Navegando por Autor "Amico, Sandro Campos"

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Algebraic rectilinear model for multilayer resin transfer molding injection
(2013) Oliveira, Cristiano Peres; Souza, Jeferson Avila; Isoldi, Liércio André; Amico, Sandro Campos
An analytical model for the multilayer rectilinear injection applied to the RTM process has been developed. The model takes into account the permeability in both in-plane (Kxx and Kyy ) and transverse (Kzz ) directions of each layer of the reinforcement media and calculates the transverse permeability (Kt ) through adjacent layers. Porosity and thickness are set independent for each layer of the assembly. Mass balance of resin within the layers is used to develop an expression that estimates resin position (xi ) as a function of time (t) independently of each layer. The resulting equation was solved using: (i) Numerical integration and (ii) algebraic integration of the simplified expression resulting in a closed expression for x i = xi (t). Results of both proposed methods were compared with the calculations performed using the PAM-RTM software for cases with three, five and seven layers and the maximum calculated error in all cases was less than 12%.
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An original procedure to determine transverse permeability using a multilayer reinforcement in RTM
(2010) Oliveira, Cristiano Peres; Souza, Jeferson Avila; Isoldi, Liércio André; Rocha, Luiz Alberto Oliveira; Amico, Sandro Campos; Silva, Rafael Diego Sonaglio da
Resin Transfer Molding (RTM) is a manufacturing process for polymer composites parts for a variety of uses. The numerical simulation of the resin flow into the mold can be used to minimize costs related to mold design and the manufacturing process itself. However, to obtain realistic results, accurate information about the resin and the reinforcement media are necessary. In the multilayer RTM, distinct porous media layers are stacked to obtain a final composite with better performance. For the numerical simulation of the multilayer RTM, transverse permeability (Kzz) data are necessary. This work proposes an original methodology to determine the transverse permeability in multilayer RTM composites, assuming that the in-plane permeabilities (Kxx and Kyy) are known and using this information, combined with experimental data obtained during mold filling. The motivation of this study is the fact that the transverse permeability is usually not available in the literature, being referred to as a difficult parameter to be directly determined using experiments.
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Application of the computational modeling in the resin transfer molding (RTM) process: a case study of a marine propeller
(2012) Porto, Joseane da Silva; Letzow, Max; Santos, Elizaldo Domingues dos; Souza, Jeferson Avila; Isoldi, Liércio André; Amico, Sandro Campos
This work presents one example of how the computational modeling can help in the Resin Transfer Molding (RTM) process when it is applied to the production of parts with complex geometry, such as the marine propellers. This manufacture process of composite material parts consists in the injection of a polymeric resin into a closed mold where a fibrous reinforcement is previously placed. The numerical simulation of the RTM process can be considered as the resin flow through a porous media. This computational model was developed in the FLUENT package, which is based on the Finite Volume Method (FVM), and was applied to study a propeller for naval propulsion. As the propeller has a complex format, the use of computational approach as a preliminar step in the manufacturing process is very important for the correct definition of the inlet and outlet nozzles. So, it is possible to design an efficient mold, avoinding extras costs related with the mold redesign, the resin waste and the increase of injection time. The results showed that an inadequate positioning of the mold outlet nozzles causes an increase about 10% and 2% in the production time and in the resin amount, respectively, for obtaining the marine propeller by RTM process.
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Avaliação numérica do processo de infusão de resinas em laminados espessos utilizando malha de fluxo
(2019) Dutra, Carla Machado Bulsing; Souza, Jeferson Avila; Amico, Sandro Campos
O presente trabalho é dedicado a estudar numericamente problemas envolvendo o processo de Infusão de Resina Líquida (LRI) em compósitos espessos nos quais um tecido de alta permeabilidade (malha de fluxo) é adicionado na superfície superior da pré-forma para facilitar o escoamento da resina dentro do molde. Nesta técnica, utiliza-se de fibras (naturais ou sintéticas) para a aquisição de compósitos poliméricos que podem ser aplicados em diversos ramos das indústrias e da engenharia. Nesse sentido, há um grande interesse em aprimorar esta técnica para obter um produto final com propriedades físicas e mecânicas que atendam às exigências do mercado atual, além de possibilitar que os custos de fabricação sejam minimizados. Esse estudo tem por objetivo analisar o escoamento da resina dentro do molde e avaliar o comprimento da geometria, a partir do comprimento da malha de fluxo, da relação entre as permeabilidades Kxx/Kzz e da espessura do laminado. Dessa forma, foram investigadas cinco relações de Kxx/Kzz, sendo elas, 0,1, 1, 10, 100 e 1000. Já as espessuras do meio poroso analisadas foram de 0,012 m, 0,0094 m, 0,0069 m, 0,0043 m e 0,0027 m. Para avaliar o comprimento da geometria, o escoamento da resina foi monitorado em dois pontos: próximo as superfícies superior e inferior do molde, e considerou-se que a linha de frente de escoamento estava paralela à saída do molde quando à diferença entre as posições sobre as linhas de monitoramento fosse menor ou igual a 0,00151 m. As simulações numéricas foram realizadas no software livre OpenFOAM e a criação da geometria (2D) e da malha no software GMSH. A formulação de volumes finitos do OpenFOAM foi utilizada para a discretização das equações de transporte que descrevem o escoamento de resina dentro do molde e o tratamento da interface entre os dois fluidos (resina/ar) é resolvido pelo Método Volume of Fluid (VOF). Os resultados e a metodologia proposta para a avaliação da geometria demostraram-se satisfatórias e foi possível obter a posição x(t) na qual formou-se a linha de frente de escoamento paralela à saída do molde em quase todos os casos simulados. Uma análise entre a posição x(t) e o comprimento da malha de fluxo também foi realizada. Por meio dos resultados apresentados, pode-se encontrar uma maneira de generalizar o estudo, e assim, obter o comprimento ideal da malha de fluxo para qualquer comprimento de molde, possibilitando que a linha de frente de escoamento da resina esteja vertical antes do final da pré-forma. Os resultados obtidos proporcionarão facilitar o processo de moldagem experimental por essa técnica, visto que é possível prever o comprimento ideal da malha de fluxo para que a resina preencha o molde em um menor tempo possível.
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Comparação dos métodos VOF e FE/CV aplicados à solução de problemas de RTM
(2011) Oliveira, Cristiano Peres; Souza, Jeferson Avila; Amico, Sandro Campos; Isoldi, Liércio André; Silva, Rafael Diego Sonaglio da
A moldagem por transferência de resina (RTM) é um processo amplamente utilizado na produção de compósitos poliméricos com as mais diferentes geometrias. É um processo de infusão de resina em um molde fechado e preenchido com um reforço fibroso e poroso. Existem algumas variantes do processo de RTM tradicional, como o RTM Light e o VARTM. No estudo desse processo, a simulação numérica desenvolve um papel fundamental, pois através dela pode-se determinar como se dá o avanço da resina no interior do molde e assim perceber possíveis falhas no preenchimento bem como determinar com precisão os pontos mais adequados para a entrada e a saída da resina. Estes fatores possibilitam que haja, por exemplo, uma considerável diminuição do número de ensaios, normalmente de custo elevado, necessários para a construção dos moldes. Para a modelagem numérica do processo RTM são utilizados métodos numéricos para a solução do conjunto de equações diferenciais que governam o problema físico. Nesse trabalho, são apresentados e discutidos os métodos VOF (Volume of Fluid) e FE/CV (Finite Element/Control Volume Method). Para comparação entre os métodos, foram utilizadas as soluções numéricas apresentadas pelo FLUENT® e pelo PAM-RTM®, onde se obteve uma boa concordância entre esses modelos e os resultados experimentais obtidos.
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Computational modeling of RTM and LRTM processes applied to complex geometries
(2012) Porto, Joseane da Silva; Letzow, Max; Santos, Elizaldo Domingues dos; Amico, Sandro Campos; Souza, Jeferson Avila; Isoldi, Liércio André
Light Resin Transfer Molding (LRTM) is a variation of the conventional manufacturing process known as Resin Transfer Molding (RTM). In general terms, these manufacturing processes consist of a closed mould with a preplaced fibrous preform through which a polymeric resin is injected, filling the mold completely, producing parts with complex geometries (in general) and good finish. Those processes differ, among other aspects, in the way that injection occurs. In the RTM process the resin is injected through discrete points whereas in LRTM it is injected into an empty channel (with no porous medium) which surrounds the entire mold perimeter. There are several numerical studies involving the RTM process but LRTM has not been explored enough by the scientific community. Based on that, this work proposes a numerical model developed in the FLUENT package to study the resin flow behavior in the LRTM process. Darcy’s law and Volume of Fluid method (VOF) are used to treat the interaction between air and resin during the flow in the porous medium, i.e. the mold filling problem. Moreover, two three-dimensional geometries were numerically simulated considering the RTM and LRTM processes. It was possible to note the huge differences about resin flow behavior and filling time between these processes to manufacture the same parts.
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Computational modeling of the resin transfer molding process
(2009) Oliveira, Cristiano Peres; Souza, Jeferson Avila; Isoldi, Liércio André; Rocha, Luiz Alberto de Oliveira; Amico, Sandro Campos
The Resin Transfer Molding, or RTM, process has recently become one of the most important processes of fiber reinforced composites manufacturing. The process consists essentially of three stages: “an arrangement of fiber mats in a mold cavity, a mold filling by a polymeric resin and a curing phase”. Most of the difficulties of incorporating RTM occur during the filling stage. To create an acceptable composite part the preform must be completely impregnated with resin. The conditions which most strongly influence the flow are mold geometry, resin rheology, preform permeability, and location of the injection ports and vents. There are different types of RTM process, e.g. RTM Light or VARTM, employed in accordance with the final desired characteristics and properties of composite components. Besides, RTM may also be carried out using multilayers, with distinct characteristics. The numerical simulation of the mold filling stage becomes an important tool which helps the mold designer to understand the process parameters. Considering the fibrous preform as a porous media, the phenomenon can be modeled by Darcy’s law to describe resin flow. This study used two commercial softwares, FLUENT® and PAM-RTM®. FLUENT® is a general Computational Fluid Dynamics (CFD) code, based on Finite Volume Method (FVM). It applies the Volume of Fluid (VOF) method to solve the filling problem because it does not have a specific RTM module. PAM-RTM® is a specific package for RTM problems, based on the Finite Element Method (FEM). These tools were applied to simulate numerically several RTM examples of the resin flow into the mold and the results for both softwares were compared with previous works.
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Constructal design applied to the light resin transfer molding (LRTM) manufacturing process
(2013) Isoldi, Liércio André; Souza, Jeferson Avila; Santos, Elizaldo Domingues dos; Marchesini, Renato; Porto, Joseane da Silva; Letzow, Max; Rocha, Luiz Alberto de Oliveira; Amico, Sandro Campos
The Light Resin Transfer Molding (LRTM) is a manufacturing process where a closed mold pre-loaded with a porous fibrous preform is filled by a liquid resin injected through an empty channel (without porous medium) which runs all around the perimeter of the mold, producing polymeric composite parts. Using the capability of FLUENT® package to simulate a multiphase flow (resin and air) in a geometry composed by porous media regions and empty regions, a computational model based on the Finite Volume Method (FVM) was applied to reproduce the resin flow behavior during the LRTM process. The aim of this work was to define the optimal geometry for the empty channel (border) by means the Constructal Design method. To do so, considering a border with a rectangular cross sectional area, the degree of freedom wb/tb (ratio between the width and thickness of the border) can vary while the border volume is kept constant. The results showed that employing the Constructal Design it is possible to decrease the filling time of the LRTM process in almost 20 %, being this an unpublished use for the Constructal Theory.
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Influence of calcium carbonate on RTM and RTM light processing and properties of molded composites
(2011) Garay, André Cechin; Heck, Vicente; Zattera, Ademir José; Souza, Jeferson Avila; Amico, Sandro Campos
In the RTM light composite manufacturing process, inorganic fillers are commonly added to the resin to reduce cost and alter the final composite properties, especially rigidity, even though they also adversely affect processability. The aim of this study is to evaluate resin characteristics, reinforcement permeability, and mechanical properties of the composite and analyze the detrimental effects when a variable amount of calcium carbonate (CaCO3) is added to the resin. The addition of calcium carbonate increased the viscosity and gel time of the resin and considerably decreased the permeability of the reinforcement and therefore the expected process productivity. Besides, Barcol hardness, short-beam strength, and elastic modulus increased for higher CaCO3 content, whereas Izod impact, flexural, and tensile strengths decreased. Besides, the coarser CaCO3 filler particles managed to penetrate only partially into the fiber-rich layer of the combination mat used, which comprised of a PP flow media core and glass fibers at the surface.
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Numerical analysis of the resin transfer molding process via PAM - RTM Software
(2015) Oliveira, Iran Rodrigues de; Amico, Sandro Campos; Souza, Jeferson Avila; Lima, Antonio Gilson Barbosa de
This work aims to investigate the infiltration of a CaCO3 filled resin in fibrous porous media (resin transfer molding process) using the PAM-RTM software. A preform of glass fiber mat (fraction 30%), with dimensions 320 x 150 x 3.6 mm, has been used in rectilinear injection experiments conducted at room temperature and injection pressure 0.25, 0.50 and 0.75 bar. The polyester resin contain 0% and 40% CaCO3. The numerical results were evaluated by direct comparison with experimental data. The flat flow-front profile of the rectilinear flow was reached approximately half length of the mold. It was observed, that the both velocity infiltration and permeability have decreased with increasing the CaCO3 content, thus, increasing the time to processing of the composite material.
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A numerical investigation of the resin flow front tracking applied to the RTM process
(2011) Souza, Jeferson Avila; Rocha, Luiz Alberto Oliveira; Amico, Sandro Campos; Vargas, Jose Viriato Coelho
Resin Transfer Molding (RTM) is largely used for the manufacturing of high-quality composite components and the key stage during processing is the resin infiltration. The complete understanding of this phenomenon is of utmost importance for efficient mold construction and the fast production of high quality components. This paper investigates the resin flow phenomenon within the mold. A computational application was developed to track the resin flow-front position, which uses a finite volume method to determine the pressure field and a FAN (Flow Analysis Network) technique to track the flow front. The mass conservation problem observed with traditional FE-CV (Finite Element-Control Volume) methods is also investigated and the use of a finite volume method to minimize this inconsistency is proposed. Three proposed case studies are used to validate the methodology by direct comparison with analytical and a commercial software solutions. The results show that the proposed methodology is highly efficient to determine the resin flow front, showing an improvement regarding mass conservation across volumes.
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A numerical methodology for permeability determination of reinforcements for polymeric composites
(2012) Souza, Jeferson Avila; Isoldi, Liércio André; Santos, Elizaldo Domingues dos; Oliveira, Cristiano Peres; Amico, Sandro Campos
This work focus on developing a numerical methodology for the determination of permeability of RTM reinforcements. The method allows the calculation of the three permeability components (Kxx, Kyy and Kzz) from a set of time dependent flow front coordinates data; one coordinate for each permeability component. An initial guess is set for the permeabilities and the difference between numerical and experimental values of flow front position at a specific time is minimized with the solution of an algebraic system of equations. Newton-Raphson method was used to solve the non-linear system of equations. The results presented in this paper were obtained for a rectilinear (1D) and a radial 2D problem, both with analytical solutions for the flow front position as a function of time. For the 1D comparison between the numerically calculated Kxx and the analytical value agreed within 1.7% and, for the 2D radial problem, numerical and analytical values of Kxx and Kyy agreed within 1.3%.
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Numerical simulation of the resin transport through fiber reinforcement medium
(SOUZA, Jeferson Avila; ROCHA, Luiz Alberto Oliveira; AMICO, Sandro Campos. Numerical simulation of the resin transport through fiber reinforcement medium. In: INTERNATIONAL CONGRESS OF MECHANICAL ENGINEERING – COBEM, 19., 2007, Brasília. Anais... Brasília: [s.n.], 2007. Disponível em: . Acesso em: 25 jul. 2015., 2007) Souza, Jeferson Avila; Rocha, Luiz Alberto Oliveira; Amico, Sandro Campos
This paper describes the numerical simulation of the RTM (Resin Transfer Molding) process applied to the modeling of the resin transport through a fibrous reinforcement. The molding volume which is to be impregnated with the resin is considered as a porous medium and the Darcy equation is used to determine the resin transport velocity through the mold. A control volume finite element method is used for the determination of the pressure gradients inside the mold and the resin flow front advance is obtained using a FAN technique. The finite volume method was built to be used with a bi-dimensional unstructured grid, hence allowing the discretization of complex geometries. In the simulation presented here, resin physical properties, like viscosity and density, and the permeability of the media were kept constants.
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Resin transfer molding process: a numerical analysis
(2014) Oliveira, Iran Rodrigues de; Amico, Sandro Campos; Souza, Jeferson Avila; Lima, Antonio Gilson Barbosa de
This work aims to investigate the infiltration of a CaCO3 filled resin using experiments and the PAM-RTM software. A preform of glass fiber mat, with dimensions 320 x 150 x 3.6 mm, has been used for experiments conducted at room temperature, with injection pressure of 0.25bar. The resin contained 10 and 40% CaCO3 content with particle size 38μm. The numerical results were evaluated by direct comparison with experimental data. The flat flow-front profile of the rectilinear flow was reached approximately halfway the length of the mold. It was observed, that the speed of the filling decreases with increasing CaCO3 content and,the higher the amount of CaCO3 in the resin, the lower the permeability of the reinforcement that is found. The reduction in permeability is due to the presence of calcium carbonate particles between the fibers, hindering the resin flow in the fibrous media. The computational fluid flow analysis with the PAM-RTM proved to be an accurate tool study for the processing of composite materials.
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Resin transfer molding process: a numerical and experimental investigation
(2013) Oliveira, Iran Rodrigues de; Amico, Sandro Campos; Souza, Jeferson Avila; Lima, Antonio Gilson Barbosa de
Resin Transfer Molding (RTM) is one of the composite manufacturing technique that consists in injecting a resin pre-catalysed thermosetting in a closed mold containing a dry fiber preform, where the resin is impregnated. In this sense, the aim of this research is to study theoretically and experimentally the RTM process. Experimental and simulations of the rectilinear infiltration of polyester resin (filled and non filled with CaCO3) in mold with glass fiber preform were performed in cavity with dimensions 320 × 150 × 3.6 mm. Numerical results of the filling time and fluid front position over time were assessed by comparison with experimental data and good accuracy was obtained. It was verified that, the CaCO3 content affect resin velocity during filling, the permeability of the reinforcement and resin viscosity, thus the filling time is affected strongly.
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Resin transfer molding process: a numerical investigation
(Trans Tech Publications, 2013) Oliveira, Iran Rodrigues de; Amico, Sandro Campos; Souza, Jeferson Avila; Luz, Felipe Ferreira; Barcella, Rodrigo Araujo; Lima, Antonio Gilson Barbosa de
In the processing of high performance composite materials, the RTM process has been widely used by many sectors of the industry. This process consists in injecting a polymeric resin through a fibrous reinforcement arranged within a mold. In this sense, this study aims to simulate the rectilinear infiltration of pure resin and filled resin (40% CaCO3) in a mold with glass fiber preform, using the PAM-RTM commercial software. Numerical results of the filling time and fluid front flow position over time were assessed by comparison with the experimental data and a good accuracy was obtained.
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Studies on thermal and viscoelastic properties of vinyl ester resin and its composites with glass fiber
(2015) Garay, André Cechin; Paese, Lucas Tosin; Souza, Jeferson Avila; Amico, Sandro Campos
Vinyl ester resins are widely used in sandwich composite structures. Because of their good resistance to chemicals, flexibility and easy processing, these sandwich are extensively applied in the marine sector. These composites are typically manufactured by liquid molding processes, especially infusion. In this study, RTM light was used to inject the polymeric resin into the mold cavity, flowing in the space between the impermeable core and the mold walls, where the fibrous medium was. In this process, viscosity, gel time and curing time of the resin are very important parameters. This work addressed the curing and post-curing characteristics of a vinyl ester resin, and also the characteristics of neat and reinforced vinyl ester using dynamic mechanical analysis (DMA). The increase in shear rate did not significantly influence resin viscosity within the studied range. Differential scanning calorimetry showed the efficiency of the post-curing stage, with the decrease in residual enthalpy. With DMA, it was possible to determine gel time and gel temperature, which yielded similar values to those found by the SPI (Society of the Plastics Industry) method, indicating that the simpler SPI method can be reliably used for that.
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Three-dimensional numerical modeling of RTM and LRTM processes
(2012) Isoldi, Liércio André; Oliveira, Cristiano Peres; Rocha, Luiz Alberto Oliveira; Souza, Jeferson Avila; Amico, Sandro Campos
Resin Transfer Molding (RTM) is a manufacturing process in which a liquid resin is injected into a closed mold pre-loaded with a porous fibrous preform, producing complex composite parts with good surface finishing. Resin flow is a critical step in the process. In this work, the numerical study of the resin flow in RTM applications was performed employing a general Computational Fluid Dynamics software which does not have a specific RTM module, making it necessary to use the Volume of Fluid method for the filling problem solution. Examples were presented and compared with analytical, experimental and numerical results showing the validity and effectiveness of the present study, with maximum difference among these solutions of around 8%. Besides, based on the computational model for the RTM process, a new computational methodology was developed to simulate Light Resin Transfer Molding (LRTM). In this process, resin is injected into the mold through an empty injection channel (without porous medium) which runs all around the perimeter of the mold. The ability of FLUENT® package to simulate geometries which combine porous media regions with open (empty) regions was used. Two specific cases were simulated, showing the differences in time and behavior between RTM and LRTM processes.
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Two-dimensional Control Volume Modeling of the Resin Transfer in a Porous Media with a Heterogeneous Permeability Tensor
(2008) Souza, Jeferson Avila; Nava, Marcelo José Anghinoni; Rocha, Luiz Alberto Oliveira; Amico, Sandro Campos
Resin Transfer Molding (RTM) is a polymer composite processing technique widely used in the aeronautics and automotive sectors. This paper describes the numerical simulation of the RTM process where Darcy’s law was used for the mathematical formulation of the problem. A control volume finite element method was used for the determination of pressure gradients inside the mold, and a geometric reconstruction algorithm is used for the resin flow-front determination. Permeability of the medium was considered either a constant or a two dimensional tensor. The application was validated by direct comparison with literature data and good qualitative and quantitative agreement was obtained. The finite volume method was built to be used with a two-dimensional unstructured grid, hence allowing the analysis of complex geometries. The results showed that the proposed methodology is fully capable of predicting resin flow advancement in a multi-layer (with distinct physical properties) reinforced media.