile) regulation was applied to design the racing seat and evaluate its strength. FEM modeling considered the attributes of composites was followed by strength evaluation based on Tsai-Wu failure index were done according to Lay-up sequence and layer numbers. The result showed that the lay-up sequence with stacking angle such as $[0^{\circ}/30^{\circ}/60^{\circ}/90^{\circ}/-30^{\circ}/-60^{\circ}]_4$ with 3mm form core was optimal selection in the field of weight and strength evaluation.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.2
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• pp.155-164
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• 2014

Carbon-fiber-reinforced plastic (CFRP) composites are increasingly being used in a variety of industry applications, such as aircraft, automobiles, and ships because of their high specific stiffness and high specific strength. Aircraft are exposed to high temperatures and high humidity for a long duration during flights. CFRP materials of the aircraft can absorb water, which could decrease the adhesion strength of these materials and cause their volumes to change with variation in internal stress. Therefore, it is necessary to estimate the characteristics of CFRP composites under actual conditions from the viewpoint of aircraft safety. In this study air-coupled ultrasonic testing (ACUT) was applied to the evaluation of water absorption properties of CFRP composites. CFRP specimens were fabricated and immersed in distilled water at $75^{\circ}C$ for 30, 60, and 120 days, after which their ultrasonic images were obtained by ACUT. The water absorption properties were determined by quantitatively analyzing the changes in ultrasonic signals. Further, shear strength was applied to the specimens to verify the changes in their mechanical properties for water absorption.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.889-895
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• 2012

Carbon fiber reinforced plastic (CFRP) composites have high specific stiffness and high specific strength. Therefore, they are increasingly being use, instead of conventional metallic materials in the aviation and automobile industries, where there is a strong demand for lightweight materials. In aircraft, the fuselage is exposed to severe conditions of high temperatures and high humidity. Therefore, it is necessary to estimate the strength of CFRP composites under real conditions from the viewpoint of aircraft safety. In this study, CFRP specimens were immersed in distilled water at $75^{\circ}C$ for a long time. Then, tensile tests were performed on these specimens, and the fracture characteristics of the fractured surfaces were analyzed using SEM. A fatigue test was performed on specimens immersed for 300 days with R=0.1, and it was confirmed that the fatigue life deteriorated in immersed specimens compared to specimens that were not immersed.