Browsing by Author "Marat-Mendes, R."
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- Assessment of Replacement of Metal Parts by BFRP Composites into a Highly Efficient Electrical PrototypePublication . Marat-Mendes, R.; Ribeira, D.; Reis, L.This work intends to evaluate the use of epoxy composite materials reinforced with basalt fibers as replacement to metallic mechanical parts of a highly efficient electrical prototype. The analysis of the behavior of the original metallic bracket was made and an optimization process was carried out in order to achieve the most suitable geometry and stacking sequence if produced in composite material. Finite element analysis using Siemens NX12 and experimental tests to the produced composite part were performed in order to access it. It was verified that the total weight of the composite part shows a 45% reduction. The composite part shows a higher deformation than the metallic one due to basalt fiber’s higher flexibility. However, the advantages added by the new component largely compensate for the disadvantages that may have been added without compromising its performance. Obtained results show that the use of basalt fiber reinforced composites as the material of mechanical parts of a highly efficient electrical prototype that is a good alternative.
- Effect of Fused Filament Fabrication Processing Parameters on The Mechanical Properties of PLA ComponentsPublication . Marat-Mendes, R.; Guedes, M.; Leite, M.; Baptista, R.This paper studies the influence of Fused Filament Fabrication processing parameters upon mechanical properties and microstructural features of processed PLA parts. The effect of extrusion temperature and raster angle were tested upon two PLA filaments of different trademarks, DoWire and BQ, using a commercial fused deposition extruder. The filling density, layer thickness and velocity were kept constant at 60 %, 0.2 mm and 40 mm/s, respectively. Results allowed to determine fused filament fabrication parameters resulting in increased mechanical performance of manufactured parts. Mechanical performance is higher when material is stored under controlled atmosphere before use, and when material deposition direction is aligned with applied load. Increasing the extrusion temperature also increases performance, by increasing deformation ability of PLA molecules. Obtained results contribute to accumulation of a property database and provide design guidance to the procurement of additive manufacturing products with enhanced mechanical strength.
- Evaluation of tribological performance of carbon fibre reinforced epoxy composites loaded with graphite platelets under reciprocating linear motion. Proceedings of the Institution of Mechanical Engineers, Part JPublication . Marat-Mendes, R.; Rodrigues, I.; Figueiredo-Pina, C.G.The objective of this work was to evaluate the effect of graphite platelets used as matrix epoxy polymer reinforcement in the sliding zeciprocating wear performance of carbon fibre composites. First, epoxy reinforced composites with different amounts of graphite in weight were produced (0, 7.5, 11.5 and 30 wt %) to ascertain the optimal composition regarding wear resistance. Additionally, carbon fibre reinforced polymer composites were produced, with and without the addition of 7.5 wt% graphite platelets to the polymer matrix, and its wear resistance was also evaluated. The laminated carbon fibre reinforced polymer composites were produced through vacuum assisted hand lay-up method. Reciprocating sphere-on-plate wear tests, using Ø 6mm spheres of AISI52100 steel as counter-body, were performed during 6 h at room temperature. The tests were carried out using an applied normal load of 4 N, 2 Hz of frequency and 8mm stroke per cycle. At the end of the tests, the wear losses were estimated through integration of cross-section wear track profiles and the worn surfaces were examined by scanning electron microscopy. The coefficient of friction was accessed during testing. The results showed that the lowest specific wear rate of the polymer composites without carbon fibre was obtained with the insertion of 7.5 wt% of graphite platelets and that increase in the graphite fraction leads to higher material loss as a result of increased fatigue surface. Furthermore, the addition of 7.5 wt% graphite platelets to the epoxy matrix of carbon fibre reinforced polymer composites leads to enhance its wear resistance. The reinforced matrix supports and protects the fibres reducing fibre failure and, consequently, wear.
- Experimental and Numerical Characterization of Stress-Strain Fields on Sandwich Beams, Subjected to 3PB and 4PBPublication . Marat-Mendes, R.; Martins, R.; Reis, L.
- Extended- Range Marine Unmanned Surface Vehicles for Border Surveillance MissionsPublication . Fernandes, J. F. P.; Branco, P. J. Costa; Marat-Mendes, R.; Póvoa, R.; Teodoro, P.; Neves, J.; Marques, H.; Pinheiro, P.; Afonso, P.; Serrano, D.; Assunção, M.This work focuses on the development of extended-range marine unmanned surface vehicles (USV) for border surveillance missions. USVs present many advantages for marine applications due to their energy-saving capabilities and lack of in-board pilot needs. Nevertheless, due to their small scales, USVs often present reduced mission ranges. In order to overcome this handicap, this work proposes the application of innovative energy management strategies to optimize the available energy during one mission. This solution is based on path and speed optimizations, taking into account the most probable weather and sea conditions, to define a mission plan. The proposed energy management optimization is supported by the USV simulation model. This model is calibrated and verified with two experimental tests: one in an indoor swimming pool and the other in an outdoor enclosed harbour. Applying the proposed optimization strategy results in energy savings between 10 and 35.9%, subject to the maximization of mission time. This work is carried out within the international project SEMS4USV, supported by Frontex.
- Flexural testing and analysis of fullstrain-fields in sandwich composites.Publication . Marat-Mendes, R.; Martins, R.; Garcia, A.; Reis, L.The objective of this work was to characterize the full-field flexural behavior of composite sandwich beams. Finite element analysis was used to estimate the behavior of sandwich beams under three- and four-point-bending tests and were compared with experimental results obtained via digital image correlation and strain-gauges. Two different polyurethane core thicknesses and two different sandwich lengths were used to simulate short- and long-beam. Two distinct sandwich beams were used by means of two different faces: aluminum and basalt fiber reinforced polymer composite. Full-strain-fields and flexural displacements results were obtained showing that BFRP sandwiches exhibited higher flexibility and higher capacity of absorption energy than the aluminum specimens however with a higher prospect of core shear failure. For both face materials short-beams present higher strains than the long-beams and 4PB test specimens showed negative strain distribution in the upper side of the specimen and positive in the underside contrary to 3PB that presents positive strain distribution along the fulfilled. Moreover, results show that the strain distribution in not symmetric. Obtained experimental results are in good agreement with estimations; the digital image technique attested to be a complementary method to strain gages measurements in experimental full-strain-fields analysis.
- Instigating Maritime Studies via Rapid Prototyping and Robotics: A Case From the Smartboat InitiativePublication . Teodoro, Pedro; Marat-Mendes, R.; Assunção, Mário; Alves, Nuno; Sanguino, Beatriz; Gaspar, Henrique M.A case on rapid prototyping is presented in this work to exemplify the use of learn, make and share activities to promote maritime studies. SMARTBOAT is an initiative from the Escola Superior Náutica Infante D. Henrique, in Portugal, where students are invited to interact with computer-aided design modelling, additive manufacturing and programming. Such initiative is paramount to instigate and promote higher education studies in science, technology, engineering, art, and mathematics (STEAM). The initiative is presented and discussed, with its main steps and schemes. A step forward is later discussed by the ongoing collaboration with the Norwegian University of Science and Technology (NTNU, Norway), which intend to combine the Portuguese case with recent advancements in robotics and digital twin, such as remote operation via internet of things protocols and web-based tools. The work ends with a discussion on the results and future works on autonomous shipping, as well as a call for the development and sharing of similar initiatives.