• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2386-2395
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• 1994

An experimental study on heat transfer and flow in compression molding of clss-B and A SMC(Sheet Molding Compounds) in a flat plate and a cross-sectional T-shape was carried out. The temperature was measured with thermocouples at two locations in the 4 layered SMC charge and pressure was measured at the center of the top mold during compression molding. Three different mold speeds, 15, 45, 50 mm/min and two different mold temperature, $130^{\circ}C{\;}and{\;}150^{\circ}C$ were used for compression molding experiments. Experiments with different colored SMC layers were used to study flow patterns at various compression stages. In oder to predict the pressure and load in SMC compression molding, slab method was used. The predicted values of pressure and load from the slab analysis were compared well with the measured data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.1
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• pp.154-163
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• 1997

Thermally-induced deformation in SMC(Sheet Molding Compound) products is analyzed using three dimensional finite element method. Planar fiber orientation, which causes the anisotropic material properties, is calculated through the flow analysis during the compression stage of the mold. Also curing process is analyzed to predict temperature profile which has significant effects on warpage of SMC products. Through the developed procedure, effects of various process conditions such as charge location, mold temperature, fiber contents, and fiber orientations on deformation of final products are studied. and processing strategies are proposed to reduce the warpage and the shrinkage.

• Transactions of Materials Processing
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• v.4 no.1
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• pp.39-47
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• 1995

The compression molding of SMC (sheet molding compund) at room temperature was analyzed based on rigid-viscoplastic approach by three dimensional finite element program. The developed program was tested by solving the three dimensional compression of wedge type specimens of aluminum alloys at various processing conditions. The simulation results were compared well to the experimental results available in the literature. based on this comparison the program was proved to be valid and was further applied in solving compression molding of SMC, which is a thermosetting material reinforced with chopped fiber glass. To investigate the effects of friction conditions and mold closing speeds for compression molding of SMC charge at room temperature, compressions of the cylindrical and rectangular shaped SMC were analyzed for various friction conditions and mold closing speeds. The calculated load values were compared to the experimental results for the compression molding of cylindrical specimen.

• Transactions of Materials Processing
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• v.4 no.3
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• pp.204-213
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• 1995

A finite element program is developed to analyze the flow phenomena in SMC compression molding as a viscoplastic model. The calculation of temperature distribution is also carried out by uncoupling the thermal analysis from the flow analysis. SMC molding processes with a flat plate substructure and the one with a T-shaped rib are considered in numerical simulation. The numerical results provide deformed shapes, temperature distribution in a SMC charge, and the forming load. The simulation of compression molding of a flat plate with a T-shaped rib requires a remeshing technique for the whole process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.2
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• pp.488-499
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• 1996

SMC(Sheet molding compound) is a thermosetting material reinforced with chopped fiberglass. The compression molding of SMC was analyzed based on a rigid thermo-viscoplastic approach using a three dimensional finite element program coupled with temperatures. Only the temperature analysis part was tested in this paper by solving one-dimensional heat transfer problem and comparing with the exact solutions available in the literature. Based on this comparison the program was proved to be valid and was further applied in solving compression molding of SMC between flat dies. To investigate the usefulness of a rigid thermo-viscoplastic approach in the compression molding analysis of SMC charge, compression of rectangular shaped SMC charge at plane strain and three dimensionalde formation condition was analyzed under the same condition as given in the literature. From this comparison it was found out that the rigid thermo-viscoplastic approach was useful in analyzing SMC compression molding between flat dies.

• Journal of the korean Society of Automotive Engineers
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• v.18 no.5
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• pp.96-120
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• 1996

현재 자동차용 복합재료를 생산하는데 유리한 제조방법으로는 압축성형 (Compression Molding), 액상성형(Liquid Molding), 인발성형(Pultrusion), 필라멘트 와인딩성형(Filament Winding)등이 있다. 압축성형은 현재 자동차 외장부품 성형에 널리 알려져 있는 SMC(Sheet Molding Compound)성형, 최근에 많은 연구가 되고 있는 LMPC(Low Pressure Molding Compound)성형, GMT(Glass Mat Reinforced Thermoplastics)성형 등이 있다. 액상성형은 RTM(Resin Transfer Molding)과 VARI (Vacuum Assisted Injection Molding), SRIM(Structure Reaction Injection Molding) 등이 있으며, 자동차 산업뿐만 아니라 일반 산업에서도 최근 많은 각광을 받고 있다. 그러므로 본 소고에서는 자동차용 복합재료의 제조에 널리 사용되는 성형공정에 대하여 간단히 살펴보고, 자동차 부품에 있어서의 복합재료 응용 현장과 최근 환경문제가 대두되면서 관심의 초점이 되고 있는 자동차용 복합재료 재활용 기술에 대하여 고찰하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.79-87
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• 1996

SMC(Sheet Molding Compound) is made of unsaturated polyester resin and other additives reinforced with randomly distributed chopped fiberglass strands. Because of its higher stiffness per unit mass, SMC was used as a substitute for steel for automotive steel outer panels. Thus, understanding of flow characteristics during fabrication of SMC is of importance since the formation of weld line depends on material flow. In the present study, SMC compression molding simulations in the flat and T-shape molds were accomplished. During simulations, the preferential the preferential flow occurred at the low mold closing speed while plug flow was observed for the higher mold closing speed. When the preferential flow was observed, the weld line was seen at the final stage. For simulations, rigid-viscoplastic finite element method was applied. Self-contact algorithm was also applied in order to predict the formation of the weld line. Simulation results were compared to the experimental results available in the literature.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.3084-3090
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• 1994

A new flow model is developed for the analysis of compression molding of sheet molding compounds(SMC) and penalty finite element formulation is presented to predict flow front progressions more accurately. In this model SMC is assumed nonisothermal fluid, which has different viscosities in extension and in shear. The flow is allowed to slip at the mold and is resisted by friction force which is proportional to the relative velocity at mold surface. For the verification of the model, the press force and flow patterns are compared with those of experiments and available results by other works in this field. It is also demonstrated, using the computational procedure described and the proposed model, that optimal initial charge shapes for the filling can be effectively computed.

• Tribology and Lubricants
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• v.18 no.5
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• pp.345-350
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• 2002

Recently, as the development of manufacturing technique on SMC(sheet molding compound), various numerical and experimental approaches to injection and compression molding have been investigated. Injection and compression molding, however, has so various cases with complicated boundary condition that it is difficult to analyze mold characteristics precisely. In addition, since a slight change in process variables can significantly change the resulting mold thickness, a proper design is important to compression molding process. Therefore, in this study, the effects of various parameters on compression molding process have been investigated using FEM(finite element method) to formulate the melt front advancement during the mold filling process. To verify the results of present analysis, they are compared with those of reference. The results show a strong effect of initial charge volume, injection time and pressure as a result of variations in the rectangular charge shape.