Search results for " tecnologia."
showing 10 items of 1339 documents
The effect of alkaline treatment on mechanical properties of kenaf fibers and their epoxy composites
2015
Abstract In this work, kenaf fibers were pre-treated in a NaOH solution (6% in weight) at room temperature for two different periods (48 and 144 h). The chemical treatment of kenaf fibers for 48 h allowed to clean their surface removing each impurity whereas 144 h of immersion time had detrimental effect on the fibers surface and, consequently, on their mechanical properties. Untreated and NaOH treated kenaf fibers (i.e. for 48 h) were also used as reinforcing agent of epoxy resin composites. The effect of the stacking sequence (i.e. using unidirectional long fibers or randomly oriented short fibers) and the chemical treatment on the static mechanical properties was evaluated showing that t…
Manufacture of marine composite sandwich structures
2016
Abstract The aim of this chapter is to present the main processes of manufacture of composite sandwich structures used in marine applications. In the introduction, sandwich structure classification and properties and advantages/disadvantages in their uses are presented. In the second and third section, the main used technologies to made sandwich are, respectively, described and compared. Then, the goodness of these techniques is evidenced with the discussion of some experimental results obtained by the authors in their studies. The last section concludes with a thorough list of the future trends.
Fracture behavior and mechanical, thermal, and rheological properties of biodegradable films extruded by flat die and calender
2020
The development of biodegradable materials for tailored applications, particularly in the field of polymeric films and sheets, is a challenging technological goal as well as a contribution to help protect the environment. Poly(lactic) acid (PLA) is a promising substitute for several oil-based polymers; however, to overcome its thermal and mechanical drawbacks, researchers have developed solutions such as blending PLA with polybutylene adipate terephthalate (PBAT), which is capable of increasing the ductility of the final material. In this study, PLA/PBAT binary blends, with minimum possible content of nonrenewable materials, were examined from processing, thermal, morphological, and rheolog…
Chemical Modification of Nitrile to Oxazoline Functionality on a Styrene-Acrylonitrile Copolymer in the Melt
1998
Oxazoline is a very interesting functionality for reactive extrusion and other applications. In this paper, we report the possibility of chemically transforming nitrile group attached to a copolymer of styrene and acrylonitrile (SAN) to oxazoline group using 2-amino-ethanol (AE). The chemical modification of SAN with AE was done in the molten state. Among various catalysts tested, zinc acetate turned out to be the most efficient. The effects of the catalyst concentration, temperature and mixing on the overall kinetics were studied. The formation of the expected oxazoline functionality was confirmed by infrared spectroscopy and by reacting with 1-naphthylacetic acid. The reaction between the…
Three-Point Flexural Behaviour of GFRP Sandwich Composites: A Failure Map
2010
In this work, the failure mechanisms of GFRP/PVC foam core sandwich structures subjected to three-point bending are analysed. By varying the skin thickness (t ) and the span length between supports (l), experimental tests were carried out in order to find the relationship between the geometrical configuration of the sandwiches and the failure mechanism. By plotting failure mechanism on a graph of l against t , a failure map was created identifying the three typical failure mode regions of these sandwiches. The graph clearly shows the failure mode corresponding to each combination of l and t . To help optimise the use of these sandwich beams as structural elements, a theoretical failure mode…
Effect of ultraviolet and moisture action on biodegradable polymers and their blend
2020
In this work, the suitability of polylactic acid (PLA), polybutylene adipate terephthalate (PBAT) and PBAT/PLA blend samples to outdoor applications were investigated in terms of mechanical, morphological and visual properties in presence of ultraviolet action and water, finding that PLA in particular can be actually considered for such applications.
New patent on nanomaterials for preserving stone and wood structures
2013
Nowadays, we recognize the need for a renewed commitment to the questions posed by the contemporary city to imagine new constructability scenarios paying attention to energy efficiency and cost saving, in order to obtain the recovery of identity of a city, achieving efficiency and effectiveness of the results. This paper focuses on developing effective strategies, based on sustainability and policies applicable to the built environment. Scientific experiences of the Author, demonstrated by scientific and technological patents, regarding the implementation projects on Nanomaterials, nanostructured inorganic oxides, and more par-ticularly titanium sesquioxide and silicon, show that it is poss…
Partial joint processing with efficient backhauling using particle swarm optimization
2012
In cellular communication systems with frequency reuse factor of one, user terminals (UT) at the cell-edge are prone to intercell interference. Joint processing is one of the coordinated multipoint transmission techniques proposed to mitigate this interference. In the case of centralized joint processing, the channel state information fed back by the users need to be available at the central coordination node for precoding. The precoding weights (with the user data) need to be available at the corresponding base stations to serve the UTs. These increase the backhaul traffic. In this article, partial joint processing (PJP) is considered as a general framework that allows reducing the amount …
Multicell power allocation method based on game theory for inter-cell interference coordination
2009
As a new technology, coordinated multipoint (CoMP) transmission is included in LTE-Advanced study item. Moreover, the network architecture in LTE-Advanced system is modified to take into account coordinated transmission. Under this background, a novel power allocation game model is established to mitigate inter-cell interference with cellular coordination. In the light of cellular cooperation relationship and centralized control in eNodeB, the power allocation in each served antenna unit aims to make signal to interference plus noise ratio (SINR) balanced among inter-cells. Through the proposed power allocation game algorithm, the users' SINR can reach the Nash equilibrium, making it feasib…
On the influence of the initial ramp for a correct definition of the parameters of fractional viscoelastic materials
2014
Creep and/or Relaxation tests on viscoelastic materials show a power-law trend. Based upon Boltzmann superposition principle the constitutive law with a power-law kernel is ruled by the Caputo's fractional derivative. Fractional constitutive law posses a long memory and then the parameters obtained by best fitting procedures on experimental data are strongly influenced by the prestress on the specimen. As in fact during the relaxation test the imposed history of deformation is not instantaneously applied, since a unit step function may not be realized by the test machine. Usually an initial ramp is present in the deformation history and the time at which the deformation attains the maximum …