Behaviour of Materials

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作者: Habib Achache, Benali Boutabout, Djamel Ouinas
摘要: This paper presents a numerical method for the evaluation of the stress concentration factor (SCF) in three dimensional laminated composites under mechanical loads. The proposed method uses the finite element formulation. The composites materials based on the epoxy matrix and reinforcing fibers are extensively used in aircraft structures due to their high specific characteristics. However, the withstanding of composite structures can be significantly reduced by the addition of geometric singularities, such as perforations or notches. To Analyses the stress concentration around geometrical notches, several studies as analytical, numerical and experimental techniques are available. The stress distribution in a laminated composite plate with the presence of a circular hole was investigated using the finite element method. In order, the results obtained by this study are compared with those reported in literature. The aim of this analysis is to evaluate numerically the factor of stress concentration under the influence of several parameters such as fibers orientation, the mechanical characteristics of composites and the distance between notches of cross-laminated.
作者: Kamal Ait Tahar, R. Bahar
摘要: Currently, the composite materials make important great strides, considering their high mechanical properties. The studies relating to the conceptual, technical aspect and modeling of their mechanical behavior are more than desirable. The mechanical properties of the composite material depend on several factors as the nature of fibers, the fiber/matrix ratio, compatibility, homogeneity... In this study, we present the results of an experimental analysis of the behavior of the composite material, under a static and a dynamic loading. The composite material is composed respectively of the glass and metal fiber reinforcement. A various dimensions of the mesh are considering. The resin used is polyester Resow 55 E. The dynamic test ( Knoop test) is carried out on various specimens made up of an polyester resin RESOW 55 E reinforced with varied powder nature. It makes it possible to measure the hardness of composite materials. The analysis of the results shows clearly that the mechanical properties are strongly influenced by the dimensions of the elementary mesh of the fiber grid reinforcement. Based on experimental results, a Weibull modulus has been established for each specimen.
作者: C. Aribi, B. Bezzazi, A. Mir
摘要: The performances of composite materials are influenced by the properties of the matrix used. The latter ensures the desired form and the protection of the reinforcements against the external attacks. This work comprises a comparative study between laminates developed with different matrices in epoxy resin. Their characterization has to choose the best matrix able to give best results in static and dynamic tests. The resins used are provided by Granitex Algéria and which are primary Médapoxy STR resins, Médapoxy inject 812 and Médapoxy Al resin. Hence, the results of tensile tests prove a fragility of the AL resin which influences the maximal constraint of traction compared to the STR primary resin. Furthermore, Inject 812 resin shows very limited mechanical properties due to the changes of the epoxy network with the addition of diluents which has significantly decreased its viscosity.
作者: Abdel Bakkali, L. Azrar, A.A. Aljinadi
摘要: In this paper, the effective properties of magnetoelectroelastic heterogeneous materials with ellipsoidal multi-inclusions are modeled and numerically investigated. The modeling is based on the integral equation that takes into account the multi-coated effect as well as the magnetoelectroelastic interfacial operators and global and local concentration tensors. Various types and kinds of coatings can be considered. The effective properties are predicted based on various micromechanical models such as Mori-Tanaka, Self-Consistent and Incremental Self-Consistent. These properties are presented in terms of the volume fractions of the multi-coated inclusions, thicknesses of the coatings, type and kind of inclusions.
作者: Djamel Bensahal, Mohamed Nadir Amrane, Mounir Kharoubi
摘要: The paper presents an analysis of the damping of laminated beams with four different stacking sequences. The experimental investigation was conducted using tensile cyclic tests for different laminates studied. The impulse technique was chosen to perform modal analysis of the ease of implementation and quickness of the test. The numerical analysis is performed by the finite element method using beam element. The difference between strain energies for both cases damaged and undamaged are calculated by the finite element method. The structural damping of the different beams is evaluated from these energies. The decrease in frequency for different rates of loading shows the loss of stiffness for all materials studied.
作者: N. Boualem, A. Raid, M.A. Ghaffor, A. Tlemçani, M. Derrar
摘要: Thermal spraying is a process for surface coating by projecting a material in powder or in wire form on a material with a previously prepared surface. The materials used in our study are 5086 aluminum alloy and 304 L stainless steel with various surface qualities: polished 120, mirror polished and sandblasted. The projection powder is a combination of "ceramic-metal" WC-Co whose average grain size is 30 microns. The layers thicknesses obtained after 3 passes vary between 90 and 120 microns depending on the operating conditions: gas protection, temperature and surface condition. Indentation tests at the substrate-layer interface and micrographic sections revealed the roughness importance to allow a better layers grip.
作者: B. Boukert, A. Benkhedda, S. Bergheul
摘要: In recent years composite materials are widely used in the aerospace industry. The advantages of these materials are derived from their high strength, rigidity and lightness. More importantly, they have the potential to reduce the cost of construction, while improving structural reliability and increasing safety. Aircraft structural parts made of composite materials with polymeric matrix, subject to variables conditions and severe environments, require a good knowledge of their behavior under humidity and temperature. The matrix is very sensitive to these parameters. A degradation of properties is then observed [1-1.
作者: Mounir El Achaby, El Mokhtar Essassi, Abou El Kacem Qaiss
摘要: The aim of this work is to prepare, by extrusion, blends of polypropylene (PP)/styrene-ethylene-butadiene-styrene-g-maleic anhydride (SEBS-g-MA) at the ratios of 100/0, 95/5, 90/10, 85/15 80/20. Then, a amount of 10 wt% of calcium carbonate (CaCO3) was added to each polymer blend to prepare (PP/SEBS-g-MA)/CaCO3 composites with effective ratios of (100/0)/10 (95/5)/10, (90/10)/10, (85/15)/15 and (80/20)/10. Morphological and tensile properties of PP/SEBS-g-MA, PP/CaCO3 and (PP/SEBS-g-MA)/ CaCO3 were evaluated and compared. It was found that the presence of SEBS-g-MA improves the particle dispersion and interfacial adhesion. The tensile properties of PP polymer were affected by addition of SEBS-g-MA and/or CaCO3. Indeed, the addition of only SEBS-g-MA the youngs modulus and tensile strength of PP were remarkably decreased and the elongation at break was significantly increased. In contrast, the PP/ CaCO3 composites shows improved youngs modulus and tensile strength and reduced elongation at break in regard to neat PP. A balance between these selected properties was found in (PP/SEBS-g-MA)/CaCO3 composites, while the youngs, tensile strength and elongation at break were together increased. .
作者: Hichème Ferdjani
摘要: The elastostatic antiplane problem of a Dugdale crack at the interface of two different materials is considered. Using integral transform, the problem is reduced to a single integral equation. The integral equation is solved numerically. The evolution of the crack for different values of the physical and geometrical parameters of the problem is studied. A comparison between the results obtained with the Griffith and Dugdale models is presented.