Modeling and Simulation of Hydrogen Storage Tanks Fabricated from Composite Materials Bahaa M. Kamel * , Mohamed I El-Anwar ** , Mahmoud G. El-Sherbiny *** and Nihad M. El-Chazly *** *Post Graduate Student, Mechanical Engineering Dept, National Research Centre, Giza, Egypt. **Assistant Professor, Mechanical Engineering Dept, National Research Centre, Giza, Egypt. ***Professor, Mechanical Design and Production Dept, Faculty of Engineering Cairo University, Giza, Egypt. ***Professor, Mechanical Engineering Dept, National Research Centre, Giza, Egypt. Abstract: Use of polymer composites in manufacturing hydrogen storage tanks, allows minimizing the weight, improving the aesthetic and also increasing the pressure vessel mechanical, impact and corrosion behavior. In this study, cylindrical composite pressure vessels constituting of metallic internal liner and filament wound composite material as the outer shell were investigated. A Finite Element Method was used to predict the mechanical behavior of pressure vessels, via specially developed model. The influence of; metallic and composite layers thicknesses, number of composite layers and winding angle of filament-wound composite, were tested. A parametric study shooting minimum tank weight and cost was done to find out the optimum tank design. Keywords: Finite Element, hydrogen storage, tanks, design, ANSYS, composite Introduction: Filament-wound composite pressure vessels have found widespread use not only for military use but also for civilian applications. Cylindrical composite pressure vessels constitute of a metallic internal liner and a composite outer shell [1] as shown in Fig1. The metal liner is necessary to prevent leaking, low permeability of hydrogen, while some of the metal liners also provide strength to share internal pressure load [5, 6]. Fig 1: Hydrogen tank and example of its wall materials layers J.C. Velosa and J.P. Nunes [7] studied the development of new generation of filament composite pressure vessel by using High density polyethylene (HDPE) liner and thermosetting resin as matrix with 70% mass fraction of 2400 Tex type E continues glass fiber. The ABAQUS F.E. package was used to predict the mechanical behavior of the cylinder in the range from 6 to 18 bars. Finally it was found that failure occur in some cross-ply internal layers having fibers oriented at 20 at lower vessel internal pressure. Bryan C.Lung [8] studied the detected damage of pressure vessels with little or no maintenance required. To meet the need for a safe, reliable fuel storage system, a