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Majāz al Bāb, Tunisia

Gherissi A.,URMSSDT ESST Tunis | Cheikh R.B.,French National Graduate School of Textile Engineering | Devaux E.,National Engineering School of Tunis | Abbassi F.,URMSSDT ESST Tunis
Applied Mechanics and Materials | Year: 2012

In this study, we present the manufacturing process of two new composites materials in the form of long fibers of polylactic-acid (PLA) or polypropylene (PP), reinforced by cellulose whiskers microfibers loads. In order to evaluate the mechanical properties of these advanced materials, a several uniaxial tensile tests were carried outThe PP and the PLA have initially been spinning without the addition of cellulose whiskers microfibers. In order to study the effects of cellulose whiskers micro-fibers reinforcements in the Mechanical behavior of the PLA and PP filaments, we determinate the proprieties of these advanced material from the tensile results. For the PP composite filaments material case, the whiskers reinforcement increases Young's modulus and failure resistance, but it reduces the limit strength failure. For the PLA composites the addition of 1% wt of cellulose whiskers from the total volume fraction of the material, increase the Young's modulus more than 50% and a decrease of the failure resistance and the limit strength of composite. The obtained composites fibers are very rigid and brittle. What follows, that the addition of cellulose whiskers micro fibers in PP matrix, provides mechanical properties more convenient compared to the PLA matrix. © (2012) Trans Tech Publications, Switzerland. Source


Abbassi F.,URMSSDT ESST Tunis | Pantale O.,National Engineering School of Tarbes | Mistou S.,National Engineering School of Tarbes | Zghal A.,URMSSDT ESST Tunis | Rakotomalala R.,National Engineering School of Tarbes
Key Engineering Materials | Year: 2010

The numerical simulation based on the Finite Element Method (FEM) is widely used in academic institutes and in the industry. It is a useful tool to predict many phenomena present in the classical manufacturing forming processes such as necking, fracture, springback, buckling and wrinkling. But, the results of such numerical model depend strongly on the parameters of the constitutive behavior model. In the first part of this work, we focus on the traditional identification of the constitutive law using oriented tensile tests (0°, 45°, and 90° with respect to the rolling direction). A Digital Image Correlation (DIC) method is used in order to measure the displacements on the surface of the specimen and to analyze the necking evolution and the instability along the shear band. Therefore, bulge tests involving a number of die shapes (circular and elliptic) were developed. In a second step, a mixed numerical-experimental method is used for the identification of the plastic behavior of the stainless steel metal sheet. The initial parameters of the inverse identification were extracted from a uniaxial tensile test. The optimization procedure uses a combination of a Monte-Carlo and a Levenberg-Marquardt algorithm. In the second part of this work, according to some results obtained by SEM (Scaning Electron Microscopy) of the crack zones on the tensile specimens, a Gurson Tvergaard Needleman (GTN) ductile model of damage has been selected for the numerical simulations. This model was introduced in order to give informations concerning crack initiations during hydroforming. At the end of the paper, experimental and numerical comparisons of sheet metal forming applications are presented and validate the proposed approach. © (2010) Trans Tech Publications. Source


Abbassi F.,URMSSDT ESST Tunis | Gherissi A.,URMSSDT ESST Tunis | Zghal A.,URMSSDT ESST Tunis | Mistou S.,National Engineering School of Tarbes | Alexis J.,National Engineering School of Tarbes
Applied Mechanics and Materials | Year: 2012

Thin-walled textile-reinforced composite parts possess excellent properties, including lightweight, high specific strength, internal torque and moment resistance which offer opportunities for applications in mass transit and ground transportation. In particular, the composite material is widely used in aerospace and aircraft structure. In order to estimate accurately the parameters of the constitutive law of woven fabric composite, it is recommended to canvass multi-scale modeling approaches: meso, micro and macro. In the present investigation, based on the experimental results established by carrying out observations by Scanning electron microscope (SEM), we developed a micro-scale FEM model of carbon-fiber reinforced thermoplastic using a commercial software ABAQUS. From the SEM cartography, one identified two types of representative volume elementary (RVE): periodic and random distribution of micro-fibers in the yarn. Referring to homogenization method and by applying the limits conditions to the RVE, we have extracted the coefficients of the rigidity matrix of the studied composites. In the last part of this work, we compare the results obtained by random and periodic RVE model of carbon/PPS and we compute the relative error assuming that random model gives the right value. © (2012) Trans Tech Publications,Switzerland. Source

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