Liste des documents

Nombre total de résultats : 1847
Pertinence Titre A-Z Plus récents Plus anciens
10 25 50
Année de publication
et

Electrochemical behavior, characterization and corrosion protection properties of poly(bithiophene + 2-methylfuran) copolymer coatings on A304 stainless steel

Leila LAMIRI, Belkacem  (2018)
Publication

Polybithiophene (PBTh), poly(2-methylfuran) (PMeFu) and poly(bithiophene + 2-methylfuran) noted poly(BTh + MeFu) copolymer films were synthesized by electrochemical deposition on 304-stainless steel, from an acetonitrile (ACN) solution containing 10−2 m bithiophene, 10−2 m 2-methylfuran and 10−1 m lithium perchlorate (LiClO4), by cyclic voltammetry (CV) between 0 V and 2 V vs. SCE, with a scan rate of 50 mV · s−1. The copolymers coated were studied in a corrosive sulfuric acid medium (H2SO4 1 N) using the potensiodynamique polarization method and the electrochemical impedance spectroscopy (EIS). Copolymers coated characterization was performed using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The polarization curves show that the copolymer film formed on A304, shifts the corrosion potential towards more positive potentials. The presence of the poly(BTh + MeFu) improves the corrosion resistance of the metal in a corrosive medium, H2SO4. This protection against corrosion is caused by the barrier effect of the layer of copolymer, which covers the surface of the A304 stainless steel against the aggressive ions of the corrosive medium. Voir les détails

Mots clés : 2-methylfuran, bithiophene, copolymers, protection against corrosion, stainless steel.

Metallic Coating for Carbon Fiber Reinforced Polymer Matrix Composite Substrate

Amine REZZOUG, Said ABDI, Nadjet BOUHELAL, Ismail DAOUD  (2016)
Publication

This paper investigates the application of metallic coatings on high fiber volume fraction polymer matrix composites. For the grip of the metallic layer, a method of modifying the surface of the composite by introducing a mixture of copper and steel powder filler powders which can reduce the impact of thermal spray particles. The powder was introduced to the surface at the time of the forming. Arc spray was used to project the zinc coating layer.The substrate was grit blasted to avoid poor adherence. The porosity, microstructure, and morphology of layers are characterized by optical microscopy, SEM and image analysis. The samples were studied also in terms of hardness and erosion resistance. This investigation did not reveal any visible evidence damage to the substrates. The hardness of zinc layer was about 25.94 MPa and the porosity was around 6.70 percent. The erosion test showed that the zinc coating improves the resistance to erosion. Based on the results obtained, we can conclude that thermal spraying allows the production of protective coating on PMC. Zinc coating has been identified as acompatible material with the substrate. The filler powders layer protects the substrate from the impact of hot particles and allows avoiding the rupture of brittle carbon fibers. Voir les détails

Mots clés : Arc spray, coating, composite, erosion

Elaboration et caractérisation tribologique des dépôts composites à matrice métallique projetés thermiquement sur composites à matrice polymère

REZZOUG Amine (2018)
Thèse de doctorat

Les matériaux composites à matrice polymères CMP renforcés par des fibres de carbone sont très compétitifs grâce à leurs propriétés mécaniques et à leur une légèreté. Ceci, résulte par des modules et des résistances spécifiques supérieures à ceux des matériaux métalliques. Néanmoins, ils demeurent sensibles à l’usure et surtout aux impacts répétés des particules, d’où leur nécessité d’être protégés. Les procédés de projection thermique sont depuis quelques temps utilisés pour améliorer les propriétés de surface de ces composites à matrice polymère. Cependant, une mauvaise adhérence et une dégradation mécanique et thermique sont généralement constatées. Cette thèse s’inscrit dans le contexte de la protection des CMP, par le biais de dépôts réalisés par projection thermique avec un minimum d’impact sur le substrat. L'objectif principal de ce travail de thèse est d'étudier l'effet de la modification de la surface supérieure d’un substrat CMP sur la déposition d’une couche d’accrochage métallique qui permettra par la suite de déposer des couches de protection. Les CMP ont été élaborés avec différentes couches supérieures : couche en époxy pure, couche chargée en poudre de cuivre pur, couche chargée en mélange de poudre de cuivre et d'acier inoxydable et enfin une couche de tissu d'aluminium. Les couches surfaciques d’échantillons CMP ont été mises en œuvre pendant le processus de moulage sous-vide. La projection à l’arc a été utilisée pour déposer une sous-couche d’accrochage de zinc sur les CMP. Dans un deuxième temps, une étude a été abordée sur la faisabilité d’un revêtement à matrice métallique anti-usure par projection thermique à l’arc électrique FeCrNiBSi– W–Ti C et par cold spray Al-Al2O3. Des dépôts de sous-couches d’accrochage ont pu être obtenus et optimisés, sans dégradation thermique ou mécanique du composite. Dans le but de contrôler la qualité des revêtements obtenus, ces derniers ont subi une série de tests de caractérisation. Nous citons notamment l'adhérence, les propriétés mécaniques, la porosité, la microstructure, la morphologie et les faciès de rupture. Une fois optimisés, ces échantillons sont utilisés pour le dépôt des revêtements anti-usure et ont été évalués par le biais d’essais tribologiques et comparés au substrat sans revêtement.  Voir les détails

Mots clés : Composite à matrice polymère, dépôt métallique par projection thermique, tribologie, adhérence

Thermal spray metallisation of carbon fibre reinforced polymer composites Effect of top surface modification on coating adhesion and mechanical properties

A. REZZOUG, S. ABDI, A. KACI, M. YANDOUZI  (2018)
Publication

Thermal Spray TS processes are used to enhance the surface properties of Polymer Matrix Composites. However, poor adhesion and mechanical degradation are usually experienced. The main objective of this work is to investigate the effect of the modification of the top surface of Carbon Fibre Reinforced Polymer CFRP substrate on the TS deposition of metallic coatings. CFRP composite panels were manufactured with different upper layers I pure epoxy overflow layer, II pure copper powder filler layer, III mixture copper and stainless steel powder filler layer, and IV aluminium mesh layer. The top layers of the CFRP substrates were manufactured during the forming process. Arc Spray, one of the TS processes, was used to deposit zinc coating onto the manufactured CFRP panels. The substrates were sandblasted before the TS process to enhance the adhesion of the deposited zinc to the substrate. The quality of the coatings including adhesion and mechanical properties was investigated using tensile adhesion and bending test, respectively. The porosity, microstructure, morphology and surface fracture of the metallised CFRP coupons were characterized using optical and electronical microscopy techniques. The results obtained revealed that pure epoxy top layer did not resist to sandblasting prior to TS process, contrary to the substrates with fillers and mesh top layer. Moreover, the aluminium based mesh layer improved the adhesion strength by about 50 percent. Bending test results indicated that coating on CFRP composites decreased their mechanical properties. However, the use of a metallic mesh layer reduced the degradation effect of spraying. Voir les détails

Mots clés : CFRP composite, Zn coating, Arc spray, Filler layer, Adhesion strength

Contribution à l’analyse de l’endommagement des matériauxcomposites

REKBI Fares Mohamed Laid (2016)
Thèse de doctorat

The composite materials with an organic matrix have become a serious competitor to traditional materials in avariety of industrial and domestic areas. However the inter-laminar defects induced during implementation or duringstress are the main sources of its progressive damage. The promotion and use of these materials require the study of themechanical behavior and the various formes of damage. The main of this work is study the mechanical behavior anddamage of tubular composite materials with glass fiber and organic matrix obtained by the filament winding method.The experimental investigation is to cut specimens from composite tube for determination of mechanical tensileproperties and the toughness expressed by the energy release rate of the double cantilever beam specimens atdélamination, and the evolution of resistance with R curves. The aim of numerical study is the modeling of the damagewith element finit method from « ABAQUS » logiciel for determination of the energy release rate. Voir les détails

Mots clés : Composites materials, characterization, damage, fracture, delamination, Cracking

Experimental and numerical analysis of mode?I interlaminar fractureof composite pipes

F M L.REKBI, M.Hecini, A.KHECHAI  (2018)
Publication

A common industrial production process for composites is filament winding, widely used for the production of axially symmetriccomponents. In these composite components, delamination is a predominant failure mechanism. The current workfocuses on investigating experimentally the effect of the initial crack and fiber bridging length on the mode-I delaminationresistance curve (R-curve) behavior of various double cantilever beam (DCB) specimens. For this purpose, the magnitudesof initiation and propagation fracture toughness (GIC-init and GIC-prop) and the compliance C are calculated. DCB specimenswith a stacking sequence of [± 50]6 and various initial crack lengths of a0 = 33, 37, 59 and 70 mm are manufactured from areal composite pipe using filament winding process. In order to evaluate the critical energy release rate in mode-I, variousfracture tests are conducted on these specimens. The greatest bridging zone length dues to good penetration of two adjacentlayers of the delamination interface. Moreover, the results indicate that the fiber bridging length has a significant effect onthe GIC and the largest value of fiber bridging causes a large fracture toughness value. Finally, numerical simulations areperformed using finite element (FE) method and GIC-init measurements obtained experimentally are compared to the numericalfindings. The numerical displacements and GIC-init, calculated from the numerical displacements, are found to be in goodagreement compared to the experimental results. Voir les détails

Mots clés : Filament wound composite, Critical energy release rate, Propagation energy release rate, DCB specimen, Fiber bridging

Numerical study of parameters affecting pressure drop of power-law fluid in horizontal annulus for laminar and turbulent flows

Hicham Ferroudji, Ahmed Hadjadj, Ahmed HADDAD, Titus Ntow Ofei  (2019)
Publication

Efficient hydraulics program of oil and gas wells has a crucial role for the optimization of drilling process. In the present paper, a numerical study of power-law fluid flow through concentric (E = 0.0) and eccentric annulus (E = 0.3, E = 0.6 and E = 0.9) was performed for both laminar and turbulent flow regimes utilizing a finite volume method. The effects of inner pipe rotation, flow behavior index and diameter ratio on the pressure drop were studied; furthermore, the appearance and development of secondary flow as well as its impact on the pressure drop gradient were evaluated. Results indicated that the increment of the inner pipe rotation from 0 to 400 rpm is found to decrease pressure drop gradient for laminar flow in concentric annulus while a negligible effect is observed for turbulent flow. The beginning of secondary flow formation in the wide region part of the eccentric annulus (E = 0.6) induces an increase of 9% and a slight increase in pressure drop gradient for laminar and turbulent flow, respectively. On the other hand, the variation of the flow behavior index and diameter ratio from low to high values caused a dramatic increase in the pressure drop. Streamlines in the annulus showed that the secondary flow is mainly induced by eccentricity of the inner pipe where both high values of diameter ratio and low values of flow behavior index tend to prevent the secondary flow to appear. Voir les détails

Mots clés : Computational fluid dynamics (CFD) Power-law fluid Pressure drop Secondary flow

EFFECT OF filler METAL types ON MICROSTRUCTURE AND MECHANICAL BEHAVIOR OF HSLA-X70/304L SS DISSIMILAR WELDS

Mohammed Farid BENLAMNOUAR, Mohamed HADJI, Riad BADJI, Nabil Bensaid, Tahar Saadi, Yazid LAIB LAKSIR, Sabah Senouci  (2019)
Article de conférence

The aim of this study is to investigate the effect filler metal types on microstructure and mechanical properties of dissimilar welds between HSLA-X70 high strength steel alloy and 304L austenitic stainless steel produced by automatic tungsten arc welding (TIG). The weld joints were prepared using E304L, E316L, E2209L, and E7010 filler metal. The mechanical characteristics obtained from hardness, tensile and impact testing, were correlated to the optical and SEM microscopy, to establish a relationship between filler metal composition and the microstructures in different weld regions. It is concluded that E2209 filler metal lead to improve in the resilience characteristics and tenacity with a slight reduction in the ultimate tensile strength and hardness. Voir les détails

Mots clés : Dissimilar weld, HSLA-X70, 304L, microstructure, Mechanical property

Optimization of TIG Welding Process Parameters for X70-304LDissimilar Joint Using Taguchi Method

Mohamed Farid Benlamnouar, Mohamed HADJI, Riad BADJI, Nabil Bensaid, Tahar Saadi, Yazid Laib dit Laksir, Sabah Senouci  (2019)
Publication

The optimization of mechanical properties of the welded joints requires a statisticalapproach such as Taguchi experimental designs associated with experimental techniques andlaboratory characterizations. The aim of this work is to propose a method of optimization of themechanical performances of a TIG dissimilar welding of two grades of steels: a high strength lowalloy steel X70 and an austenitic stainless steel 304L. The experimental designs were chosenaccording to the Taguchi method L9. The metallurgical characterization includes opticalmicroscopy, SEM microscopy, EDX analyses and mechanical tests to establish a relationshipbetween welding parameters, microstructures and mechanical behavior in different dissimilar weldregions. The results showed that the hardness is more strongly related to microstructural evolutionthan tensile strength of dissimilar joint. It was found that gas flow is the main significant TIGwelding parameter affecting dissimilar weld characteristics. Voir les détails

Mots clés : hardness, tensile test, ANOVA, Dissimilar welds, Taguchi method

Annealing duration influence on dip-coated CZTS thin films properties obtained by sol-gel method

M.C. Benachour, R. Bensaha, R. Moreno  (2019)
Publication

The effect of annealing duration on structural and optical properties of dip-coated crystallineCZTS thin films was studied. The obtained samples were investigated by several techniques suchas XRD, Raman spectroscopy, SEM, UV–vis spectroscopy and Photoluminescence. Being con-firmed by Raman spectroscopy, XRD analysis reveals the formation of kesterite tetragonal phasewith preferential orientation along (112) direction. The grain size tends to increase as the an- nealing duration increases, a result confirmed by SEM. The last shows smooth, uniform, homo-geneous and densely packed grains. Optical measurement analysis reveals that layers have re- latively high absorption coefficient in the visible spectrum with a band gap reduction of1.62−1.50 eV which is quite close to the optimum value for a solar cell. The photoluminescence distinguishes broad bands that have maximums of intensity limited between 1.50 and 1.62 eV,corresponding to the optical band gap of the CZTS.Kesterite,Sol-gel,Thin-film,Dip-coating,CZTS,Photoluminescence Voir les détails

Mots clés : Kesterite, sol-gel, Thin-film, Dip-Coating, CZTS, Photoluminescence