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Projeto de investigação
Strategic Project - UI 285 - 2013-2014
Financiador
Autores
Publicações
Effect of friction stir processing parameters on the microstructural and electrical properties of copper
Publication . Leal, Rui; Galvão, I.; Loureiro, A.; Rodrigues, D. M.
Friction stir processing (FSP) is an innovative technology, based on friction stir welding (FSW) operative principles, which can be used for changing locally the microstructure and the mechanical properties of conventional materials. In this work, the copper alloy C12200 was friction stir processed using two distinct tools, i.e. a scrolled and a conical shoulder tool, in order to promote different thermomechanical conditions inside the stirred volume, and consequently, varied post-processed microstructures. The influence of the tool geometry and tool rotation and traverse speeds on the microstructural and electrical properties of the processed copper alloy was analysed. The processing conditions were found to have an important influence on the electrical conductivity of the processed material. The differences in electrical conductivity were explained based on dislocations density effects. The effect of the dislocations density on electrical conductivity of the processed material was found to prevail over the effect of the grain boundaries.
Mechanical behavior of high dosage short carbon fiber reinforced epoxy composites
Publication . Capela, C.; Oliveira, S. E.; Ferreira, J. A. M.
Short fibers are effective reinforcements in strengthening and toughening polymer materials, even small amounts of fibers. However, for high fiber dosage the achieved dispersion and interface adhesion is quite poor reaching to lower stiffness and strength efficiency. In high dosage composites, the effects of the fiber length and volume fraction on mechanical properties is not entirely consensual; nonetheless this paper intends to contibute for a better understanding of this occurrence.
Composite plates were manufactured by compression moulding, using short carbon fibers reinforcements (2, 4 and 6 mm in length) with 45-75 % wt fiber fraction. Tensile and dynamic mechanical analysis (DMA) specimens were machined from
molded plates for the desired dimensions. DMA was performed with bi-supported specimens in temperature ranged from 20 to 180 oC. High dosage composites exhibit very low efficiency parameters both in stiffness and particularly in tensile strength. However, the stiffness increases in order of 25 % when fiber length increases from 2 mm to 4 mm, but afterwards tends to decrease for 6 mm fiber length composites. The same tendency was observed for the tensile strength. For very high fiber dosage composites, tensile strength decreases and Young’s modulus tends to remain at constant values. However, the results of DMA indicate that bending modulus storage increases when fiber length increases from 2 mm to 6 mm.
Self Similarity of Sousa Ramos’s Trees and Mira’s Boxes Within the Boxes
Publication . Baptista, Diogo; Fournier-Prunaret, Daniele; Grácio, Clara; Fernandes, Sara
This work consists on the theory of embedded boxes structure [7], from the point of view of the theory of symbolic dynamics [6], tree structure Ramos [8], [9], [10] and star product [1] . This merger allowed the outcome-applications defined on the real line and a better understanding of the structure of the bifurcation, which allows us to characterize and understand the dynamics behind an application within the chaotic dynamical systems.
Effect of machining parameters on the mechanical properties of high dosage short –carbon- fiber reinforced composites
Publication . Ferreira, José; Oliveira, Sergio; Silva, Joel; Capela, Carlos
The machinability of polymer matrix composites with fibers strongly depends on the type of fiber and dosage in question, having a high influence on the selection of tools and cutting parameters. The cutting temperature depends of rotation speed and the feed cutting tools and is significantly influencing on the quality of the machined surfaces and tool life. This paper presents the results of a current study concerning the effect of the rotation-cutting speed on the cutting temperature, roughness and tensile strength of short carbon fiber reinforced epoxy composites, potentially used in automotive and aeronautic industries. Composite plates were manufactured by compression molding, using short carbon fibers with 0.5 mm and 6 mm length. The increasing of the rotation-cutting speed increases significantly the temperature generated in the tool and slightly increases surface roughness. Tensile strength and Young´s modulus are little sensitive to drilling speed. However, above 3000 rpm it was observed significant loss of stiffness, associated with the developed temperature in the machining process. Citation: Oliveira, S. E., Ferreira, J.A.M., Capela, C., da Silva, J., Effect of machining parameters on the mechanical properties of high dosage short-carbon-fiber reinforced composites, Frattura ed Integrità Strutturale, 48 (2019) 249-256.
Binder system for fused deposition of metals
Publication . Cruz, N.; Santos, L.; Vasco, Joel; Barreiros, F. M.
Fused Deposition of Metals (FDMe) is a technique developed to produce metallic components, based on the extrusion of metal/binder filaments to form layer by layer three dimensional objects. Filament materials must contain a high content of metallic powder to prevent shrinkage on thermal treatments like debinding and sintering, without compromising adequate rheological properties during the extrusion process. This research aims developing an FDMe system using metal/binder feedstocks in pellet/granule instead of filaments. The present work is focused on establishing a suitable binder system for fused deposition of carbonyl iron feedstocks. Binder systems based on Polyethylene Wax (PEW) or Paraffin Wax (PW), Polyethylene Glycol (PEG) and Polypropylene (PP) were investigated concerning their thermal and rheological properties. The rheological data showed that the binder systems containing PW presents lower viscosity than those having PEW. Thus, a binder system based on the former component was selected to assure appropriate rheological properties of carbonyl iron feedstocks with high content of solids for FDMe.
Unidades organizacionais
Descrição
Palavras-chave
Mechanical Technology and Structural Integrity,Nanomaterials Micromanufacturing & Surface Eng.,Sensors and Nano-electochemistry,Smart Industrial Robotics and Management, Engineering and technology ,Engineering and technology/Electrical engineering, electronic engineering, information engineering
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia, I.P.
Fundação para a Ciência e a Tecnologia, I.P.
Fundação para a Ciência e a Tecnologia, I.P.
Programa de financiamento
6820 - DCRRNI ID
Concurso para Financiamento de Projectos de IC&DT Estratégicos e de Interesse Público promovidos por Laboratórios Associados e Unidades de I&D - 2013 - COMPETE
Concurso para Financiamento de Projectos de IC&DT Estratégicos e de Interesse Público promovidos por Laboratórios Associados e Unidades de I&D - 2013 - COMPETE
Número da atribuição
PEst-C/EME/UI0285/2013