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Karray M.,Unite de letat solide | Karray M.,University of Maine, France | Triki A.,Laboratoire des Materiaux Composites | Poilane C.,University of Maine, France | And 3 more authors.
Polymer Composites | Year: 2016

In this work, we undertook a comparative study of the dynamic dielectric analysis of two unidirectional epoxy composites: flax-fiber-reinforced epoxy and flax/carbon-fiber-reinforced epoxy (FCFRE). In both composites, three relaxation processes were identified. The first one is the water dipoles polarization imputed to the presence of polar water molecules in flax fiber. The second relaxation process associated with conductivity occurs as a result of the carriers charges diffusion noted for high temperature above glass transition and low frequencies. As for the third dielectric relaxation associated with the interfacial polarization effect is attributable to the accumulation of charges at the fibers/matrix interface. The presence of two carbon plies in the reinforcement gives rise to two interfacial polarization effects in the FCFRE composite. The analysis of the Maxwell-Wagner-Sillars and the water dipoles polarizations using the Havriliak-Negami model revealed that the presence of two plies of carbon can locally decrease the adhesion of flax fibers in the matrix. This analysis was supported by the thermal properties using a differential scanning calorimety and the mechanical properties using a short beam shear test. © 2014 Society of Plastics Engineers. Source


Triki A.,Laboratoire des Materiaux Composites | Karray M.,Unite de letat solide | Karray M.,University of Maine, France | Poilane C.,University of Caen Lower Normandy | And 2 more authors.
Journal of Electrostatics | Year: 2015

Dielectric measurements were performed on alkali treated flax fibers reinforced epoxy composites in the frequency range 0.1 Hz-1 MHz and the temperature range 40-170 °C. Two common dielectric relaxations were observed for all composites. The first one appearing at low temperatures was attributed to the water dipoles polarization due to the hydrophilic character of flax fibers. The second one observed at high temperatures was identified to the interfacial polarization. Analysis of this latter using the Havriliak-Negami model showed an improvement of the fibers/matrix adhesion by these alkali treatments. The best adhesion was obtained by the leaching treatment. © 2015 Elsevier B.V.. Source


Triki A.,Laboratoire des Materiaux Composites | Karray M.,Unite de letat solide | Poilane C.,University of Caen Lower Normandy | Picart P.,University of Maine, France | Gargouri M.,Unite de letat solide
2014 North African Workshop on Dielectric Materials for Photovoltaic Systems, NAWDMPV 2014 | Year: 2014

Surface treatment of woven flax fibers was investigated as means of improving their adhesion in epoxy matrix. Flax fibers were treated in two ways : (i) with enzymatic treatments using pectinase enzymes and (ii) with pectinase enzymes/detergent, respectively. For this reason, dielectric measurements were performed in the frequency range from 10-1 Hz to 106 Hz and temperature interval from 40 °C to 200 °C. Studies of dielectric relaxations in these composites revealed the presence of three relaxation processes namely the orientation polarization imputed to the presence of polar water molecules in flax fibers, the relaxation process associated with conductivity occurring as a result of the carriers charges diffusion noted for high temperature above glass transition and low frequencies, and interfacial polarization effect or Maxwell-Wagner-Sillars (MWS) relaxation that is attributable to the accumulation of charges at the flax fibers/epoxy resin interfaces. Analysis of this latter using the Havriliak-Negami model revealed that the adhesion fibers/matrix was improved by the addition of the detergent treatment to the enzymatic one. © 2014 IEEE. Source


Ben Amor I.,Laboratoire des Materiaux Composites | Rekik H.,Laboratoire des Materiaux Composites | Kaddami H.,Laboratoire Of Chimie Bioorganique Et Macromolecualire | Raihane M.,Laboratoire Of Chimie Bioorganique Et Macromolecualire | And 2 more authors.
Journal of Composite Materials | Year: 2010

The dynamic dielectrical analysis of short palm tree lignocellulosic fiber-reinforced polyester composites was carried out with special reference to the effect of fiber orientation, frequency, and temperature. Measurements were performed in the temperature range 40-200°C and in the frequency range 1-100 kHz. Three relaxations processes were identified, namely the orientation polarization imputed to the presence of polar water molecules in palm fiber, the relaxation process associated with conductivity occurring as a result of the carriers charges diffusion noted for high temperature above glass transition and low frequencies, and the interfacial or Maxwell-Wagner-Sillars relaxation that is attributable to the accumulation of charges at the palm fibers/polyester interfaces. The orientation of the fiber can strongly influence the dielectrical properties and interfacial polarization processes in composites. © 2010 The Author(s). Source


Triki A.,Laboratoire des Materiaux Composites | Omri M.A.,Laboratoire des Materiaux Composites | Guicha M.,University of Monastir | Hassen M.B.,University of Monastir | And 2 more authors.
IOP Conference Series: Materials Science and Engineering | Year: 2013

Dielectric measurements and tensile testing of polyester/natural fibres (Alfa/wool) and thermo binder fibres (Pe/Pet) composites were investigated in order to study the adhesion of the fibres in the polyester matrix. Two composites #1 and #2 having 17:1:2 and 17:2:1 as a relative fraction of alfa/wool and thermo binder (Pe/Pet), respectively, have been characterized in this study. The obtained results revealed that the fibres adhesion in the matrix was better in the composite #1 than in the composite #2. Indeed, the analysis of the interfacial or Maxwell-Wagner-Sillars (MWS) polarization intensity, using the Havriliak-Negami model, has shown a lower intensity and the tensile testing exhibited a higher Young modulus in the composite #1. So the thermo binder fibres improve this adhesion. Source

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