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This paper aims at developing a probabilistic model of unidirectional composite with random fiber spacing, in order to predict the stress concentration at the broken and neighboring fibers. Micromechanical technique with random fiber spacing is used in the development of a new formulation of load sharing between broken and nearest neighbors fibers....
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... equilibrium of forces between fibers i and j can therefore be written: The system of Eq. (11) cannot be solved analytically, as done for the special case of deterministic analysis done in [5]. For this reason, the finite difference technique is applied on discretized segments on the fiber length, as illustrated in Fig. 4 ...
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In this paper, hole stress concentrations in long fibers and their surrounding matrix bays is examined in a hybrid composite lamina. It is assumed that all fibers lie in one direction while loaded by a force p at infinity in the direction of fibers. The width of the lamina is considered to be finite and bears a hole as a defect. Due to the presence...
In this paper, hole stress concentrations in long fibers and their surrounding matrix bays is examined in a hybrid composite lamina. It is assumed that all fibers lie in one direction while loaded by a force p at infinity in the direction of fibers. The width of the lamina is considered to be finite and bears a hole as a defect. Due to the presence...
Citations
... From some of the work presented above (Hamamousse et al., 2019, Berrekheroukh et al., 2022Amrane et al., 2019) and literature (Bouhamida et al., 2013;Wang et al., 2022;Benzidane et al., 2022), the mechanical properties of the specimens seem to represent an important dispersion of the results. As these results are highly variable, they require uncertainty studies or analysis. ...
In the present paper, the effect of the fiber contents and the curvature on the probabilistic analysis of free vibration
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... A probabilistic model has been developed by Khiat et al. (2011) to study the strength of unidirectional composites with fibers in hexagonal arrays and developed a modified shear lag model to predict the ineffective lengths in intact fibers and stress concentrations around fiber breaks. Bouhamida et al. (2013Bouhamida et al. ( , 2016) developed a 3D finite difference scheme to predict the stress concentration at the broken and neighboring fibers. Using the Monte Carlo method, a probabilistic model is developed to study the sensitivity of the mechanical response according to mechanical and geometrical properties of fibers and matrix. ...
In this paper, we propose an experimental and numerical model to study the creep behavior of the unidirectional Alfa fiber composite strength by the photoelasticity method. To have better mechanical properties, chemical treatment is made for Alfa fibers. Tensile tests are made to predict the Young modulus and tensile strength. These tests confirm that the chemical treatment during 48 Hours of Alfa fibers collected from the south region gives the best results. After that, specimens are made in Medapoxy STR resin and treated Alfa fibers of the south region. All fibers of specimens are arranged approximately in multiple hexagonal clusters embedded in the matrix. For the micromechanical fiber stress redistribution or load sharing theory to be applied, clusters must minimally contain one broken fiber. Consequently, we have a stress perturbation due to a fiber fracture, which propagates to the nearest-neighbor fibers. This perturbation enables us the photoelastic visualization of the fracture events during the creep tests. The contour diagram and fringe values give us the accurate distribution of stress near broken fibers showing local shear stress concentrations during the time. To simulate the creep response and failure mechanism, the Tsai–Wu failure criterion was applied on ANSYS explicit dynamic software. Because it merges between experimental tests and numerical simulation, the present study offers a real scientific contribution in the creep behavior of biobased composite strength by the photoelasticity method.
... The broken fiber concentration distribution happens according to two main criteria. These are the distance that separates the broken fiber from the around ones and the fiber diameter Bouhamida et al. [16]. Fig. 11 shows both distributions on the intact fibers. ...
During the fiber fracture of unidirectional composite a distribution of stress around the neighbored fibers happens, this mechanism is called the local redistribution efforts. Referring to the "shear lag" method, the researches wanted to predict the stress concentration in the surrounding area of broken fibers as well as the longitudinal resistance of the unidirectional composite which presents a fiber breaking. The goal of this paper is to develop a new probabilistic model of unidirectional composite plate to calculate the stress concentration at the broken fibers and their neighboring fiber intact. The "shear lag" method has been generalized to see the broken fibers interference on the stress concentration factor variation of surrounding sound fibers.
... As a result, an elastic overlapped region between the whiskers is essential to attain the driving force required for the recrystallization and prevention of the ductility deterioration [19]. According to the Monte-Carlo model, the stress concentration region around a whisker is dependent on l and the radius of the closest whisker [23]. Considering the stress concentration at whiskers' tips, the upper bound of l is determined by Eq. (3) [24]. ...
In this study, high-temperature tensile properties and microstructure of ZK60/SiCw composite were investigated in “as-cast” and “extruded + precipitation-hardened” conditions. Stir casting followed by extrusion and aging at 175 °C for 12 h was employed to prepare the composite samples containing 5 vol% SiC whiskers. Aligned whiskers and the severely deformed matrix resulted in a quasi-continuous network structure of the reinforcement and laminar structure of the matrix. Tensile tests, conducted in the temperature range of 25–350 °C, revealed that the anisotropic structure led to an improvement in the ductility and strength. The elastic modulus of the composite was dependent on the alignment and distribution of the reinforcement. While the elastic modulus in the extrusion direction was close to the upper bound of the Halpin–Tsai (H-T) model at temperatures below 250 °C, it approached to the lower bound of the model at temperatures above 300 °C. Moreover, 0.2% proof stress, ultimate tensile strength and elastic modulus decreased nonlinearly with temperature. Examination of the fracture surfaces revealed the fracture of whiskers with slight pull-out due to the strong whisker/matrix interface.
... It uses random variables to establish a simple but effective statistical model according to the statistical law of practical problems. For instance, Bouhamida et al. combined MCS to study the distribution of stress concentration for each fiber [28]. Campanile et al. applied MCS with Weibull distribution to investigate statistical properties of the hull girder section modulus and ultimate strength [29]. ...
The fatigue resistance of coarse-grained (CG) metals can be greatly improved by introducing a nanograined surface layer. In this study, the Weibull distribution is used to characterize the spatially-random fracture properties of specimens under axial fatigue. For the cylindrical solid specimen, the heterogeneity of element sizes may lead to unfavorable size effects in fatigue damage initiation and evolution process. To alleviate the size effects, a three-dimensional cohesive finite element method combined with a local Monte Carlo simulation is proposed to analyze fatigue damage evolution of solid metallic specimens. The numerical results for the fatigue life and end displacement of CG specimens are consistent with the experimental data. It is shown that for the specimens after surface mechanical attrition treatment, damage initiates from the subsurface and then extends to the exterior surface, yielding an improvement in the fatigue life. Good agreement is found between the numerical results for the fatigue life of the specimens with the nanograined layer and experimental data, demonstrating the efficacy and accuracy of the proposed method.
... It uses random variables to establish a simple but effective statistical model according to the statistical law of practical problems. For instance, Bouhamida et al. combined MCS to study the distribution of stress concentration for each fiber [28]. Campanile et al. applied MCS with Weibull distribution to investigate statistical properties of the hull girder section modulus and ultimate strength [29]. ...
... It uses random variables to establish a simple but effective statistical model according to the statistical law of practical problems. For instance, Bouhamida et al. combined MCS to study the distribution of stress concentration for each fiber [28]. Campanile et al. applied MCS with Weibull distribution to investigate statistical properties of the hull girder section modulus and ultimate strength [29]. ...
... It uses random variables to establish a simple but effective statistical model according to the statistical law of practical problems. For instance, Bouhamida et al. combined MCS to study the distribution of stress concentration for each fiber [28]. Campanile et al. applied MCS with Weibull distribution to investigate statistical properties of the hull girder section modulus and ultimate strength [29]. ...
The fatigue resistance of coarse-grained (CG) metals can be greatly improved by introducing a nanograined surface layer. In this study, the Weibull distribution is used to characterize the spatially-random fracture properties of specimens under axial fatigue. For the cylindrical solid specimen, the heterogeneity of element sizes may lead to unfavorable size effects in fatigue damage initiation and evolution process. To alleviate the size effects, a three-dimensional cohesive finite element method combined with a local Monte Carlo simulation is proposed to analyze fatigue damage evolution of solid metallic specimens. The numerical results for the fatigue life and end displacement of CG specimens are consistent with the experimental data. It is shown that for the specimens after surface mechanical attrition treatment, damage initiates from the subsurface and then extends to the exterior surface, yielding an improvement in the fatigue life. Good agreement is found between the numerical results for the fatigue life of the specimens with the nanograined layer and experimental data, demonstrating the efficacy and accuracy of the proposed method.
... Le modèle mathématique est détaillé dans l'article (Bouhamida et al., 2013). En se servant de l'hypothèse de shear-lag, les forces d'influences sont estimées à partir des déplacements des fibres, qu'on peut écrire : ...
... Illustration du modèle hexagonal à trois dimensions avec l'espacement aléatoire(Bouhamida et al., 2013) En outre, X ∆ (= x ∆ / ξ ) est la petite longueur de la fibre, et les autres limites de déplacement correspondent à la rupture des fibres et de la matrice à proximité de la fibre cassée au point(i, j, k). Les conditions aux limites de type Dirichlet sont appliquées, conformément au modèle sheard'influence de forces q i,k peuvent être évaluées par les équations suivantes :, ...
The present work aims at developing an analytical model of shear-lag of a cell of unidirectional composites made from natural fibers (Alfa) with irregular spacing between fibers. The finite difference method is used to calculate the "Stress Concentration Factor" (SCF) at the neighboring fibers. By the development of a pattern of three-dimensional finite differences with random spacing between fibers, a coupled system of equations is obtained for the displacement and stress concentration in the fibers. By varying the distance between the fibers and their diameters, the sensitivity distribution of the SCF is evaluated along the fibers. A probabilistic analysis of a cell of a unidirectional composite having a break in the central fiber is then conducted to evaluate the effect of geometrical and mechanical uncertainties on the evolution of the stress concentration. The probabilistic study is performed using Monte Carlo simulations to assess the sensitivity of the model with respect to geometrical and mechanical uncertainties.
In this present work, a non-straight Shear-lag model has been created to anticipate the pressure centralization of a customary hexagonal cell containing a two-bundled fiber. This work is concretized by the advancement of a hypothetical plan of the micromechanical redistribution of the anxieties produced by the transverse burst along the strands in a unidirectional composite as an element of the number and the air of the messed up and flawless filaments. The scientific improvements utilized are introduced to legitimize the state of the conveyance of the worries around the messed up fiber and the adjoining filaments. The limit and coherence conditions are considered by this model to evaluate the exchange pace of the strands, imperatives through the lattice between the fiber broken and the neighboring filaments unblemished.
