The Experts below are selected from a list of 8142 Experts worldwide ranked by ideXlab platform
H.t. Hahn - One of the best experts on this subject based on the ideXlab platform.
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analysis of vacuum bag resin Transfer Molding process
Composites Part A-applied Science and Manufacturing, 2001Co-Authors: M. K. Kang, H.t. HahnAbstract:An analytical model is developed to analyze the resin flow through a deformable fiber preform during vacuum bag resin Transfer Molding (VBRTM) process. The force balance between the resin and the fiber preform is used to account for the swelling of fiber preform inside a flexible vacuum bag. Mold filling through multiple resin inlets is analyzed under different vacuum conditions. The formation of dry spots is demonstrated in the presence of residual air. Molding of a three-dimensional ship hull with lateral and longitudinal stiffeners is simulated to demonstrate the applicability of the model.
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Resin Transfer Molding process optimization
Composites Part A: Applied Science and Manufacturing, 2000Co-Authors: Mark Y. Lin, M J Murphy, H.t. HahnAbstract:The art of process optimization requires a clear understanding of the differences between each of the widely different optimization strategies available. Often, a sophisticated method that has been well tested in other fields is not applicable at all to problems in resin Transfer Molding (RTM). This work discusses the strength and weakness of the genetic algorithm and the gradient based algorithms. Two different types of RTM process optimization have been documented. In the first case, gate locations are optimized to minimize the fill time. The optimum design variables were located using the quasi-Newtonian method implemented in the code GLO. In the second case, the permeability of the high permeability layers is varied to minimize resin waste in addition to minimizing the fill time. For this problem, a graphical search was used to locate the optimum design.
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Analysis of Resin Transfer Molding With High Permeability Layers
Journal of Manufacturing Science and Engineering-transactions of The Asme, 1998Co-Authors: M. J. Tari, Mark Y. Lin, J. P. Imbert, Adrienne S. Lavine, H.t. HahnAbstract:In resin Transfer Molding (RTM) a high permeability layer (HPL) is placed on top of the fiber mat lay-up to reduce mold filling time and increase the ultimate distance resin can be drawn into the mold. HPL's are particularly useful in vacuum bag resin Transfer Molding (VBRTM), where driving pressures are relatively low. When compared to traditional closed mold RTM, VBRTM has the advantages of low capital costs and short start up time. The goal of the current research is to investigate how an HPL can be used to improve quality and process efficiency for parts of complex geometry made by both conventional and vacuum bag RTM. As a first step towards this goal, the effect of the HPL on the flow field has been studied through analysis, experiment and simulation. As expected, the use of the HPL creates a transverse (i.e., top-to-bottom) flow in the fiber mat, facilitating mold filling. The thickness of the HPL has been varied to determine the effects on the flow front. The experimental results validate the capability of the simulation to model two-dimensional flow in a porous medium with heterogeneous permeability.
Suresh G. Advani - One of the best experts on this subject based on the ideXlab platform.
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Comparison of in-plane resin Transfer Molding and vacuum-assisted resin Transfer Molding ‘effective’ permeabilities based on mold filling experiments and simulations:
Journal of Reinforced Plastics and Composites, 2019Co-Authors: Mert Hancioglu, E. Murat Sozer, Suresh G. AdvaniAbstract:Resin Transfer Molding and vacuum-assisted resin Transfer Molding are two of the most commonly used liquid composite Molding processes. For resin Transfer Molding, mold filling simulations can pred...
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Simulating three-dimensional flow in compression resin Transfer Molding process
Revue Européenne des Éléments Finis, 2012Co-Authors: Pavel Simacek, Suresh G. AdvaniAbstract:Compression Resin Transfer Molding (CRTM) is a novel variation of traditional Resin Transfer Molding (RTM). It combines features of RTM, with those of traditional compression Molding. The resin is introduced in the mold containing the preform in the narrow gap between the mold platen and the preform. As the resin flows in the narrow gap between mold and the preform, the mold platen squeezes the resin into the stationary preform, which also undergoes compression to create the desired fiber volume fraction. The flow field exhibits a three-dimensional character and is coupled with the fiber compression dynamics. We have modified our existing resin Transfer mold filling simulation based on flow through porous media to model the resin injection in CRTM.
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process analysis of compression resin Transfer Molding
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Justi Merotte, Pavel Simacek, Suresh G. AdvaniAbstract:Compression resin Transfer Molding process (CRTM) combines features of compression Molding with traditional Resin Transfer Molding (RTM). The CRTM process is described in three stages, with resin being injected into the gap in Stage I, closing of the gap in Stage II and actual compression of preform and re-distribution of the resin in Stage III. To fabricate a void free part, one has to understand the resin flow during these stages. Governing equations for each stage are formulated, relevant non-dimensional parameters are derived and brief description of the numerical model is presented. Assembling the process parameters into non-dimensional groups significantly reduces the number of variables to be explored in the process. The paper analyzes the impact of the dimensional less parameters on impregnation time with the numerical process model. The results show that the impact of many parameters on process speeds is negligible, identifying two non-dimensional parameters that influence the resin injection.
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Modeling flow in compression resin Transfer Molding for manufacturing of complex lightweight high-performance automotive parts
Journal of Composite Materials, 2008Co-Authors: Pavel Simacek, Suresh G. Advani, STANLEY A IOBSTAbstract:Lightweight vehicles for energy savings encourages the use of composites in the new generation of vehicles. The compression resin Transfer Molding process (CRTM) is a novel variation of liquid composite Molding (LCM) which offers fast manufacturing cycle for net-shape complex parts with excellent performance, ideal for the automotive industry. The process combines features of resin Transfer Molding (RTM) and compression Molding. The process stages are identified and compared to other LCM processes to take advantage of existing simulation tools. A numerical model that simulates the resin flow in this process is proposed. Several first-order analyses are developed to estimate important process parameters to simplify modeling. Finally, this approach is used to model and simulate the process and is applied to a complex automotive part ( the Automotive Composites Consortium B-pillar) with qualitative experimental validation.
Chih-yuan Chang - One of the best experts on this subject based on the ideXlab platform.
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Modeling and evaluation of the filling process of vacuum-assisted compression resin Transfer Molding
Journal of Polymer Engineering, 2013Co-Authors: Chih-yuan ChangAbstract:Abstract In the present study, a modified vacuum-assisted compression resin Transfer Molding (VACRTM) process has been developed to reduce the cycling period. The process uses an elastic bag placed between the upper mold and the preform to replace the mobile rigid mold in compression resin Transfer Molding. During resin injection, the bag is pulled upward by the vacuum applied in between the upper mold and the bag, and a loose fiber stack is then present. Resin is easily injected into the mold. Once enough volume of resin is injected, the compression pressure is applied on the bag, which compacts the preform and drives the resin through the remaining dry preform. Numerical results show that the bag compression phase is much longer than the resin injection one. A multistage compression strategy can be used to control the compression time. Due to inherent process defects, a higher volume of the injected liquid is essential and thus leads to a longer injection and compression phase in order to inject and squeeze the excess resin. The late compression is very slow in draining the residual resin. As compared with resin Transfer Molding, VACRTM can reduce the mold-filling time/injection pressure.
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Experimental analysis of mold filling in vacuum assisted compression resin Transfer Molding
Journal of Reinforced Plastics and Composites, 2012Co-Authors: Chih-yuan ChangAbstract:Vacuum-assisted compression resin Transfer Molding, a flexible resin Transfer Molding process, has been developed to reduce a cycling period in the present study. The vacuum-assisted compression re...
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Simulation of Compression Effect on Filling Process in Compression Resin Transfer Molding
Advanced Composite Materials, 2011Co-Authors: Chih-yuan ChangAbstract:The compression resin Transfer Molding (CRTM) filling process involves two stages: the injection phase and the compression phase. Two injection modes are considered — constant volumetric flow rate and constant pressure — while the constant compression velocity is utilized in this study. Three typical cases are used to investigate the compression initiation effects on the filling process. When the inlet condition is a constant flow rate, the numerical results show that the compression has both increase and decrease effects on the inlet pressure. Thus, a discontinuity in the inlet pressure is present at the onset or the end of compression. Among three CRTM cases, the process with a simultaneous injection and compression end maximally reduces the inlet pressure by 80% but increases the mold filling time by 65% compared with the resin Transfer Molding (RTM). For the inlet condition being a constant pressure, the resin may flow out of the mold cavity through the inlet when an excessively low injection pressure...
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Effect of Process Variables on the Quality of Compression Resin Transfer Molding
Journal of Reinforced Plastics and Composites, 2006Co-Authors: Chih-yuan Chang, Lih-wu Hourng, Tsung-yi ChouAbstract:Compression resin Transfer Molding (CRTM), combining resin Transfer Molding (RTM) and compression Molding, have been developed to fabricate fiber reinforced plastic (FRP) components with large dime...
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A novel method for rapid fabrication of microlens arrays using micro-Transfer Molding with soft mold
Journal of Micromechanics and Microengineering, 2006Co-Authors: Chih-yuan Chang, Sen-yeu Yang, Long-sun Huang, Tian-ming JengAbstract:This paper reports a novel technique for fabricating polymeric microlens arrays based on micro-Transfer Molding with soft mold. The soft mold with a micro-holes array is made by casting a pre-polymer of PDMS against a silicon master. The silicon master of the micro-cylinders array is prepared using photolithography and deep reactive ion etching. During the micro-Transfer Molding operation, the surface of the soft mold of the micro-holes array is filled with liquid UV curable photopolymer, and the soft mold is then pressed against the flat substrate with a slight pressure for a period of time. After the soft mold is removed from the substrate, surface tension causes the liquid photopolymer cylinders to assume a spherical shape. Finally, the liquid photopolymer is cured by UV irradiation at room temperature. A substrate with a microlens array pattern can be successfully fabricated. In this study, a micro-Transfer Molding facility with UV exposure capacity has been designed, constructed and tested. The 100 × 100 arrays of a polymeric microlens have been successfully produced. Under the condition of 50 kPa stamping pressure, 6 s duration and 500 mJ cm−2 UV curing dose, the microlenses were successfully formed on the plastic substrate. Their optical properties were verified with a beam profiler. In addition, microlenses of different curvatures and focal lengths can be obtained by using substrates with different surface wettabilities. This study shows that micro-Transfer Molding can be used for the fabrication of polymeric microlens arrays with high productivity and low cost.
Mark Y. Lin - One of the best experts on this subject based on the ideXlab platform.
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Resin Transfer Molding process optimization
Composites Part A: Applied Science and Manufacturing, 2000Co-Authors: Mark Y. Lin, M J Murphy, H.t. HahnAbstract:The art of process optimization requires a clear understanding of the differences between each of the widely different optimization strategies available. Often, a sophisticated method that has been well tested in other fields is not applicable at all to problems in resin Transfer Molding (RTM). This work discusses the strength and weakness of the genetic algorithm and the gradient based algorithms. Two different types of RTM process optimization have been documented. In the first case, gate locations are optimized to minimize the fill time. The optimum design variables were located using the quasi-Newtonian method implemented in the code GLO. In the second case, the permeability of the high permeability layers is varied to minimize resin waste in addition to minimizing the fill time. For this problem, a graphical search was used to locate the optimum design.
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Analysis of Resin Transfer Molding With High Permeability Layers
Journal of Manufacturing Science and Engineering-transactions of The Asme, 1998Co-Authors: M. J. Tari, Mark Y. Lin, J. P. Imbert, Adrienne S. Lavine, H.t. HahnAbstract:In resin Transfer Molding (RTM) a high permeability layer (HPL) is placed on top of the fiber mat lay-up to reduce mold filling time and increase the ultimate distance resin can be drawn into the mold. HPL's are particularly useful in vacuum bag resin Transfer Molding (VBRTM), where driving pressures are relatively low. When compared to traditional closed mold RTM, VBRTM has the advantages of low capital costs and short start up time. The goal of the current research is to investigate how an HPL can be used to improve quality and process efficiency for parts of complex geometry made by both conventional and vacuum bag RTM. As a first step towards this goal, the effect of the HPL on the flow field has been studied through analysis, experiment and simulation. As expected, the use of the HPL creates a transverse (i.e., top-to-bottom) flow in the fiber mat, facilitating mold filling. The thickness of the HPL has been varied to determine the effects on the flow front. The experimental results validate the capability of the simulation to model two-dimensional flow in a porous medium with heterogeneous permeability.
Pavel Simacek - One of the best experts on this subject based on the ideXlab platform.
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Simulating three-dimensional flow in compression resin Transfer Molding process
Revue Européenne des Éléments Finis, 2012Co-Authors: Pavel Simacek, Suresh G. AdvaniAbstract:Compression Resin Transfer Molding (CRTM) is a novel variation of traditional Resin Transfer Molding (RTM). It combines features of RTM, with those of traditional compression Molding. The resin is introduced in the mold containing the preform in the narrow gap between the mold platen and the preform. As the resin flows in the narrow gap between mold and the preform, the mold platen squeezes the resin into the stationary preform, which also undergoes compression to create the desired fiber volume fraction. The flow field exhibits a three-dimensional character and is coupled with the fiber compression dynamics. We have modified our existing resin Transfer mold filling simulation based on flow through porous media to model the resin injection in CRTM.
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process analysis of compression resin Transfer Molding
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Justi Merotte, Pavel Simacek, Suresh G. AdvaniAbstract:Compression resin Transfer Molding process (CRTM) combines features of compression Molding with traditional Resin Transfer Molding (RTM). The CRTM process is described in three stages, with resin being injected into the gap in Stage I, closing of the gap in Stage II and actual compression of preform and re-distribution of the resin in Stage III. To fabricate a void free part, one has to understand the resin flow during these stages. Governing equations for each stage are formulated, relevant non-dimensional parameters are derived and brief description of the numerical model is presented. Assembling the process parameters into non-dimensional groups significantly reduces the number of variables to be explored in the process. The paper analyzes the impact of the dimensional less parameters on impregnation time with the numerical process model. The results show that the impact of many parameters on process speeds is negligible, identifying two non-dimensional parameters that influence the resin injection.
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Modeling flow in compression resin Transfer Molding for manufacturing of complex lightweight high-performance automotive parts
Journal of Composite Materials, 2008Co-Authors: Pavel Simacek, Suresh G. Advani, STANLEY A IOBSTAbstract:Lightweight vehicles for energy savings encourages the use of composites in the new generation of vehicles. The compression resin Transfer Molding process (CRTM) is a novel variation of liquid composite Molding (LCM) which offers fast manufacturing cycle for net-shape complex parts with excellent performance, ideal for the automotive industry. The process combines features of resin Transfer Molding (RTM) and compression Molding. The process stages are identified and compared to other LCM processes to take advantage of existing simulation tools. A numerical model that simulates the resin flow in this process is proposed. Several first-order analyses are developed to estimate important process parameters to simplify modeling. Finally, this approach is used to model and simulate the process and is applied to a complex automotive part ( the Automotive Composites Consortium B-pillar) with qualitative experimental validation.
