• 한국정밀공학회지
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• 제15권7호
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• pp.85-90
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• 1998

The business of manufacturing is increasingly becoming time-compressing, precise and long-life oriented, owing to various needs from the consumers and harsh global competition. With the emergence of the layer laminate manufacturing method, it is possible to produce prototypes directly from 3D CAD and additive process, the production time and cost have shortened dramatically. However there are some problems like surface-step, dimensional deviation and warp. A newly developed powder casting is suitable for rapid-manufacturing metallic tools. Powder casting can serve as a promising rapid tooling method because of high density characteristics and low dimensional shrinkage below 0.1％ during sintering and infiltration. By this process, we have realized significant time savings bypassing the wait for prototype tooling and cost savings eliminating the expense of conventional prototype tooling process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.191-194
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• 1995

The business of manufacturing is increasingly becomeing time-compresssing, precise and long-life oiented, owing to various needs form the consumers and harsh global competition. with the emergence of the layer laminate maunfacturing methods, it is possible to prototypes directly from 3D CAD and additive process, the production time and cost have shortened dramatically. However there are some problems like surface-step, dimensional deviation and warp. A newly developed powder casting is suitable for rapid-manufacturing metallic tools. Powder casting can serve as a promising repid tooling method because of high density charateristics and low dimensional shrinkage below 0.1% during sintering and infiltration. By this process, we have realized significant time savings bypassing the wait for prototype tooling and cost savings eliminating the expense of conventional prototype tooling process.

• 한국기계가공학회지
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• 제18권3호
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• pp.66-73
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• 2019

Recently, FDM-type 3D printer technology has been developed, and efforts have been made to improve the output formability and characteristics further. Through this, 3D printers are used in various fields, and printer technologies are suggested according to usage, such as FDM, SLA, DLP, and SLM. In particular, the FDM method is the most widely used, and the FDM method technology is being developed further. The characteristics of the output are produced by the FDM-type 3D printer, which is determined by various factors, and particularly the perspective of the Inter-Layer Fill Factor, which is the volume ratio of the laminated material that exerts a direct influence. In this study, the Inter-Layer Fill Factor is theoretically obtained by presenting the internal space between each layer according to the laminate thickness as a cross-sectional shape model, and the cross section of the actual laminated sample is compared with the theoretical model through experiments. Then, the equation for the theoretical model is defined, and the strength change according to each condition (tensile strength of material, reduction slope, strength reduction rate, and output strength) is confirmed. In addition, we investigated the influence on the correlation and strength between laminate thickness and the Inter-Layer Fill Factor.

• 한국공작기계학회논문집
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• 제12권4호
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• pp.43-49
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• 2003

This research work has been carried out for finding J-integral in mode II of CFRP(carbon fiber reinforced plastics) laminate plates based on the classical bar theory in dynamic conditions with consideration of the effect of inertia forces, eventually to lead to finding the dynamic inter-layer fracture toughness. Dynamic inter-layer fracture toughness was found by a self-made ENF(End Notched Flexure) experimental apparatus using Split Hopkinson's Bar(SHPB), and also observed the variation of the fracture toughness haying different resin contents and fiber arrangements of CFRP specimen([$0_3^{\circ}/90_3^{\circ}/0_6^{\circ}/90_3^{\circ}/0_3^{\circ}$], [$0_{20}^{\circ}$], [$0_5^{\circ}/90_{10}^{\circ}/0_5^{\circ}$]). As an experimental result, in either cases of quasi-static or dynamic load condition, the critical load and the inter-layer fracture toughness increased sharply depending on the increase of resin contents. Therefore, it could, be concluded that the effect by resin contents is the major factor determining the inter-layer fracture toughness in the CFRP laminate plates.

• 대한안전경영과학회지
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• 제25권1호
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• pp.23-29
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• 2023

Among the Additive Manufacturing (AM) technologies, the Binder-Jetting printing technology is a method of spraying an adhesive on the surface of powder and laminate layer by layer. Recently, this technique has become a major issue in the production of large casting products such as ship-building, custom vehicles and so on. In this study, we performed research to make actual mold castings and increase mechanical property by using special sand and water-based binders. For use as a mold, it has a strength of more than 3MPa and permeability. Various experiments were carried out to obtain suitable them. The major process parameters were binder jetting volume, binder types, layer thickness and heat treatment condition. As a result of this study, the binder drop quantity was measured to be about 60 pico-liter, layer thickness was 100㎛ and the heat treatment condition was measured about 1,000℃ and compressive strength were measured to be more than 5MPa. The optimum condition of this experiment was established through actual casting of aluminum. The equipment used in this study was a Freeforms T400 model (SFS Co., Ltd.), and the printing area of 420 * 300 * 250mm and resolution of 600dpi can be realized.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1514-1519
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• 2001

This paper is concerned with design, manufacturing and performance test of LIPCA ( Lightweight Piezo- composite Curved Actuator) using a top carbon fiber composite layer with near -zero CTE(coefficient of thermal expansion), a middle PZT ceramic wafer and a bottom glass/epoxy layer with high CTE. The main point of this design is to replace the heavy metal layers of THUNDER by thigh tweight fiber reinforced plastic layers without losing capabilities to generate high force and large displacement. It is possible to save weight up to about 30% if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a graphite/epoxy prepreg were simply stacked and cured at an elevated temperature (177 $^{circ}C$ after following an autoclave bagging process. It was found that the manufactured composite laminate device had a sufficient curvature after detached from a flat mold. The analysis method of the cure curvature of LIPCA using the classical lamination theory is presented. The predicted curvatures are fairly in agreement with the experimental ones. In order to investigate the merits of LIPCA, a performance test of both LIPCA and THUNDE$^{TM}$ were conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDERT$^{TM}$.

• 한국기계가공학회지
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• 제6권3호
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• pp.77-84
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• 2007

As a life cycle of product bas shortend, Rapid prototypiug has come into the spotlight to shortened the time of producint a prototype. But It followed in laminated directivity and of the prototype production which is decided the interference which Beccuase of invisible rough surface, some inferences have occured during an assembly hour. Consequently, This study on rapid prototyping has parameter to determine surface roughness and surface form precision of total shape. In order to improve Surface form precision, it can control parameters which are Laminate Height, Layer Hatch Overcue, Fill Cure Depth. In addition, we found the parameter which have a deep effect on surface roughness among various parameters, and then, tried to reduce the interference that can be occurred by surface roughness during assembly.

• 한국진공학회지
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• 제6권S1호
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• pp.80-88
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• 1997

The attempt to enhance the strength of materials has been an important subject for materials engineering and scientists. The strength of materials is termed as the ability to support high load without excessive deformation and without breaking catastrophically. The control of dislocation densities and barriers to the movement of dislocations have been considered to be the important methods for the strengthening materials. One of the approaches is mechanical blocking of dislocations by alternately depositing material layers. The typical structure of materials is multilayered and laminated composites. The thickness of each layer is typically in the range of nanometer. Ton avoid confusion with other terminology they may be defined as microlaminate composite materials. The manufacturing process of multilayered laminate structure will be introduced. And the current theoretical theories will be reviewed in view of strengthening of microlaminte composite materials.

• Composites Research
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• 제29권5호
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• pp.249-255
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• 2016

섬유금속적층판은 우수한 피로특성, 내부식성, 충격저항 등으로 인하여 항공우주산업에서 널리 사용되고 있다. 본 논문에서는 다구찌 기법을 사용하여 섬유금속적층판의 내부 에너지 해방률을 향상시킬 수 있는 공정 조건을 도출하는 절차에 대해 실험적 연구가 수행되었다. 내부 접착력 향상을 위한 제조공정을 도출하기 위해서, 표면처리, 접착필름의 용융점 유지시간 및 초기 압력이 서로 다르다는 조건하에서 제작한 시편들에 대해서 Double cantilever beam과 End-notched flexure 시험을 수행하였다. 시험으로부터 모드 I과 모드 II의 에너지 해방률을 측정한 후, 다구찌 기법의 망대특성에 의한 신호 잡음비를 비교하여 효율적인 제조공정을 도출하였다.

• 한국공작기계학회논문집
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• 제10권6호
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• pp.48-56
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• 2001

In this paper, this study aims at the evaluation on the characteristics of CFRP laminate plates using a falling weight impact tester. The experiment was conducted on several laminates of different orientation. A system was built far measur- ing the impact strength of CFRP laminates in consideration of stress wave propagation theory using a falling weight impact tester. Delamination areas of impacted specimens for the different ply orientation were measured with ultrasonic C- scanner to find correlation between impact energy and delamination area. Absorbed energy of quasi-isotropic specimen having flour interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the greater the energy absorbed. The absorbed energy oft hybrid specimen containing a GFRP layer was higher than that of normal specimens.