Abstarct: The main goal of this dissertation is prediction of the tensile strength of graphene-reinforced polymer nanocomposite using shear-lag and cohesive zone models. An RVE of nanocomposite which consisting of graphene, polymer matrix and the cohesive interface is considered. An analytical procedure is extended baxsed on the elasticity to survey the interfacial damage and debonding growth between the graphene and polymer matrix. The interface behavior according to the amount of applied stress has three states: entirely intact, damaged (including intact and damaged parts) and debonded (including intact, damaged and debonded segments). By using analytical derived relations, the distribution of axial stress of graphene and interfacial shear stress at the three mentioned states of the interface are studied, and the applied stress to the nanocomposite that leads to damage and debonding initiation at the interface is evaluated. In addition, a sensitivity analysis is performed and the effects of graphene length, interfacial shear strength and graphene volume fraction on the axial stress of graphene, damage and debonding threshold stress along the interface and interfacial shear stress are studied. Then the growth of the damaged and the debonded zones along the interface is examined. In contrast with available numerical studies, in the present study, the tensile behavior of graphene reinforced polymer nanocomposites is studied using analytical procedure. The main mechanisms which lead to degradation of the mechanical properties are considered the interfacial debonding and the matrix damage evolution. To study the damage progress in the epoxy matrix, an elastic damage model is employed using Lemaitre damage evolution law. In addition, in order to verify the analytical results, an experimental study is performed to obtain stress-strain curve as well as the ultimate tensile strength of the nanocomposites. Also a loading-unloading test was accomplished to evaluate damage parameter for epoxy polymer baxsed on the variation of the elastic modulus and the corresponding materials constants of Lemaitre damage evolution law for epoxy were determined.