Browsing by Author "Mahdad, M'Hamed"

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    Comportement à l'impact à faible vitesse par indentation quasi-statique des stratifiés à matrice polypropylène
    (2018) Mahdad, M'Hamed; Ait Saada, A .; Belaidi, Idir
    Cet article présente une étude expérimentale pour évaluer la réponse aux chargements d'indentation quasi-statique à faible vitesse effectués sur des composites stratifiés. Une investigation expérimentale a été réalisée, comportant la conception d'un dispositif d'essai et la fabrication de deux types de composites stratifiés. La géométrie de l'impacteur est un hémisphère de 16 mm de diamètre. Des stratifies à base de matrice polypropylène et fibres d'acier et de verre-E (A/PP et V/PP) ont été confectionnés suivant les séquences d'empilement [0° 90°]2S. Des tests d'indentations statiques ont été effectués sur des stratifiés avec des faible vitesses de 1,7 mm/mn. Le mécanisme de défaillance est préférentiellement dominé par la déformation plastique de stratifié, le mode de pénétration résultant est fortement localisé. Les résultats obtenus ont montré que l'évolution de dommage affecte en premier la matrice thermoplastique, qui s'amorce par la suite au niveau des fibres et provoque arrachement/décollement notamment dans les zones de contact indenteur/plaque. L'amorçage des fissures étaient plus visible dans les stratifiés de composition V/PP comparativement aux stratifiés A/PP. Un modèle de plasticité MLT a été proposé, implémenté dans le code de calcul Abaqus/Explicit en utilisant la subroutine VUMAT. Des simulations numériques de validation ont été effectuées
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    Damage Modelling in Thermoplastic Laminates Reinforced with Steel and Glass Fibres under Quasi-Static Indentation Loading at Low-Velocity
    (Sage journals, 2019) Mahdad, M'Hamed; Ait Saada, Aicha; Belaidi, Idir
    This paper deals with experimental and numerical investigations of the composites damages with ductile and fragile reinforcement under quasi-static indentation loading. The main goal of the work is to increase the post-damage residual strength and ductility of thermoplastic composite. Two types of composite laminates with polypropylene (PP) matrix are tested: glass fibre laminate (GFPP) and steel fine wire mesh laminate (SWPP). The specimens are [0° 90°]2s stacking sequence and prepared by using a compression moulding technique. Quasi-static indentation tests were performed with two distinct penetration scales under low velocity (1.2 mm/min). The diameter of the hemispherical indenter is 16 mm. The failure mechanisms of composite layers were examined by the field emission scanning electron microscope (SEM). The results show that the failure mode of SWPP laminates is principally dominated by the plastic deformation component. In contrast, the GFPP laminate exhibits a fragile behaviour which is related to the fragile failure of glass fibres. In addition, the SEM shows that matrix cracking, fibre breakage, debonding and fibre pull out are the major damages observed around the indentation area. A model based on the combined use of plasticity, damage and fracture, was developed and applied to simulate quasi-static indentation behaviour and predict the resulting damage
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    Experimental and numerical evaluation of Quasi-Static Indentation behaviour of laminates with polypropylene matrix
    (Polish Society of Composite Materials, 2021) Mahdad, M'Hamed; Benidir, Adel; Belaidi, Idir
    This paper presents an analysis of the damage process of composite laminates subjected to low-velocity quasi-static indentation (QSI) load. The laminates were prepared using the compression moulding technique. The composites were made from orthotropic layers with E-glass or steel fibres and a polypropylene matrix. The quasi-static indentation tests were carried out at three levels of indentation energy under low-velocity. The experimental results reveal that using steel fibres increases the perforation threshold, which alludes to the importance of the fibre type in delineating damage regions. In contrast, the evolution of the damage and the perforation resistance of glass fibre reinforced laminates is somewhat different. A numerical model based on a finite element program was developed to understand the mechanisms of damage evolution in the laminates. It in-volves implementing the Matzenmiller-Lubliner-Taylor (MLT) damage model. A comparison between the experimental and numerical results was also made