• Composites Research
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• 제29권5호
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• pp.315-320
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• 2016

Conventionally, composite aircraft structures are fabricated within autoclave at high pressure. However, autoclave process has several disadvantages including high curing costs and limitation of part size. Recently, out-of-autoclave (OoA) processes have been investigated in many studies to replace conventional autoclave process. A newly developed OoA prepreg, using conventional ovens, can significantly reduce the curing costs and produce autoclave-quality parts. Nevertheless, manufacture of void-free complex shape structure using OoA process presents significant challenges because of the low consolidation pressure. In this study, integrated skin-spar-rib composite part was fabricated using OoA prepreg. And cross-sectional macro- and micro-graphs of the part were examined in order to assess the possibility of replacing conventional autoclave process.

• Composites Research
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• 제33권2호
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• pp.76-80
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• 2020

In this study, vacuum bag hot-press (V-HP) process can be used as an out-of-autoclave (OOA) process by improving the inefficient process of the autoclave forming method with excellent physical properties and surface quality. A carbon fiber composite was molded via V-HP process and analyzed the physical properties and microstructures between composites manufactured by autoclave (AC) process and hot-press process (HP). The tensile strength of the composite materials using the V-HP process was 320.6 MPa and the AC process samples found to be substantially close to the tensile strength of 335.3 MPa. As a result of confirming the surface quality of the composite material using SEM, it was confirmed that in the V-HP process, the removal state of pores due to volatile solvent in the resin was slightly lower than that of the AC process, but it had a considerably superior surface compared to the HP process.

• Composites Research
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• 제31권6호
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• pp.304-310
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• 2018

Autoclave process has been remaining as one of the most robust and stable process in fabricating structural composite part of aerospace industry. It has lots of advantages, however exhibits some disadvantages or limitations in capital investment and operation. Recently, there have been various Out-of-Autoclave process being researched and developed to overcome those limitations. In this study, laminate specimens were fabricated using LCM (Liquid Composite Molding) process, regarded as one of potential OoA process. DB (Double bagging), CAPRI (Controlled Atmospheric Pressure Resin Infusion), VAP (Vacuum Assisted Process) and Autoclave process were used for laminate specimens. Void content, Thickness, Tg (Glass Transition Temperature), ILSS (Interlaminar Shear Strength) and Flexural strength properties were evaluated for comparison. It is verified that Autoclave based specimen has uniform thickness distribution, the lowest void content and outstanding mechanical properties. And, CAPRI based specimen exhibits relatively good physical and mechanical properties over DB and VAP based specimen and comparable mechanical properties with autoclave based specimen.

• Journal of Aerospace System Engineering
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• 제17권2호
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• pp.71-77
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• 2023

Liquid Composite Molding (LCM), an Out of Autoclave (OoA) composite manufacturing process, has big advantages when making large and complex structures of airplanes. Since the importance of LCM process is increasing, FAA has suggested recommended guidance and criteria for the development of material and process specifications for LCM materials and process. The importance of LCM process is also raised by domestic composite material suppliers and OEM. This study suggested structures of material specifications and process specification of LCM materials. Material qualification method for LCM process and material was also developed in this study.

• Composites Research
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• 제34권2호
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• pp.88-95
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• 2021

VARTM (Vacuum-assisted resin transfer molding) process is a low-cost process technology and affiliated with OoA (Out of Autoclave). Besides, it has been widely used in various fields. However, because of its lower quality than the autoclave process, it isn't easy to apply the VARTM process to the aerospace industry, which requires high reliability. The main problem of the VARTM process is the loss of mechanical properties due to the low fiber volume fraction and high void content in comparison to the autoclave. Therefore, many researchers have studied to reduce void and increase fiber volume fraction. This study examines whether the method of controlling atmospheric pressure could increase the fiber volume fraction and reduce void during the resin impregnation process. Reliability evaluation was confirmed by compressive strength test, fiber volume fraction analysis, and optical microscopy. As a result, it was confirmed that increasing the atmospheric pressure step by step in the VARTM process of impregnating the preform with resin effectively increases the fiber volume fraction and reduces void.

• Journal of the Korean Society for Precision Engineering
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• 제17권9호
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• pp.81-86
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• 2000

This paper was carried out to investigate the characteristics of interlaminar fracture toughness of foam core sandwich structures under opening loading mode by using the double cantilever beam (DCB) specimens in Carbon/Epoxy and foam core composites. instead of using symmetric geometry of DCB specimen non-symmetric DCB specimen was used to calculate the interlaminar fracture toughness. Three approaches for calculating the energy release rate({{{{ {G }_{IC } }}}}) were compared. Fracture toughness of foam core sandwich structures by autoclave vacuum bagging and hotpress were compared and analyzed. Experiment nonlinear beam bending FEM method were performed. Suggested bonding surface compensation and equivalent area inertia moment was used to calculate the energy release rate in nonlinear analytical results. The conclusions among experimental nonlinear analytical and FEM results was observed. The vacuum bagging method was shown to be able to substitute method in stead of autoclave without serious loss of Mode I energy release rate({{{{ {G }_{IC }}}}}) to be able to substitute method in stead of autoclave without serious loss of Mode I energy release rate({{{{ {G }_{IC }}}}}).

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.248-253
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• 1997

The study was carried out to evaluate material characteristics and environmental effects of anti-corrosion inhibitor which is known to be very easy to use, since the admixture is added during concrete mixing. Specimens were fabricate with 6 different dosages of anti-corrosion inhibitor and cured in the autoclave chamber with different number of cycles. As a result of measuring corrosion of reinforcing bars embedded in concrete, it was found that even small amount of admixture application can prevent reinforcing bars from corrosion and the efficiency is gradually decreased with increase of the number of autoclave cycles and of percentage of chloride content. In addition, the admixture will not affect material characteristics such as compressive strength and air content.

• Journal of the Korean Ceramic Society
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• 제41권8호
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• pp.582-587
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• 2004

Biphasic Calcium Phosphate (BCP) consisted of hydroxyapatite (HAp) and $\beta$-tricalcium phosphate (P-TCP) has been prepared by solid state reaction. The size reduction of the resultant BCP agglomerate was carried out by reaction with hot water under atmospheric condition uld also under high pressure using an autoclave. The influence of processing conditions on the change of crystalline phase and composition, relative amount of constituent, specific surface area, and microstructure was investigated by means of XRD, FT-IR, BET method using a nitrogen adsorption and SEM.

• Composites Research
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• 제34권4호
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• pp.233-240
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• 2021

VaRI(Vacuum assisted Resin Infusion) process, which is cost effective and suitable for manufacturing large-sized composites, is an OoA(Out-of Autoclave) process. For rapid resin infusion in the VaRI process, a DM(distribution media) is placed on top of the fabric. The resin is rapidly supplied in plane direction of the fiber along the DM, and then the supplied resin is impregnated in the out-of-plane direction of fiber. It is difficult to predict the flow of resin because the flow of in-plane direction and the out-of-plane direction occur together, and a 3D numerical analysis program is used to simulate the resin infusion process. However, in order to analyze in 3D, many elements are required in the out-of-plane direction of fabric. And the product size is larger, the longer the analysis time needs. Therefore, in this study, a method was suggested to reduce the time required for flow analysis by simplifying the 3D flow analysis to 2D flow analysis. The usefulness was verified by comparing the 3D flow analysis with the simplified 2D flow analysis at the same conditions. The filling time error was about 7% and the reduction of flow analysis time was about 95%. In addition, by utilizing the constant difference in the flow front between the top, middle, and bottom of the fabric of the 3D analysis, the flow front of the top, middle, and bottom of the fabric can be also predicted in the 2D flow analysis.

• Journal of the Korean Wood Science and Technology
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• 제25권3호
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• pp.37-42
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• 1997

This study was carried out to track the heated-air flows within the tree disk through measuring the distribution of wood temperatures during explosing the 7.5mm-thick Japanese cedar disk and to investigate the effects of the time for the first explosion cycle and the number of explosion cycles on the improvement of permeability of tree disk. If the tree disk are explosed when the temperatures of the shell and core of it are not equilibrium yet, all of the inflated airs in the shell after explosion don't flow out toward the autoclave and some of them flow into the core of which the air pressures are lower than those of the shell. It is very effective for the improvement of permeability of tree disk to make the first explosion cycle when the temperatures of the shell and the core equilibrate at the setting temperature of steam in the autoclave. The more tree disks were explosed under the same conditions of first explosion, the more their permeabilities were improved.