Chung Hae PARK - Academia.edu (original) (raw)

Papers by Chung Hae PARK

Research paper thumbnail of Multiconstraint Optimization of Composite Structures Manufactured by Resin Transfer Molding Process

Journal of Composite Materials, 2005

A simultaneous optimization methodology is proposed considering both the structural and the proce... more A simultaneous optimization methodology is proposed considering both the structural and the process requirements for the weight minimization of laminated plates manufactured by the Resin Transfer Molding (RTM) process. The coupling between the structural performance and the process cost is considered through the investigation of state parameters in the RTM process. As the structural constraint, maximum allowable displacement or maximum allowable failure index of the structure under load is assigned. For the process constraint, maximum allowable mold filling time is given. A new approach to deal with design constraints without having to concern about the penalty parameters is suggested. The influence of design constraints on the optimal design configuration is investigated through parametric studies. As the optimization scheme, Genetic Algorithm (GA) is employed. To take into account the layer number variation, genetic operators such as the crossover and the mutation are modified.

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Research paper thumbnail of Analytical modeling and in situ measurement of void formation in liquid composite molding processes

Advanced Composite Materials, 2014

ABSTRACT Liquid composite molding processes are widely accepted in the aeronautic industry to man... more ABSTRACT Liquid composite molding processes are widely accepted in the aeronautic industry to manufacture large and complex structural parts. In spite of their cost-effectiveness, void defects created during the manufacturing process are a major issue of these processing techniques because they have detrimental effects on the mechanical performance. The reliable modeling is still a difficult task and experimental observations are usually adopted for the analysis of void formation mechanism, however, because many different physics are simultaneously involved during the mold filling process and the resin curing process. The complexity of the void formation physics implies the need for an in situ measurement of void formation not in the final part but in the mold filling procedure during the manufacturing process to better understand the void mechanism. In this regard, we present a sensor system measuring the electric conductivity for the in situ monitoring of void formation during the mold filling process. We also propose a theoretical model to predict void formation in a quantitative way with the properties of the resin and the fiber reinforcement. The model prediction is compared with the experimental data obtained by the sensor system to validate the model.

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Research paper thumbnail of Integrated optimization for weight, performance and cost of composite structures

Information Control Problems in Manufacturing 2006, 2006

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Research paper thumbnail of Integrated optimization for weight, performance and cost of composite structures

Information Control Problems in Manufacturing 2006, 2006

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Research paper thumbnail of Unsaturated and saturated permeabilities of fiber reinforcement: critics and suggestions

Frontier in Materials, 2015

In general, permeability measurement results show a strong scattering according to the measuremen... more In general, permeability measurement results show a strong scattering according to the measurement method, the type of test fluid and the fluid injection condition, even though permeability is regarded as a unique property of porous medium. In particular, the discrepancy between the unsaturated and saturated permeabilities for the same fabric has been widely reported. In the literature, relative permeability has been adopted to model the unsaturated flow. This approach has some limits in the modeling of double-scale porosity medium. We address this issue of permeability measurement by rigorously examining the mass conservation condition. Finally, we identify that the pressure gradient is non-linear with positive curvature in the unsaturated flow and a misinterpretation of pressure gradient is the main reason for the difference between the saturated and unsaturated permeabilities of the same fiber reinforcement. We propose to use a fixed value of permeability and to modify the mass conservation equation if there are air voids, which are entrapped inside the fiber tow. Finally, we also suggest some guidelines and future perspectives to obtain more consistent permeability measurement results.

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Research paper thumbnail of Multiconstraint Optimization of Composite Structures Manufactured by Resin Transfer Molding Process

Journal of Composite Materials, 2005

A simultaneous optimization methodology is proposed considering both the structural and the proce... more A simultaneous optimization methodology is proposed considering both the structural and the process requirements for the weight minimization of laminated plates manufactured by the Resin Transfer Molding (RTM) process. The coupling between the structural performance and the process cost is considered through the investigation of state parameters in the RTM process. As the structural constraint, maximum allowable displacement or maximum allowable failure index of the structure under load is assigned. For the process constraint, maximum allowable mold filling time is given. A new approach to deal with design constraints without having to concern about the penalty parameters is suggested. The influence of design constraints on the optimal design configuration is investigated through parametric studies. As the optimization scheme, Genetic Algorithm (GA) is employed. To take into account the layer number variation, genetic operators such as the crossover and the mutation are modified.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Analytical modeling and in situ measurement of void formation in liquid composite molding processes

Advanced Composite Materials, 2014

ABSTRACT Liquid composite molding processes are widely accepted in the aeronautic industry to man... more ABSTRACT Liquid composite molding processes are widely accepted in the aeronautic industry to manufacture large and complex structural parts. In spite of their cost-effectiveness, void defects created during the manufacturing process are a major issue of these processing techniques because they have detrimental effects on the mechanical performance. The reliable modeling is still a difficult task and experimental observations are usually adopted for the analysis of void formation mechanism, however, because many different physics are simultaneously involved during the mold filling process and the resin curing process. The complexity of the void formation physics implies the need for an in situ measurement of void formation not in the final part but in the mold filling procedure during the manufacturing process to better understand the void mechanism. In this regard, we present a sensor system measuring the electric conductivity for the in situ monitoring of void formation during the mold filling process. We also propose a theoretical model to predict void formation in a quantitative way with the properties of the resin and the fiber reinforcement. The model prediction is compared with the experimental data obtained by the sensor system to validate the model.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Integrated optimization for weight, performance and cost of composite structures

Information Control Problems in Manufacturing 2006, 2006

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Integrated optimization for weight, performance and cost of composite structures

Information Control Problems in Manufacturing 2006, 2006

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Unsaturated and saturated permeabilities of fiber reinforcement: critics and suggestions

Frontier in Materials, 2015

In general, permeability measurement results show a strong scattering according to the measuremen... more In general, permeability measurement results show a strong scattering according to the measurement method, the type of test fluid and the fluid injection condition, even though permeability is regarded as a unique property of porous medium. In particular, the discrepancy between the unsaturated and saturated permeabilities for the same fabric has been widely reported. In the literature, relative permeability has been adopted to model the unsaturated flow. This approach has some limits in the modeling of double-scale porosity medium. We address this issue of permeability measurement by rigorously examining the mass conservation condition. Finally, we identify that the pressure gradient is non-linear with positive curvature in the unsaturated flow and a misinterpretation of pressure gradient is the main reason for the difference between the saturated and unsaturated permeabilities of the same fiber reinforcement. We propose to use a fixed value of permeability and to modify the mass conservation equation if there are air voids, which are entrapped inside the fiber tow. Finally, we also suggest some guidelines and future perspectives to obtain more consistent permeability measurement results.

Bookmarks Related papers MentionsView impact