OICC Press Journal of Solid Mechanics 2008-7683 10 2 2018 06 30 Analytical Solutions of the FG Thick Plates with In-Plane Stiffness Variation and Porous Substances Using Higher Order Shear Deformation Theory 315 325 EN M karimi darani Department of Engineering, Colleg of Engineering, Fereydan Brabch , Islamic Azad University, Isfahan, Iran A Ghasemi Department of Engineering, Colleg of Engineering, Fereydan Brabch , Islamic Azad University, Isfahan, Iran Journal Article 2018 06 30 This paper presents the governing equations on the rectangular plate with the variation of material stiffness through their thick using higher order shear deformation theory (HSDT). The governing equations are obtained by using Hamilton's principle with regard to variation of Young's modulus in through their thick with regard sinusoidal variation of the displacement field across the thickness. In addition, the effects of the substances in FG-porous plate are investigated.