Authors: D. Janković Ilić, J. Fiscina, C.J.R. González-Oliver, F. Mücklich
Abstract: The Cu/W functionally graded material (FGM) was produced by vibration of W
agglomerates in order to obtain the W skeleton with a gradient in porosity, which after pressureless sintering was infiltrated with molten Cu. Certain sintering mechanisms are suggested for these complex W structures. The segregation of two different sizes of W agglomerates was controlled by vibration time. Different vibration duration resulted in different types of microstructure: skeleton type microstructure after shorter vibration time and graded type microstructure after extended vibration times. The final Cu-infiltrated FGMs were characterized microstructurally and their
electrical resistivity (r) was measured using the 4-probe technique. The values of r were in between those for pure W and Cu, depending strongly on the vibration times of the initial W agglomerates, and exhibiting particular r vs. T (K) behavior.
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Authors: M. Carmo Lança, Stefan Peuckert, Eugen R. Neagu, Luís Gil, Paulo C. Silva, José N. Marat-Mendes
Abstract: Lately the electrical and dielectric properties of cork and some cork-based materials
(commercial and non-commercial) have been studied in order to understand their ability to store
electrical charge. The main problem found so far is related to the water content in cork, only of a
few % weight, but large enough to influence greatly the conductivity of cork and, consequently, the
charge storage capability. To overcome this problem cork has been combined with hydrophobic
materials. In this work a commercial wax (paraffin wax) was used to produce a cork/paraffin
composite by hot pressing. After milled and mixed natural cork, TetraPak® containers waste and
paraffin were pressed to make plaques of a new composite. Different concentrations of cork,
TetraPak® and paraffin, different granules size, different temperature and pressure were used to
produce the samples. The electrical properties of the new composite were measured by the
isothermal charging and discharging current method and the results compared to previously ones
obtained for natural cork and other derivative products. The new composite has shown to have
lower conductivity than the commercial agglomerate, which makes it a better material for charge
storage.
613
Authors: José M. Silva, Tessaleno C. Devezas, A. Silva, L. Gil, C. Nunes, N. Franco
Abstract: Aerospace components are characterized by having high strength to weight ratios in order to obtain lightweight structures. Recently, different types of sandwich components using composite materials have been developed with the purpose of combining the effect of reinforced face-sheets with low weight core materials, such as honeycombs and foams. However, these materials must combine damage tolerance characteristics with high resistance under both static and dynamic loads. Cork composites can be considered as an alternative material for sandwich components since cork is a natural material with some remarkable properties, such as high damage tolerance to impact loads, good thermal and acoustic insulation capacities and excellent damping characteristics for the suppression of vibrations. The experiments carried out in this investigation were oriented in order to optimize the specific strength of cork based composites for sandwich components. Static bending tests were performed in order to characterize the mechanical strength of different types of cork agglomerates which were obtained considering distinct production variables. The ability to withstand dynamic loads was also evaluated from a set of impact tests using carbon-cork sandwich specimens. The results from experimental tests showed that cork agglomerates performance depends on the cork granulate size, the type of reinforcing elements and the bonding procedure used for the cohesion with the matrix material.
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Authors: Maria Roseta, Carlos Pina dos Santos
Abstract: The interest of the study on the implementation of expanded agglomerated cork as exterior wall covering derives from two critical factors in a perspective of sustainable development: the use of a product consisting of a renewable natural material – cork – and the concern to contribute to greater sustainability in construction. The study aims to assess the feasibility of its use by analyzing the corresponding behaviour under different conditions. Since this application is relatively recent, only about ten years old, there is still much to learn about the reliability of its long-term properties. In this context, this study aims to deepen and approach aspects, some of them poorly studied and even unknown, that deal with characteristics that will make the agglomerate a good choice for exterior wall covering. The analysis of these and other characteristics is being performed by testing both under actual exposure conditions, on an experimental cell at LNEC, and on laboratory. In this paper the main laboratory tests are presented and the obtained results are compared with the outcome of the field study.
367
Authors: Sukhdeo R. Karade
Abstract: The growing environmental concern throughout the globe has led architects & engineers to design energy efficient buildings. Consequently, they are looking for building materials that can reduce the energy consumption in buildings to maintain the comfort level. Use of proper thermal insulating materials can reduce the energy required for heating or cooling of the buildings. Presently mineral wool and various foams are used for this purpose. Efforts are being made to use wastes in making thermal insulation materials so that the impact on environment can be further reduced. Cork granules are obtained as waste from the cork processing industries that make ‘bottle stoppers’ as a main product. These granules have a low density and could be used as lightweight aggregates for making concrete with low thermal conductivity. This article describes the physico-mechanical properties of lightweight cementitious composites made using cork granules. Further, environmental benefits of their application in thermal insulation of buildings has been discussed.
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