In this study three factors affecting stress distribution in horizontal axis wind turbine blade are studied using ANSYS Fluid-Structure Interaction (FSI) simulation. The first factor is the cross-section of the wind turbine blade which is selected to be an airfoil. The second factor is the twist angle of the blade while the third factor is the material. A study of two different airfoils is made for three different blades' twist angles and two different materials to obtain the results of total deformation, stress distribution and maximum equivalent stress (von-Mises) along the blade length. This study emphasizes the importance of a multi-disciplinary research where computer, mechanics, and materials engineering are involved. The fields Computational Mechanics, Mechanical Design and Materials Engineering are used in the analysis of wind turbine blade in this study. Also understanding in depth the stress distribution in wind turbine blades could improve the design of wind turbines and lessen the cost of the clean wind energy.