International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 7, July – 2018, Pages: 1-5 www.ijeais.org/ijaer 1 Tensile Properties Prediction of Natural Fibers Metal Laminates FMLs 1 Hicham Laribou, 2 Abdelali El-Bakari 1Laboratoire de Microstructure et de Mécanique des Matériaux Université de Lorraine Metz-France Hicham.laribou@laposte.net 2Laboratoire de Mécanique et génie civil Université Abdelmalek Essaadi Tanger-Maroc ab_elbekari@yahoo.fr Abstract: Fiber–metal laminates (FMLs) are high-performance hybrid structures based on alternating stacked arrangements of fiber-reinforced plastic (FRP) plies and metal alloy layers FMLs have benefits over both aluminum and fiber reinforced composites. In this work, a jute fibers and effect of fiberFE volume fraction on tensile behavior of this novel material is investigated. A numerical simulation method based on finite element modeling (FEM) is used to predict the tensile proprerties of FMLs and compared with a result obtained by a modified classical laminate theory (CLT) given in literature. Good agreement is obtained between the models predictions and mathematical results. The obtained results show that the fiber volume fraction improves elastic and plastic moduli, yield stress and ultimate tensile stress considerably. Statistical analysis of data is done and an estimated tensile strength of each FMLs as a function of fiber volume fraction is obtained Keywords-Fiber metal laminates, Finite element analysis, yield strength prediction 1. INTRODUCTION The Fiber Metal Laminates (FMLs) are a family of hybrid metallic–polymer matrix composite materials made from multi thin layered materials based on the stacked arrangement of Aluminum alloys sheets and fibers embedded in adhesive i.e. rubber toughened epoxy. The variant with glass fibers is called Glare and his first commercial use was in 1987. The laminated layout creates a material with high strength, excellent rigidity, insulation proprieties and great lightness [1]. Fig. 1.Typical Fiber Metal Laminate lay-up [1] The prospect of a possible 20% weight reducing for aircraft structures was the prime driver behind the Glare development. Indeed, Krishnakumar et al [2] have deduced that the tensile strength of many FMLs is better than different aerospace alloys with an advantage of weight reduction. The conventional design principles and methods available for aluminum were taken as a starting point, and were adapted for the specific features of Glare such as anisotropy and elastic fibre layers. This ensured a better acceptance of these methods and principles by the aircraft industry. Many methods for Glare already existed, because they were part of the material development that was carried out in Delft by MScand PhD-students during the last fifteen years. It had to be proven that these structural analysis methods were accurate and reliable for industrial application as well [1]. Moreover, Luciano et al [3] presented analytical form relations for determining proprieties of composite lamina from the proprieties of constituent. Otherwise, Hagenbeek et al [4] presented also an analytical procedure for the calculation of uniaxial stress-strain behaviour of Glare. Wu et al [5] presented an analytical modelling and numerical simulation of the tensile proprieties of hybrid FMLs. Furthermore, Mourssavi-Torshizi et al [6] studied the tensile proprieties of novel FMLs experimentally, analytically and trough finite element method by the use of the modified Classical Laminate Theory (CLT) to obtain the stress-strain behaviour of developed FMLs analytically. In this paper, we will proceed by the use of the finite element method to modelling a Fiber Metal Laminates, based on the aluminum alloy A5086 and epoxy reinforced with jute fiber in ANSYS. A good agreement will be obtained between the model predictions and experimental results. Then the validation of the modelling approach will be approved by an analytical model available in the literature [6]. Finally, we will study the effect of jute fiber volume fraction on the tensile properties of the FLMs obtained. International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 7, July – 2018, Pages: 1-5 www.ijeais.org/ijaer 2 2. MATERIALS AND METHODS 2.1 Materials The aluminum alloy AA5086 is the most common type metal used for setting up a FMLs for their low density and their high mechanical properties. In the present work the aluminum alloy AA5086 with bilinear elasto-plastic behaviour has been used as the metal part in the FMLs, and its chemical composition and some mechanical characteristics are given by Tables 1and 2. Table 1: Chemical composition of the aluminum alloy AA5086 Al Fe Ti Mg Mn Si Zn Cu Cr 95,2  0,36  0,02  3,83  0,23  0,17  0,01  0,01  0,15  Table 2: Some mechanical characteristic of the aluminum alloy AA5086 [6] Elastic young's modulus Eel Tangent modulu Epl Yield strength Syt 46,5GPa 770 MPa 275 MPa Recently environmental standards are becoming more and more severe. These regulations have led to the emergence of a promising alternative that consists in developing biocomposite materials developed with ecofriendly reinforcements from renewable natural resources. Vegetable fibers seem to be the best candidates, hence the choice in this study to use a jute fibers which offer a high strength with a low cost. Tables 3 and 4 give a chemical composition and mechanical properties for the jute fibers. Table 3: Chemical composition of jute fibers [7] Cellulose Hemicellulose Lignin Ash Wax Moisture 61-71% 13,6-20,6% 12-13% 0,5-2% 0,5% 12,6% Table 4: Mechanical properties of jute fibers [8] Property Tensile strength (MPa) Modulus of Elasticity (GPa) Elongation at break (%) Density (g/ cm 3 ) Value 410-780 26.5 1.9 1.48 As the matrix material we used an epoxy resins in the present study, which offers a high tensile strength, high rigidity, chemical resistance, fire resistance and low curing shrinkage. Its application fields are widespread and remain very useful [9] [10]. 2.2 Calculation methods Most commercial FEM codes provide 2D elements suitable for stress analysis of composite and sandwich structure. In our current case, three general pathways (micro, meso and macro-scale) of modelling FMLs have been outlined by [7], and the dimensions of finite element model were chosen to be 175mm x 25mm x 1mm based on the recommendations of [6]. Fig 2.Finite element model: (a) meshing; (b) boundary conditions In this study the FMLs were modeled by commercially available FEM software, ANSYS 11 with SHELL 91 element. SHELL 91 is a nonlinear layered structural shell element. The element is defined by eight nodes nonlinear element used to discrete the domain of our ANSYS product. Tensile load is applied on the vertical sides of the finite element model in 20 substeps to capture the non-linear behaviour of the FMLs (Figure 2). The bilinear elasto-plastic behaviour of the AA 5086 layer is incorporated using the Von-Mises plasticity option in ANSYS. Also, a numerical simulation, based on finite element modelling is employed to predict the stress–strain response of FMLs. Micromechanics relates the elastic properties of the lamina with the individual properties of fiber and matrix and their volume fraction C∗=(Cf, Cm, Vf) with, C∗ is elasticity of matrix, Cf is elasticity of fiber, Cm is elasticity of metal and Vf is a fiber volume fraction. [Luciano and Barbero, 1994] presented an analytical closed form solution of for doing so without the need of experimentation by using periodic microstructure approach. As for the basic material properties, the metal volume fraction approach was proven to be valid for shear stiffness and blunt notch and yield strength. International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 7, July – 2018, Pages: 1-5 www.ijeais.org/ijaer 3 Fig 3.Schematic illustration of Stress-Strain curves The mathematical model as provided by [6] has been used in the present investigation to validate the results of FEM. It can be observed from Figure 3 that, stress–strain curve of FML is separated into two parts. In the first part both aluminum and fiber reinforced plastic (FRP) layers like glass/epoxy and Kevlar/epoxy The mathematical model is a modification of the Classical Laminate Theory (CLT) to consider the elasto-plastic behaviour of the FML. MATLAB codes were written to implement the mathematical model and obtain the results. For a linear-elastic material behaviour [12]: When σFML is total stress in laminate, (σy) is yield stress of laminate, EFML is the young's modulus of the laminate, EAl is the young's modulus of aluminum layer and (σy)AL is yield stress of aluminum layer. The equation can be derived as: Where tAl is the total thickness of aluminum layers, tFRP is the total thickness of fibrous layers consist of one Kevlar/epoxy layer and two glass/epoxy layers. The thickness of each Glass/epoxy layer was about 0.35 mm and thickness of Kevlar/epoxy layer was about 0.3 mm. tFML is the total thickness of all layers, and εFML is total strain of laminate. EFRP is the Young's modulus of the fibrous Layer which was calculated using classical laminate theory. In the second part aluminum becomes plastic. For elastic–plastic laminate: Where (εel)AL is elastic strain of aluminum layer. The modulus of elasticity in this part is calculated in the same way as the first part but with (Epl)AL instead of (Eel)AL. Where (Epl)AL is tangent modules of aluminum stress– strain curve in plastic region, and ÊFML is tangent modules of FML stress–strain curve in plastic region. Now the overall stress-strain behaviour of the FML can be estimated from. (3) and (6). The designation of laminates with fiber volume fraction matrix and volume fraction designation is given by Table.5. Table 5: Designation of FMLs Fiber volume fraction Matrix volume fraction Designation 0.2 0.8 Al/JRE(0.2)/Al/JRE(0.2)/Al 0.4 0.6 Al/JRE(0.4)/Al/JRE(0.4)/Al 0.6 0.4 Al/JRE(0.6)/Al/JRE(0.6)/Al 0.8 0.2 Al/JRE(0.8)/Al/JRE(0.8)/Al 3. RESULTS The exploitation of all the data previously obtained has allowed to getting the stress–strain curves for each FMLs given in Table 5 by using a Finite Element Analysis (FEA) and analytically computation. The set of stress strain behavior curves obtained are shown in Figure 4. (a). Al/JRE (0.2)/Al/JRE (0.2)/Al (b). Al/JRE (0.4)/Al/JRE (0.4)/Al International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 7, July – 2018, Pages: 1-5 www.ijeais.org/ijaer 4 (c). Al/JRE (0.6)/Al/JRE (0.6)/Al (d). Al/JRE (0.8)/Al/JRE (0.8)/Al Fig 4.Tensile stress-strain behaviour for different FMLs By analyzing these different obtained curves, we have managed to correlate a variation of tensile strength as a function of fiber volume fraction. As shown in Figue 5, both outputs of mathematical and the finite element model are plotted for the two calculation methods (FEA and analytically one) the FMLs tensile strength constantly increases as the fiber fraction volume grow Fig 5.Variation of tensile strength with fiber fraction volume The stress–strain curves that are obtained with analytical prediction curves and FEM prediction results; it is clear that analytical calculations and finite element modeling results are in good agreement; the final remarks remain the same. And a good correlation is obtained comparing with the last model. Furthermore, Figure 6 shows also that the elastic and plastic moduli grow with fiber fraction volume with close value for FEA and analytically method. Fig 6.Variation of elastic and plastic moduli with fiber volume fraction From the results it can be concluded that the fiber volume fraction orientation in laminate improve modulus of elasticity, yield stress and ultimate tensile stress considerably Hence, the final goal of this study consists of holding out the tensile strength behaviour. This reflects the ability of this model to provide a powerful tool as a tensile strength behaviour prediction. This new approach based on the statistical analysis of the results, following linear regression equations are proposed for predicting different parameters: For elastic modulus of FML: Eel = 9242.5Vf + 29263 For plastic modulus of FML: Epl = 9439.1Vf + 1768.7 For tensile yield strength of FML: Syt = 55.04Vf + 172.9 4. USING THE TEMPLATE The effects of fiber volume fraction on tensile properties of fiber/metal laminates are simulated. The performed numerical study in this paper is to predict the tensile properties such. elastic and plastic moduli and yield strength of new aluminum and Jute fibers based FMLs using Finite Element Method. In this approach, elastic–plastic behavior of the aluminum sheets was modeled by a bilinear relation and fiber reinforced plastic layers was assumed to be linear elastic up to fracture. The results of the Finite Element Method are validated using already published mathematical model. REFERENCES [1] Gunnink J., W., Vlot A., Alderliesten R., C., van der Hoeven W., de Boer A., Hart W., t., van Hengel C., G., Kuijpers P., L., van Oost R., C., Roebroeks G., H., J., J., Sinke J., Ypma M., S., de Vries T., J., Wittenberg Th. "Towards technology readiness of Fiber Metal Laminates", Glare Technology Development (GTO) 1997-2000. [2] Krishnakumar S. "Fiber Metal Laminates -The synthesis of metals and composites", Materials and Manufacturing Processes, Vol. 9, No.2, 1994, pp. 295354. 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