Publications Scientifiques
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Item Mechanical properties and low-velocity impact analysis of camel hair and hybrid camel hair/flax fibre-reinforced epoxy(Springer, 2024) Bencheikh, Amir; Nour, Abdelkader; Casimir, Jean B.; Aguib, Salah; Gherbi, Mohammed T.; Attia, Nourhane; Djedid, Toufik; Baali, Besma. R.; Aribi, ChouaibComposite plates structures are subjected to many damage problems under low-velocity impacts such delamination and matrix cracking, in order to know the importance of hybridisation on improving mechanical properties. This study explores the low-velocity impact behaviour of two composites: one reinforced with camel hair fibre/epoxy (CHF/Epoxy) and the other with a hybrid of camel hair and flax fibres camel hair fibre–flax fibre/epoxy (CHF-Flax/Epoxy). Static tests (tensile, compression, and bending) were conducted to characterise the mechanical properties of the composites. Impact tests were performed using a drop weight impact machine at three energy levels (3, 7, and 20 J). Particularly, the hybrid composite plate (camel hair fibre/epoxy) exhibited superior mechanical properties in static tests, leading to enhanced impact resistance compared to the composite plate (camel hair fibre/epoxy). Additionally, a numerical study was conducted using a 3D finite elements model. The Hashin criteria and the progressive damage model were used to predict intralaminar damage, and surface-based cohesive behaviour with quadratic stress failure criteria was used to predict delamination. The progressive damage model was coded and its implementation is conducted with a user-defined material subroutine (VUMAT) for Abaqus/Explicit. The damage mechanism and energy dissipation were observed at each energy level. Matrix cracking occurred first, followed by delamination. The 3D damage model was able to simulate the damage initiation and damage evolution until failure. The results of the model showed good agreement with experimental results in term of force, displacement and energy dissipation curves.Item Jets of discontinuously shear thickening suspension(2020) Meloussi, Mounir; Kuzhir, Pavel; Aguib, SalahIn the present work, jets of discontinuously shear thickening (DST) suspension emerging from a vertical pipe have been experimentally studied. The suspension flows through the pipe under gravity at nearly constant flow rate and the stress field in the jet is mostly extensional with the stress levels governed by gravitational forces. The dynamics of the jet was recorded with a high-speed camera at 300 fps, then the recorded videos were discretized into pictures and carefully analyzed with a written and executed program in MATLAB, based on image processing. The suspension is a concentrated mixture of calcium carbonate (CC) microparticles dispersed in water at 68% volume fraction with addition of different concentrations of polyamide (PA) microfibers of 700μm x 15 μm in size. The CC suspension solely exhibits strong DST behavior characterized by a viscosity divergence above a critical stress. At a given flow rate, depending on the jet length (distance between the pipe outlet and a point where the jet hits the experimental table), different behaviors are observed varying between stable viscous thread to coiling instability and elastic instabilities with periodic rupturing of the jet ascribed to achievement of the critical stress of the DST onset under extensional deformations. Addition of fibers mainly stabilizes the jets and this effect is still not fully understood and perhaps depends on the flow-induced orientation of fibers under extensional flow, increasing extensional viscosity. In this communication we will discuss in detail different regimes and present experimental correlations between the fiber concentration and dynamic parameters of the jet instability (wavelengths, lateral oscillation amplitudes, etc.)Item Dynamic characterization of the magnetomechanical properties of off axis anisotropic magnetorheological elastomer(De Gruyter Open, 2022) Bendjeddou, Walid; Aguib, Salah; Chikh, Noureddine; Nour, Abdelkader; Djedid, Toufik; Kobzili, Lallia; Meloussi, MounirThe use of magnetorheological elastomers in the mechanical and acoustic fields, by the automotive, aeronautical, and building industries, is currently developing strongly and rapidly. The perfect understanding of the capacity of smart insulation based on the absorption of the vibratory waves by magnetorheological elastomers materials passes by the knowledge of their dynamic mechanical behavior. In this present work, we have characterized the dynamic mechanical properties of the magnetorheological elastomer off axes anisotropy by the inclination, of different angles (15°, 30°, and 45°), of the pseudo-fibers of the iron particles formed by the application of a magnetic field at different intensities using an optimal loading rate of 30%. The rubber specimens were prepared by mixing micron-sized iron particles dispersed in room temperature vulcanized (RTV) silicone rubber by solution mixing. The experimental results obtained show a clear dependence of the effect of inclusion of ferromagnetic chains on the magnetomechanical properties. It is observed that the mechanical properties are better when applying a magnetic field of 0.6 T with an angle of inclination of 45°. The improvements added in this work could be useful in several industrial applications, such as automotive, aeronautic through adaptive control of damping and vibration levelItem Jet instability of suspensions of different shaped particles exhibiting discontinuous shear thickening(Society of Rheology, 2022) Meloussi, Mounir; Schaub, S.; Ciffreo, A.; Aguib, Salah; Kuzhir, P.This work is devoted to the detailed study of jet instability occurring in concentrated aqueous mixtures of calcium carbonate (CC) isotropic-shaped particles and rigid polyamide (PA) fibers. These mixtures exhibit very sharp discontinuous shear thickening (DST). The jets were subjected to a free fall under gravitational stretching at a constant flow rate. In the absence of PA fibers, we observed relatively strong lateral oscillations occurring for jet lengths L ≳ 6 cm and accompanied by small periodic undulations of the jet diameter. Two-dimensional Direct Fourier Transform analysis reveals approximately linear dispersion relations for propagation of lateral oscillations and diameter undulations with similar wave speeds ∼ 1 m / s. This instability is ascribed to complex rheological behavior in an extensional flow above the DST transition. Theoretical modeling reveals abrupt jumps of the tensile stress along the jet likely leading to fluctuation of longitudinal and transverse velocity fields within the jet perceived through jet diameter and centerline undulations. The addition of PA fibers to CC suspension damps lateral oscillations but favors ruptures along the jet. This is tentatively explained by the interplay between growing lower and decreasing upper DST threshold stresses with increasing fiber volume fraction φ f along with the thinning of the jet diameter down to the size of fiber flocs. Quantitatively, the stabilizing effect of PA fibers is manifested through an abrupt decrease in the lateral drift amplitude at φ f ≳ 0.75 vol %Item Experimental analysis of the tensile behavior of a hybrid composite beam with adjustable mechanical properties(Springer, 2022) Aguib, Salah; Chikh, Noureddine; Settet, Ahmed tidjani; Nour, A.; Meloussi, Mounir; Djedid, T.Magnetorheological elastomer beam samples were tested in uniaxial tension in magnetic fields of different intensities up to the final rupture. The samples deformed nonlinearly. Their maximum elongation reached 70% and the tensile strength increased by 120% with growing intensity of magnetic field appliedItem Analysis of buckling stability behavior of hybrid plate using Ritz approach and numerical simulation(Elsevier, 2021) Aguib, Salah; Chikh, N.; Kobzili, L.; Djedid, T.; Nour, A.; Meloussi, MounirIn this article, we studied the instability phenomenon of plate buckling made of steel (E36-S355), and magnetorheological elastomer subject to compression loading. The study of the magnetic field intensity influence on the buckling instability of compressed hybrid plates is done by a mathematical development using the Ritz approach and by a numerical simulation under the Abaqus software. The obtained results show clearly that we can control the instabilities of the adaptive smart plate’s behavior by the magnetic field, and the orientation angle of pseudo-fibers formed by the iron particles; depending on the variation of the angle direction of the magnetic fieldItem Measurements and identification of smart magnetomechanical elastomer composite materials properties in shear mode(Institute of Physics Publishing, 2019) Nedjar, Ali; Aguib, Salah; Djedid, Toufik; Nour, Abdelkader; Meloussi, MounirMagnetorheological elastomer composite materials (MRE) are a new class of intelligent active materials composed of ferromagnetic particles, of micrometric size, dispersed in a silicone elastomer matrix, which exhibit variable stiffness and damping properties which are modifiable under the application of an external magnetic field. Currently, these devices are primarily used in automotive and building applications, but they can easily be adapted to meet the requirements of aerospace applications. The development process and experimental characterization needed to evaluate the active control performance of this material have been made. This is done by characterizing the mechanical properties as a function of the magnetic field, as a function of the excitation frequency and as a function of the different percentage of ferromagnetic particles loading. An example of application of this material in aeronautics is also presented