Publications Scientifiques

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Author: search.filters.author.Madani, Kouider

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    Numerical analysis reveals cold expansion's influence on rivet hole stress and j-integral values
    (Editura Politechnica, 2024) Abdelkader, Djelti; Mohamed, Elajrami; Nadia, Kaddouri; Houari, Amin; Amroune, Salah; Madani, Kouider
    In the aeronautical construction several rivet holes are drilled, these holes constitute stress concentration zones which can be affects the fatigue life through cracks initiation at the edge of rivet holes. To remedy this problem and minimize stress level in these zones, the cold expansion technique is used to enhancing the fatigue life of rivet holes. The present work aims to investigate through finite element analysis the effect of three degree cold expansion (2%, 4.5% and 6%) on the reduction of stress level on the edge of rivet hole. The hole-crack interaction effect was thus analyzed. This effect is quantified by the values of J-Integral at the two tip of crack. The obtained results show that negative values of J- Integral was found which can be explained by the beneficial effect of residual compressive stresses induced by cold expansion on the crack closing.
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    Prediction of mass adhesive damage based on the Rousselier model: Experimental and numerical analysis
    (Elsevier Ltd, 2024) Houari, Amin; Madani, Kouider; Belhouari, Mohamed; Amroune, Salah; Cohendoz, Stéphane; Preaudeau, Bruno; Feaugas, Xavier; Campilho, Raul DSG.
    The study of the mechanical strength of adhesives remains an important area of research for researchers. These adhesives must be prepared in the form of mass test pieces to characterize them under different mechanical stresses. However, during the preparation of the test pieces several defects are likely to be present, namely air bubbles, cavities, or impurities. The behavior of the adhesive differs depending on the presence of one of these defects and, in most cases, the real behavior of the adhesive is not precisely known. For this purpose, several tests are necessary to have a close estimate of the adhesive's behavior. To numerically model the behavior of the adhesive it is necessary to consider the presence of these types of defects. This paper proposes a damage criterion based on the Rousselier model, which describes the damage due to crack growth from the presence of cavities in an adhesive, assumed as a ductile material. The proposed damage model was developed and implemented in a user-defined subroutine in the ABAQUS finite element code. Other damage models integrated into ABAQUS were used. In addition, the extended finite element method (XFEM) was used in the numerical simulations to study automatic damage modelling by the appearance and propagation of cracks in highly stressed areas. The main objective of this work is an analysis by the finite element method to determine the elastoplastic behavior coupled with the damage in the mass adhesive, considering the size, position, and shape of the defect (porosities) by the proposed models. Initially, experimental tests were carried out on mass specimens of adhesive to characterize the tensile response and to determine their mechanical properties depending on the position and size of the defect, which may exist in the specimen following its fabrication. The numerical results were validated by uniaxial tensile tests on the mass adhesive. Comparisons with the damage models integrated into ABAQUS have proven their effectiveness in predicting the behavior of the adhesive in the presence of a cavity.
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    Experimental Investigation Into the Tensile Strength Post-Repair on Damaged Aluminium 2024 -T3 Plates Using Hybrid Bonding/Riveting
    (Sciendo, 2024) Merah, Abdelkrim; Houari, Amin; Madani, Kouider; Belhouari, Mohamed; Amroune, Salah; Chellil, Ahmed; Yahia, Cherif Zineelabidine; Campilho, Raul D.S.G. Duarte Salgueiral Gomes
    Since the implementation of repair processes by composite patch bonding, this process has consistently demonstrated high performance across various industrial sectors, especially in the fields of aeronautics, aerospace and civil engineering. Consequently, there are situations in which the riveting process becomes the sole solution, particularly when the structure is subjected to severe mechanical or thermo-mechanical stresses, since adhesives have low mechanical strength after aging. Each method has its own set of advantages and disadvantages. The current trend is to combine these two processes to minimise their drawbacks as much as possible. The objective of this work is to present an experimental study on the repair of an aluminium plate AL2024-T3 with a central circular notch using a patch of different nature (metal or composite), under tensile loading conditions. The repair composite considered is a carbon/epoxide. The results of the tensile tests showed that the repair by the combination of the two processes improves the mechanical strength of the damaged structure. A comparison of the results of the experimental curves obtained on riveted, bonded and hybrid assemblies has been taken into consideration.
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    Predicting damage in notched functionally graded materials plates through extended finite element method based on computational simulations
    (Gruppo Italiano Frattura, 2024) Siguerdjidjene, Hakim; Houari, Amin; Madani, Kouider; Amroune, Salah; Mokhtari, Mohamed; Mohamad, Barhm; Ahmed, Chellil; Merah, Abdelkrim; Campilho, Raul D.S.G. Duarte Salgueiral Gomes
    Presently, Functionally Graded Materials (FGMs) are extensively utilised in several industrial sectors, and the modelling of their mechanical behaviour is consistently advancing. Most studies investigate the impact of layers on the mechanical characteristics, resulting in a discontinuity in the material. In the present study, the extended Finite Element Method (XFEM) technique is used to analyse the damage in a Metal/Ceramic plate (FGM-Al/SiC) with a circular central notch. The plate is subjected to a uniaxial tensile force. The maximum stress criterion was employed for fracture initiation and the energy criterion for its propagation and evolution. The FGM (Al/SiC) structure is graded based on its thickness using a modified power law. The plastic characteristics of the structure were estimated using the Tamura-Tomota-Ozawa (TTO) model in a user-defined field variables (USDFLD) subroutine. Validation of the numerical model in the form of a stress-strain curve with the findings of the experimental tests was established following a mesh sensitivity investigation and demonstrated good convergence. The influence of the notch dimensions and gradation exponent on the structural response and damage development was also explored. Additionally, force-displacement curves were employed to display the data, highlighting the fracture propagation pattern within the FGM structure.
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    Experimental investigation into the tensile strength post-repair on damaged Aluminium 2024 -T3 plate using hybrid bonding/riveting
    (2024) Merah, Abdelkrim; Houari, Amine; Madani, Kouider; Belhouari, Mohamed; Amroune, Salah; Chellil, Ahmed; Yahi, Cherif Zineelabidine; R.D.S.G., Campilho
    Since the implementation of repair processes by composite patch bonding, this process has consistently demonstrated high performance across various industrial sectors, especially in the fields of aeronautics, aerospace and civil engineering. Consequently, there are situations in which the riveting process becomes the sole solution, particularly when the structure is subjected to severe mechanical or thermo-mechanical stresses, since adhesives have low mechanical strength after aging. Each method has its own set of advantages and disadvantages. The current trend is to combine these two processes to minimize their drawbacks as much as possible. The objective of this work is to present an experimental study into the repair of an aluminum plate AL2024-T3 with a central circular notch using a patch of different nature (metal or composite), under tensile loading conditions. The repair composite considered is a carbon/epoxide. The results of the tensile tests clearly showed that the repair by the combination of the two processes clearly improves the mechanical strength of the damaged structure. A comparison of the results of the experimental curves obtained on riveted, bonded, and hybrid assemblies has been taken into consideration.
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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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    Experimental and numerical study of the effect of the presence of a geometric discontinuity of variable shape on the tensile strength of an epoxy polymer
    (Sciendo, 2023) Saada, Khalissa; Amroune, Salah; Zaoui, Moussa; Houari, Amin; Madani, Kouider; Hachaichi, Amina
    The presence of geometric discontinuity in a material reduces considerably its resistance to mechanical stresses, therefore reducing the service life of materials. The analysis of structural behaviour in the presence of geometric discontinuities is important to ensure the proper use, especially if it is regarding a material of weak mechanical properties such as a polymer. The objective of the present work is to analyse the effect of the notch presence of variable geometric shapes on the tensile strength of epoxy-type polymer specimens. A series of tensile tests were carried out on standardised specimens, taking into account the presence or absence of a notch. Each series of tests contains five specimens. Two notch shapes were considered: circular (hole) and elliptical. The experimental results in terms of stress-strain clearly show that the presence of notches reduces considerably the resistance of the material, where the maximum stress for the undamaged specimen was 41.22 MPa and the lowest stress for the elliptical-notched specimen was 11.21 MPa. A numerical analysis by the extended finite element method (XFEM) was undertaken on the same geometric models; in addition, the results in stress-strain form were validated with the experimental results. A remarkable improvement was obtained (generally an error within 0.06%) for strain, maximum stress, Young's modulus and elongation values. An exponential decrease was noted in the stress, strain, and Young's modulus in the presence of a notch in the material