Percorrer por autor "Carreira, P."
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- An Additive Manufacturing Solution to Produce Big Green Parts from Tires and Recycled PlasticsPublication . Domingues, J.; Marques, T.; Mateus, A.; Carreira, P.; Malça, C.Recycling is crucial for the conservation and improvement of the environment. The reduction of natural resource exploration and recovery of waste are examples of actions to contribute to a sustainable development. Waste from end-of-life tires and undifferentiated plastics represents an environmental problem due to the very high number of tons of used tires and plastics produced, but with a high economic potential because their incorporation into high value-added products is an issue of utmost importance. The manufacturing technologies oriented to the increase in quality levels, functional advantages, structural and financial gains of the produced products are currently a hot topic in industry. Similarly, the use of additive manufacturing technologies, instead of conventional techniques, e.g. moulding to process materials obtained from waste recovery, is a great industrial challenge. In order to promote greater environmental responsibility and to present innovative solutions for the management and sustainable destination of used waste recovery from tires and undifferentiated plastics, a composite made from the blend of 60% of tire waste granulate and 40% of polypropylene (PP) recycled was tested with the final purpose of generating components with added value. Both waste recovery materials were used in the micronized state. The thermal and mechanical behaviours of the synthesized composite were studied through DSC/TGA analysis and tensile testing. The implementation of additive manufacturing methodologies to process the blends between used tires granulated with a high incorporation of wastes from undifferentiated plastics was also explored in this work in order to produce big green parts without mould needed, such as urban furniture.
- A Computer Simulation of the Nitinol Thermal Expansion under Fast Varying Working ConditionsPublication . Ferreira, P. Castelo; Pascoal-Faria, P.; Carreira, P.; Alves, N.We discuss the setup of a simulation on ANSYS to predict the thermal expansion of parts made of Nitinol. A simulation is justified for working conditions in which the part heating is not ho-mogeneous originating a temperature gradient across the part section such that an analytical estimate for the part expansion cannot be calculated. We apply the simulation to the topological optimization of a square section geometry and a bullet geometry for water assisted injection molding. For the topo-logical optimization we consider as parameter the wall thickness and consider both the cases of fast varying temperature and fast varying temperature and pressure.
- A Novel Biomanufacturing System to Produce Multi-Material Scaffolds for Tissue Engineering: Concept and Preliminary ResultsPublication . Viana, T.; Biscaia, S.; Dabrowska, E.; Franco, M.; Carreira, P.; Morouço, P.; Alves, N.This research work aims to validate a new system that enables the fabrication of multimaterial 3D structures using poly(e-caprolactone) and sodium alginate for potential use in Tissue Engineering applications. To produce multi-material scaffolds for Tissue Engineering, accurate techniques are needed to obtain three-dimensional constructs with clinically appropriate size and structural integrity. This paper presents a novel biomanufacturing system which can fabricate 3D scaffolds with precise shape and porosity, through the control of all fabrication modules by an integrated computational platform. The incorporation of a clean flow unit and a camera makes it possible to produce scaffolds in a clean environment and provides a monitoring tool to analyse constructs during the production, respectively.
- Numerical study on injection parameters optimization of thin wall and biodegradable polymers partsPublication . Santos, Cyril; Mendes, A; Carreira, P.; Mateus, Artur; Malça, C.Nowadays, the molds industry searches new markets, with diversified and added value products. The concept associated to the production of thin walled and biodegradable parts mostly manufactured by injection process has assumed a relevant importance due to environmental and economic factors. The growth of a global consciousness about the harmful effects of the conventional polymers in our life quality associated with the legislation imposed, become key factors for the choice of a particular product by the consumer. The target of this work is to provide an integrated solution for the injection of parts with thin walls and manufactured using biodegradable materials. This integrated solution includes the design and manufacture processes of the mold as well as to find the optimum values for the injection parameters in order to become the process effective and competitive. For this, the Moldflow software was used. It was demonstrated that this computational tool provides an effective responsiveness and it can constitute an important tool in supporting the injection molding of thin-walled and biodegradable parts.
- Produção de peças biodegradáveis de parede fina por injeçãoPublication . Santos, C.; Mendes, A.; Carreira, P.; Mateus, A.; Alves, N.Actualmente, a indústria dos moldes para responder às exigências do mercado procura diversificar os seus mercados, apostando em produtos diferenciados e de valor acrescentado. Foi neste sentido que se desenvolveu o projecto de concepção e fabrico de vasos biodegradáveis para germinação de plantas. O objectivo deste artigo de investigação passa pela concepção e desenvolvimento de um vaso para germinação de plantas produzido em material biodegradável. A validação do projecto desenvolvido para uma peça de paredes finas em material biodegradável, foi realizada através da fabricação da ferramenta (molde) e o processamento de peças (vasos biodegradáveis). Este estudo demonstrou-se promissor como pilar de apoio para o desenvolvimento de futuros produtos em materiais biodegradáveis de paredes finas, obtidos pelo processo de injecção de termoplásticos. Os resultados alcançados permitiram validar o processo desenvolvido, bem como o produto obtido de paredes finas em material biodegradável, que neste caso foi um vaso biodegradável para germinação de plantas.
- Water Assisted Injection Molding for Single and Multi-branched Tubular ComponentsPublication . Oliveira, D.; Mateus, A.; Carreira, P.; Simões, F.; Malça, C.To produce hollow polymeric parts with complex geometries the Fluid Assisted Injection (FAI) technology is currently used. In this technology water and gas can be employed with or without the aid of a projectile. The process consists in the injection of water at high pressures, after the closing of the mold and polymer injection, and up to the filling of the whole molding zone. The injection of water at high pressures will force the polymer from the core to be expelled to a reservoir. This material expulsion is possible, not only thanks to the high water pressures, but also because the polymer is still in a viscous state, thus facilitating the evacuation. Even though the FAI technology is by direct injection of water/gas or with aid of a projectile, there is a common limitation, which is the inability to produce hollowed parts with forking channels. However, even if creating these branches is possible, there is the impossibility of them being geometrically complex and/or extensive. In these cases, the branches are created with inserts inside the mold, meaning that they will always be limited by a molding insert, and not controlled by the water jet. For cases where it is desired to add complex and/or extensive ramifications, subsequent steps of production and assembling must be added, influencing the overall production time. This work aims, therefore, at studying a new approach for the production of hollow parts with extensive branched channels and complex geometries within a single injection cycle, and thus eliminating subsequent processes that are currently required. The first approach is the application of several water injectors, guided towards the respective branches where hollow sections are intended to be produced. This innovation will have an impact on the serial production of high complexity tubular type parts, reducing the production time with the elimination of subsequent processes. Furthermore, a saving of raw materials is achieved by eliminating the necessity of a creation of additional molds. In this work, a detailed experimental study of the water assisted injection process was done to serve as a knowledge base to the concept of the new process named Multi-Path.H2O.