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Glaris P.,Thales Alenia | Glaris P.,CNRS Le Mans Institute of Molecules and Materials | Coulon J.-F.,ECAM RENNES Louis de Broglie | Dorget M.,Thales Alenia | Poncin-Epaillard F.,CNRS Le Mans Institute of Molecules and Materials
Composites Part B: Engineering | Year: 2015

Two routes for the grafting of fluorinated molecules to an epoxy resin were studied. The first one deals with the grafting of the liquid-state resin whereas the second one is focused on the grafting onto the solid-state resin. These grafting reactions were shown to be similar as studied through FTIR and XPS spectroscopies. However, it appears that the grafting onto the solid-state resin is limited by the curing advancement. N2 plasma-activation was used to solve this drawback and enhanced the grafting yield. This grafting improvement was mainly explained in terms of the surface wetting improvement and the attachment of nitrogen containing groups at the surface of the treated resin. © 2014 Elsevier Ltd. All rights reserved. Source


Glaris P.,Thales Alenia | Glaris P.,CNRS Le Mans Institute of Molecules and Materials | Coulon J.F.,ECAM RENNES Louis de Broglie | Dorget M.,Thales Alenia | Poncin-Epaillard F.,CNRS Le Mans Institute of Molecules and Materials
Composites Part B: Engineering | Year: 2015

Driving forces, responsible for the migration of a fluorinated additive added to a thermoset resin, toward the air/solid interface, were investigated. On this subject, the surface chemistry as characterized by XPS analyses was compared to theoretical models based on the rheological properties of the blend. It appears that the migration of the fluorinated molecules toward the surface cannot be described by a conventional diffusion model. A second model derived from the latter suits better to the experimental data and should be presented as another proof that additional motion forces drive the fluorine molecules migration in curing epoxy resin. ©2014 Elsevier Ltd. All rights reserved. Source


Skrzypczak A.,ECAM RENNES Louis de Broglie | Palicot J.,Supelec | Siohan P.,Orange S.A.
International Journal of Communication Networks and Distributed Systems | Year: 2012

The cognitive radio idea consists in the exploitation of spectral resources that are unused by a licensed user within a telecommunication standard. After having detected these available frequency bands by some sensing technique, our work takes a stand on the spectrum access problem. This issue requires some constraints on the modulation that must be taken into account. The flexibility in frequency offered by a multicarrier modulation (MCM) then represents a strong advantage which, in addition, can be fully exploited by the OFDM/OQAM modulation. Indeed, the fact that well localized frequency pulse shapes can be employed makes this modulation attractive for an optimised dynamic spectrum insertion. OFDM/OQAM and OFDM-based solutions are finally tested considering two different transmission scenarios. In both scenarios, it is shown that, for OFDM/OQAM, the time-frequency localisation criterion leads to a short prototype filter, satisfying a good compromise in terms of complexity/performance and also leads at the same time to a better peak-to-average power ratio (PAPR) distribution when compared to an analogue windowed OFDM scheme. © 2012 Inderscience Enterprises Ltd. Source


Glaris P.,Thales Alenia | Glaris P.,CNRS Le Mans Institute of Molecules and Materials | Coulon J.-F.,ECAM RENNES Louis de Broglie | Dorget M.,Thales Alenia | Poncin-Epaillard F.,CNRS Le Mans Institute of Molecules and Materials
Composites Part B: Engineering | Year: 2014

The aim of this work is to decrease the adhesion between a cured modified epoxy-based substrate and an in situ cured virgin epoxy-based piece. The effect of perfluorinated additives on the non-adhesion output is investigated through an adapted pull-off test. It appears that additive migration initiates the surface fluorination. Longer the fluorinated chain is, higher the surface fluorination is and weaker the adhesion strength is. The weak chemical affinity between these two epoxy resins is shown to be mainly responsible for these results leading to an adhesive rupture. © 2014 Elsevier Ltd. All rights reserved. Source


Diot G.,Institute Maupertuis | Koudri-David A.,CNRS Civil and Mechanical Engineering Laboratory | Walaszek H.,CETIM de Senlis | Guegan S.,CNRS Civil and Mechanical Engineering Laboratory | Flifla J.,ECAM RENNES Louis de Broglie
Journal of Nondestructive Evaluation | Year: 2013

Embedded welding defects, such as porosities and cracks, are generally formed during aluminium laser welding. It is challenging to test these defects with current non-destructive evaluation (NDE) methods. This work features the creation of defects and their study with the help of NDE methods. The chosen method should be able to detect porosities in lap-welded sheets of 5754 aluminium alloys. The welding process is described and the samples were first characterised with X-ray techniques to choose those containing defects of various sizes and densities. Secondly, these welds were tested with the Laser Ultrasonic Technique (LUT). The first results show that LUT gives defect signatures. Based on raw measurements only, our results show that it is difficult to give any precise description of the defects' size or position. To aid in the interpretation of the results, a frequency-bandwidth analysis has been performed because of the broadband nature of laser ultrasonic signals. © 2013 Springer Science+Business Media New York. Source

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