Strategic Project - UI 285 - 2013-2014

Publications

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.

2015-04Journal article

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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.

2017-06Journal article

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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.

2015-09Journal article

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Keywords

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

Funding agency

Fundação para a Ciência e a Tecnologia, I.P.
Fundação para a Ciência e a Tecnologia, I.P.

Funding programme

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

Funding Award Number

PEst-C/EME/UI0285/2013