Browsing by Author "Grabi, Massinissa"

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Alkaline Treatment’s Effect on Mechanical Properties and Damage Assessment Through Acoustic Emission of Luffa Fiber Composite
(Springer, 2022) Grabi, Massinissa; Chellil, Ahmed; Habibi, Mohamed; Laperriere, Luc
Improving the mechanical properties and reduced damage of natural fiber-reinforced composites can contribute to their increased use in various fields. In this paper, an experimental study describes the effect of alkaline treatment of two different concentrations of 2 % and 5 % NaOH for one hour on the mechanical performance and damage of luffa fiber composites. Three different composites reinforced with treated and untreated luffa fibers were developed using the resin transfer molding (RTM) process. The specimens were coupled with acoustic emission during tensile tests, to monitor and evaluate damage mechanisms. The tensile test results showed that the alkaline treatment of 5 % improved tensile strength, which reached 81.08±1.48 MPa. However, the 2 % treatment improved Young’s modulus with 8.94±0.5 GPa. In comparison, T2 % and T5 % composites provided the best results for mechanical properties compared to NT composites. Four classes of damage mechanisms have been identified using the K-means clustering method, including matrix cracking, fiber pull-out, delamination, and fiber breakage. The cumulated energy and hits of the 5 % treated composite was lower than the untreated and 2 % treated, which means less damage to the T5 % specimen. Scanning electron microscopy (SEM) pictures of the tensile fractured surfaces of luffa fiber composites treated with 5 % NaOH, revealed good adhesion between the fibers and the matrix. The AE results are convincing, and they were confirmed by SEM pictures of the specimens’ fractured faces, which revealed the main causes of material failure, So, based on the AE results and mechanical properties, T5 % composite is preferable.
Characterization of low-velocity impact and post-impact damage of luffa mat composite using acoustic emission and digital image correlation
(SAGE Publications, 2022) Grabi, Massinissa; Chellil, Ahmed; Habibi, Mohamed; Grabi, Hocine; Laperriere, Luc
In this paper, low-velocity impact and compression after impact damage tolerance of composite reinforced with natural luffa mat were studied for the first time. The effect of impact energy and the influence of the damaged area on the residual mechanical properties under compression were investigated. Acoustic emission (AE), digital image correlation (DIC) and scanning electron microscopy (SEM) were used for the evolution of different damage modes and displacement fields. The findings of the experiments reveal that compression after impact tests of 1, 2, and 3J show a significant effect of the residual damage which decreases residual compressive strength by 12.61, 24.14, and 30.9%, respectively, compared to the unimpacted composite, but Young’s modulus was not significantly affected. Multivariable statistical analysis of the AE signals identified four classes of damage: matrix cracking, fiber-matrix debonding, delamination, and fiber failure. It also showed that the damage mode of unimpacted composites which presents the majority of the amplitude events of the AE signals is mainly due to fiber failure, by contrast, for impacted composites the damage mode is mainly due to fiber-matrix debonding. The AE results are convincing and they were confirmed by SEM images of the fractured faces of the specimens, which revealed the main causes of material failure during the compression after impact test. The DIC system monitored the effect of pre-existing damage under compressive loading and found that increasing impact energy increases the stress concentration around the impacted area and has a significant effect on residual crack development, much more in the loading direction
Comportement à l'impact et post impact des matériaux composites renforcées par les fibres de luffa
(Université M'Hamed Bougara : Faculté de Technologie, 2022) Grabi, Massinissa; Chellil, Ahmed(Directeur de thèse)
Cette étude porte sur le comportement à l’impact et post-impact d’un composite à fibre de luffa et à matrice époxy. La première partie a été consacrée sur l'effet de traitement alcalin (2% et 5% de NaOH) sur les propriétés mécaniques et les endommagements. Pendant les essais de traction, les tests ont été couplés à l'émission acoustique (EA) et corrélation d'images numériques (CIN), afin de surveiller et d'évaluer les mécanismes d'endommagements et les champs des déformations. Sur la base des résultats EA, CIN et les propriétés mécaniques, le composite T5% est le plus performant. Des essais d’impact à basse vitesse ont été réalisés sur quatre composites nommés (A), (B), (C), et (D). Les résultats montrent que le composite (C) est le plus résistant au impact suivi par le composite (A), par contre le composite (D) est le plus absorbant d’énergie suivi par le composite (B). Par la suite des essais d’indentations ont été réalisés et des techniques d’analyses ont été menées sur des éprouvettes qui sont couplé aussi aux techniques de caractérisation par émission acoustique et la corrélation d’image numérique. Les résultats d’EA identifier quatre modes d’endommagement, y a compris la fissuration de la matrice, décohésion fibre-matrice, délaminage, et la rupture des fibres. La dernière partie de ce travail a été consacrée sur la compression après impact (CAI). L'effet de l'énergie d'impact et l'influence de la zone endommagée sur les propriétés mécaniques résiduelles sous compression ont été déterminé. L'émission acoustique (EA), la corrélation d'images numériques (CIN) et la microscopie électronique à balayage (MEB) ont été utilisées,pour l'évolution des différents modes de dommages et des champs de déplacements. Les résultats révèlent que les CAI 1J, CAI 2J et CAI 3J montrent un effet de l'endommagement résiduel diminue la résistance résiduelle à la compression, par rapport au composite non impacté, par contre le module de Young n'est pas affecté de manière significative. L'analyse des signaux EA a permis d'identifier quatre classes de dommages, elle a également montré que le mode d'endommagement des composites non impactés, qui présente la majorité des événements d'amplitude des signaux EA, est principalement dû à la rupture des fibres, alors que pour les composites impactés, est principalement dû au décohésion fibre-matrice. La technique CIN a constaté que l'augmentation de l'énergie d'impact augmente la concentration de contraintes autour de la zone impactée.
Identification of vibratory characteristics to the damage of a composite plate
(2018) Grabi, Massinissa; Chellil, A.; Lecheb, Samir; Mechakra, H.; Nour, A.; Andrianarison, O.
tThe objective of this work is to study the damage behavior of composite structures by examining the influence on fatigue resistance. The finite element model of the plate will allow to analyze the vibratory behavior, to identify the stress, to study the influence of the dynamic loads on the natural frequencies of the plate in bending and torsion and will show the influence of the orientation of the Composite fiber macros on the rigidity of the plate and finally calculate the stability of the plate. The various damage mechanisms associated with these materials will also be presented with particular attention to delamination and cracking. This work will then focus on different technologies to improve the mechanical properties of these composite materials.
Impact Behavior Analysis of Luffa/Epoxy Composites Under Low-Velocity Loading
(Springer Nature, 2024) Grabi, Massinissa; Chellil, Ahmed; Lecheb, Samir; Grabi, Hocine; Nour, Abdelkader
Luffa cylindrical (LC) has an exceptionally multipartite architecture, a hierarchical and light structure, and a low density. Such a structure is potentially suitable to replace conventional porous-type composites for low-energy absorption and material reinforcement applications. This paper presents an experimental study of the impact behavior of four different luffa/epoxy composites, named (A), (B), (C), and (D) subjected to low-velocity impact (LVI) at energies ranging from barely visible impact damage (BVID) to perforation (5,15, and 20J). Acoustic emission (AE), scanning electron microscopy (SEM), and digital image correlation (DIC) were introduced to the indentation test to offer additional information on damage mechanisms and on strain and displacement fields since the LVI test has a short duration and real-time damage monitoring is not always achievable. The results showed that the values of the peak force of laminates (A), (B), and (D) are relatively lower compared to laminates (C). In the case of perforation impact energy (20J), the Coefficients of Restitution (CoR) of composites (A), (B), and (D) are equal to 0, which indicates that the nature of the impact is completely plastic, except for composite (C) had a value of 0.11, and a lower degree of damage at all impact energies. Composites (C) exhibit the highest impact resistance, followed by composites (A), while composites (D) display the highest energy absorption, followed by composites (B). Multivariable statistical analysis of the AE signals identified four classes of damage: matrix cracking, fiber-matrix debonding, delamination, and fiber breakage. The damage modes found by AE are well presented and proven by SEM analysis. The luffa fiber-reinforced composite has better impact properties than other natural fiber-reinforced composites.
Strain and Damage Assessment of Treated and Untreated Luffa Mat Composite Using Acoustic Emission and Digital Image Correlation
(Taylor et francis, 2022) Grabi, Massinissa; Chellil, Ahmed; Habibi, Mohamed; Laperriere, Luc; Grabi, Hocine
In this work, acoustic emission and digital image correlation were applied to three different composites reinforced with treated (2% and 5% NaOH) and untreated luffa fibers during tensile testing, to follow the evolution of the different damage modes and determine strains and Poisson’s ratio. The tensile test results showed that alkaline treatment of 5% improved Young’s modulus and tensile strength. In comparison, the 2% treatment showed the most outstanding improvements in mechanical properties. The K-means clustering methodology identified four types of damage: matrix cracking, fiber pull-out, delamination, and fiber breaking. The 5% treated composite had lower cumulative energy and hits than the untreated and 2% treated composites, implying that the T5% composite suffered less damage. The DIC results showed that the longitudinal strains found by the extensometer are very approximate to those found by DIC, this technique also allows us to find the transverse strains of the composites UT (0.324), T2% (0.295), and T5% (0.207%). It is shown that the 5% alkaline treatment leads to the decrease of Poisson’s ratio (0.2378) compared to 2% treated (0.3113) and untreated (0.3120) composites. Based on AE, DIC results, and mechanical properties, the T5% composite is the most successful.