Bruno Ramoa

Mr. Bruno Ramoa


Research Focus & Metrics

Academic Career Length

7Years (2020-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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29 May 2020 in Fluids
Verified
Journal Article
Open access
PDF file
JPJoão Pedro
João Pedro
BRBruno Ramoa
Bruno Ramoa
JNJoão Nóbrega
João Nóbrega
CFCélio Fernandes
Célio Fernandes
In the present study, the simulation of the three-dimensional (3D) non-isothermal, non-Newtonian fluid flow of polymer melts is investigated. In particular, the filling stage of thermoplastic injection molding is numerically studied with a solver implemented in the open-source computational library O p e n F O A M ® . The numerical method is based on a compressible two-phase flow model, developed following a cell-centered unstructured finite volume discretization scheme, combined with a volume-of-fluid (VOF) technique for the interface capturing. Additionally, the Cross-WLF (Williams–Landel–Ferry) model is used to characterize the rheological behavior of the polymer melts, and the modified Tait equation is used as the equation of state. To verify the numerical implementation, the code predictions are first compared with analytical solutions, for a Newtonian fluid flowing through a cylindrical channel. Subsequently, the melt filling process of a non-Newtonian fluid (Cross-WLF) in a rectangular cavity with a cylindrical insert and in a tensile test specimen are studied. The predicted melt flow front interface and fields (pressure, velocity, and temperature) contours are found to be in good agreement with the reference solutions, obtained with the proprietary software M o l d e x 3 D ® . Additionally, the computational effort, measured by the elapsed wall-time of the simulations, is analyzed for both the open-source and proprietary software, and both are found to be similar for the same level of accuracy, when the parallelization capabilities of O p e n F O A M ® are employed.

2 April 2023 in Polymers
Verified
Journal Article
Open access
PDF file
Pedro Veiga RodriguesPedro Veiga Rodrigues
Pedro Veiga Rodrigues
BRBruno Ramoa
Bruno Ramoa
ATAna Rita Torres
Ana Rita Torres
CCCidália Castro
Cidália Castro
AMAna Machado
Ana Machado
A systematic study was performed to provide better understanding of the effect of elastomeric materials on the behavior of polycarbonate blends (PC). Thus, blends of PC with different amounts of elastomers, such as copolyether ester elastomer (COPE), acrylonitrile–butadiene–styrene (ABS), maleic anhydride-grafted ABS (ABS-g-MA), and styrene–ethylene–butylene–styrene (SEBS-g-MA) were prepared in a co-rotating twin-screw extruder. The materials were characterized by an electronic microscopy (SEM), an infrared spectroscopy (FTIR), and thermal (DSC) and thermo-mechanical (DMA) techniques. The incorporation of elastomeric phases was observed by changes in the FTIR band’s intensity, whereas a new shoulder of the ester band of COPE at 1728 cm−1 indicates the occurrence of a transesterification reaction. Unmodified and modified ABS (5% and 10%) did not affect the glass transition temperature (Tg) of PC, while 1% SEBS-g-MA slightly increased this value. PC/10% COPE showed that a decrease in Tg of 25 °C has a result of better compatibilization between both phases, which is visible via SEM. SEM analysis identified three main toughening mechanisms, depending on the type of elastomer. Unlike any other study, this work deepens the knowledge, in a comparative way, to understand the elastomeric effect at the interface and consequently, on the mechanical behavior of PC systems.

10 December 2021 in Polymers
Verified
Journal Article
Open access
PDF file
Pedro Veiga RodriguesPedro Veiga Rodrigues
Pedro Veiga Rodrigues
BRBruno Ramoa
Bruno Ramoa
AMAna Machado
Ana Machado
PCPhilip Cardiff
Philip Cardiff
JNJoão Nóbrega
João Nóbrega
Toe caps are one of the most important components in safety footwear, but have a significant contribution to the weight of the shoe. Efforts have been made to replace steel toe caps by polymeric ones, since they are lighter, insulated and insensitive to magnetic fields. Nevertheless, polymeric solutions require larger volumes, which has a negative impact on the shoe’s aesthetics. Therefore, safety footwear manufacturers are pursuing the development of an easy, low-cost and reliable solution to optimize this component. In this work, a solid mechanics toolbox built in the open-source computational library, OpenFOAM®, was used to simulate two laboratory standard tests (15 kN compression and 200 J impact tests). To model the polymeric material behavior, a neo-Hookean hyper-elasto-plastic material law with J2 plastic criteria was employed. A commercially available plastic toe cap was characterized, and the collected data was used for assessment purposes. Close agreements, between experimental and simulated values, were achieved for both tests, with an approximate error of 5.4% and 6.8% for the displacement value in compression and impact test simulations, respectively. The results clearly demonstrate that the employed open-source finite volume computational models offer reliable results and can support the design of toe caps for the R&D footwear industry.

15 August 2024 in Polymers
Verified
Journal Article
Open access
PDF file
Pedro Veiga RodriguesPedro Veiga Rodrigues
Pedro Veiga Rodrigues
BRBruno Ramoa
Bruno Ramoa
CCCidália Castro
Cidália Castro
AMAna Machado
Ana Machado
Despite polycarbonate (PC) being a widely used engineering plastic, its notch and crack sensitivity pose challenges in critical applications. To address this, PC was blended with elastomeric polymers to explore the improvement in toughness. This study systematically investigates the toughening mechanisms of PC blended with acrylonitrile–butadiene–styrene (ABS), copolyether ester elastomer (COPE), and ABS and styrene–ethylene–butylene–styrene (SEBS) copolymer grafted with maleic anhydride (MA). The morphology and mechanical behavior were evaluated under quasi-static and medium-strain-rate tensile tests and Charpy impact tests using optical, electronic, and atomic force microscopy and Raman mapping spectroscopy. The morphological analysis reveals cavitation and crazing phenomena for COPE and SEBS-g-MA systems, and mostly debonding for ABS, indicating an improvement in toughening. While the addition of ABS improves the PC plastic deformation, modifying ABS with maleic anhydride enhances the elastic modulus. Blending PC with SEBS-g-MA increases the strain at break, and the addition of COPE significantly improves the deformation behavior of PC (by around 115%). This comparative study provides valuable insights into the performance of different PC–elastomer blends under similar conditions, supporting the selection of appropriate materials for given applications.

6 June 2024 in Preprints.org
Verified
Preprint
Open access
PDF file
Pedro Veiga RodriguesPedro Veiga Rodrigues
Pedro Veiga Rodrigues
BRBruno Ramoa
Bruno Ramoa
CCCidália Castro
Cidália Castro
AMAna Machado
Ana Machado
Despite polycarbonate (PC) being a widely used engineering plastic, its notch and crack sensitivity pose challenges in critical applications. To address this, PC was blended with elastomeric polymers to explore the improvement in toughness. This study systematically investigates the toughening mechanisms of PC blended with acrylonitrile-butadiene-styrene (ABS), copolyether ester elas-tomer (COPE), and ABS and styrene-ethylene-butylene-styrene (SEBS) copolymer grafted with maleic anhydride (MA). The morphology and mechanical behavior were evaluated under qua-si-static and high-speed tensile tests and Charpy impact tests using optical, electronic, and atomic force microscopy and Raman spectroscopy. The morphological analysis reveals cavitation and crazing phenomena for COPE and SEBS-g-MA systems, and mostly debonding for ABS, indicating an improvement in toughening. While the addition of ABS improves the PC plastic deformation, modifying ABS with maleic anhydride enhances the elastic modulus. Blending PC with SEBS-g-MA increases the strain at break, and the addition of COPE significantly improves the deformation behavior of PC (by around 115%). This comparative study provides valuable insights into the performance of different PC-elastomer blends under similar conditions, supporting the selection of appropriate materials for given applications.

16 November 2022 in OpenFOAM® Journal
Verified
Journal Article
Open access
PDF file
BRBruno Ramoa
Bruno Ramoa
RCRicardo Costa
Ricardo Costa
FCFrancisco Chinesta
Francisco Chinesta
JNJoão Nóbrega
João Nóbrega
Code verification is an intricate and crucial part of code developed. Due to the nature of the partial differential equations being solved, an analytical solution might not exit. To prove that the code is solving the correct equations, the method of manufactured solutions (MMS) is the go to approach. In this method we create a forcing term to drive the solution to a predetermined function. By performing a mesh refinement study, we can verify if the code is solving correctly the governing equations. In this work, we present the procedure of MMS as well as a tool developed in an open-source software for symbolic computation of the forcing term, appropriate boundary conditions and error norm computation withing the OpenFOAM® framework.