Publications Scientifiques

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Author: search.filters.author.Safi, BrahimHas files: No

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    Experimental and numerical investigation of impact behavior in honeycomb sandwich composites
    (SAGE, 2024) Djellab, Amira; Chellil, Ahmed; Lecheb, Samir; Safi, Brahim; Mechakra, Hamza; Houari, Amin; Kebir, Hocine; Madani, Kouider
    This paper presents an experimental and numerical study on the low-energy impact fatigue and bending behavior of sandwich panels reinforced with composite laminate glass and carbon fabric facesheets, supported by a honeycomb core made of Nomex. The crushing behavior of honeycomb sandwich specimens subjected to the impact test was compared and discussed. Our results indicate that the carbon composite facesheets have a significant effect on the impact, resulting in an increase in impact resistance and a 157.14% increase in crack depth in the elastic region compared to glass facesheets reinforcement. This increase serves as an indicator of the laminate's ability to resist damage initiation and impact fracture mechanisms. Also, an increasing in flexural strength about 45.72% was observed in carbon facesheets honeycomb specimens compared to glass facesheets reinforcement. Microscopic illustration of the damaged honeycomb sandwich specimens was conducted to evaluate the interfacial characteristics and describe the damage mechanics of the composite facesheets and core adhesion under the impact test. The numerical approach proves to be efficient in terms of accuracy and simplicity compared to existing methods for predicting the damage mechanisms of honeycomb sandwich structures. It was noted that results of numerical study show best agreements with experiment results and the model can be used to predict the low-energy impact fatigue.
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    Physico-mechanical characterization of an ecological marble based- mortar
    (STEF92 Technology, 2023) Chahour, Kahina; Safi, Brahim
    Disposal of waste generated by the industries remains one of the major challenges to preserve the environment. Indeed, the use of industrial waste and by-products in construction is an important advantage to conserve natural resources. For this reason, several studies have focused on the use of marble waste in construction as recycled aggregate or fine powder. The work aim is to investigate the physical properties and mechanical behavior of eco-friendly mortar made with marble powder. The experimental study consists in studying the effect of cement substitution by marble powder (0%, 5% 10% and 20% wt.) on the fluidity and mechanical properties (Flexural strength, compressive strength and mechanical behavior) of elaborated mortars. The results show that it is possible to manufacture an ecological mortar having the good mechanical characteristics with marble powder and with local materials with the same basic components as a normal mortar and thus obtaining the same characteristics as those known internationally. The content amount of the marble powder as an addition to the cement is satisfactory to produce an ecological mortar with good resistance and better cement economy.
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    Effect of nanosilica-doped superplasticizer on the properties of cement mortars
    (STEF92 Technology, 2023) Safi, Brahim; Mechakra, Hamza; Saidi, Mohammed; Lecheb, Samir
    Recently, nanotechnology has attracted a considerable scientific interest due the potential new uses of non-particles, which can improve the properties of cement mortars or concretes, such as Nanosilica. Nanoparticles, like those of nanosilica, have been shown to have unique physical and chemical properties different from those of conventional cement additions. Nanosilica was used either to replace part of the cements or as an addition to improve the performance of the cement such as accelerating the hydration of the cement phases. This work investigates the effect of nanosilica adding to superplasticizer on fresh and hardened properties of cement mortars. For this, three superplasticizer types of three different firms doped with nanosilica (NS) at 1.5% wt. of superplasticizer (SP) to estimate the effect of nanosilica-based superplasticizer on the properties of cement mortars in the fresh and hardened state. An experimental study was conducted to evaluate the three SP based on NS on fresh and hardened properties. Our results show that nanosilica is compatible with the three superplasticizer, what is remarkable on the mortars in the fresh state, with a good workability which is between (24cm and 28cm) and a total absence of segregation which acts on the mechanical properties of the self-consolidating mortar in (3,7 and 28 days).
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    Rheological and Physic-mechanical study of metallurgical cements based on Nano-silica combined with blast furnace slag
    (Matrix Rom, 2020) Bouali, Khaled; Daoui, Hakim Mohammed; Safi, Brahim
    Această lucrare tratează comportamentul reologic și mecanic al cimenturilor metalurgice bazate pe nano-silice (NS) combinate cu zgură de furnal (GBFS). Un studiu experimental a fost realizat cu un raport constant de apă / liant (A / L) de 0,5 utilizat pentru toate mortarele studiate. Pentru a utiliza maximul GBFS și a scădea consumul de ciment, diferitele conținuturi (36% și 66% .wt) GBFS și 3% .wt de NS au fost alese și adăugate la Portland Cement (PC). Au fost efectuate teste reologice pe paste cimentate și au fost efectuate teste mecanice pe mortare elaborate cu ciment metalurgic studiat. Rezultatele obținute arată că pastele de ciment cu 3% NS fără GBFS au fost cele mai puțin vâscoase și au un efort de forfecare mai scăzut, cu o workabilitate acceptabilă în comparație cu alte paste de ciment. Cu toate acestea, în prezența GBFS, pastele de ciment devin mai vâscoase, ceea ce face ca debitul să fie mai dificil, cu o forță de forfecare mai mare la debit. De asemenea, rezultatele au arătat, în comparație cu mortarele de control GBFS, că încorporarea unei mici cantități de NS în ciment în prezența GBFS crește în mod remarcabil rezistența la compresiune la 28 și 90 de zile. Incorporarea a 3% în greutate NS în pastele de ciment cu un conținut de GBFS de 36% și 66% în greutate a dat valori ale rezistenței la compresie de foarte mare 90 zile (71,70 și 56,30 MPa). NS și LHF pot reduce în mod remarcabil porozitatea matricei de ciment și cresc densitatea acestuia, ceea ce explică de asemenea rezistența ridicată la rezistența la compresiune.
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    Highlighting of the distribution effect of steel hook fibers at low and high dosage on the flexural strength of self-compacting mortars
    (2022) Kheddache, Lynda; Aribi, Chouaib; Chahour, Kahina; Safi, Brahim
    In this paper, the distribution effect of low and high dosage steel hooked fibers on the flexural strength and mechanical behaviour of self-compacting mortars is investigated. Specimens were shaped so as to distribute the steel hooked fibers in three layers at different dosage (volume fraction of 0.25%, 0.40% and 0.50% respectively for each layer). The obtained results show that the mechanical behaviour in flexural and the flexural strength of the reinforced self-consolidating mortars were significantly influenced and directly depending on the fibers distribution per layer. This finding clearly shows the importance of the steel fibers distribution in the cement matrix during implementation has a major influence on the mechanical behaviour of mortars reinforced with metal fibers. The maximum value recorded is 14.5 MPa for the high dosage. The distribution of the steel fibers by layer made it possible to obtain a strength gain of 71.83% at low dosage and more than 100% at high dosage
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    Strength development of fiber reinforced selfcompacting concrete (RFSCC): Temperature effect on mechanical properties
    (2014) Safi, Brahim
    The strength development of Fiber Reinforced Self-Compacting Concrete (FRSCC) was investigated in this work. The variable is the heat curing at different temperatures (20°C and 60°C) applied at 7 and 14 days of curing of concretes studied. Two temperatures 20 and 60 °C were applied to samples with intermediate levels (depending on the drying method applied to precast concrete) for 18 hours in total. In this study, a Portland cement (CEMII), limestone fillers were used in the binders of FRSCC and the steel fibers are also used as reinforcement for concrete. The results show that the compressive strength to 14 days of concretes studied, increases with heating (60 °C) compared to that measured at 20 °C. Also, values of compressive strength of FRSCC at 14 days that are best to those obtained without 28 days curing treatment. Indeed, the compressive strength values of treated concretes (14jours) obtained are 15% and 25% respectively obtained for fibers reinforced self-compacting concretes made with 1.5% of steel fibers
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    Influence of polycarboxylate superplasticizer on hydration and rheological properties of cement pastes containing different cements
    (2014) Oubraham, Chahrazed; Benmounah, A.; Samar, Mohamed Faouzi; Safi, Brahim
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    Behavior of mortars hydraulic and organic matrix in aggressive environments
    (2013) Saidi, Mohammed; Safi, Brahim; Samar, Mohamed Faouzi; Benmounah, A.; Hamiane, Messaoud
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